cell biology

peroxisomes function

Contain oxidase enzymes that detoxify alcohol, hydrogen peroxide, and other harmful chemicals, break down fatty acids and transfer hydrogem from compounds to oxygen to eventually form water

daily, 100nmoles of T4 is produced and about 5 nmoles of T3. but T3 is 3-8 times more effective. only 0.4% of T3 and 0.04% of T4 are unbound in the blood. of the 100nmoles of T4, 35nmoles is converted to active T3 and 45nmoles is converted to rT3, 20nmoles is lost in bile

T3 has a half life of 24 hr T4 has a half life of 7 days rT3 has a half life of 5 hr

hormone definition

chemical messegner, synthesised by specialised cells, secreted into the bood in small amounts which acts of a specific receptor in target organs to regulate ceullar function. hormones act on target cells by binding to specific receptors located either on the cell surface or within the cell.

endocytosis

clathrin-coated vesicles move substances into the cell from outside by budding from the plasma membrane. 3 processes can then occur: - recycling the material - degradation of the material - transcytosis (movement of the material from the basal membrane to the apical membrane)

nucleus function

contains the main genome, where DNA and RNA synthesis take place

types of hormone release

continuous - continuously released pulsatile - released in bursts circadian - cyclical exocytosis - on demaned

drugs and diseases that affect transmission

curare - blocks acetylcholine receptors on the postsynaptic membrane, causes paralysis botulinum - inhibits the release of acetylcholine into the synaptic cleft myasthenia gravis - autoimmuni disorder where antibodies destroy acetylcholine, treatment is to give inhibitors of acetylcholinesterase

cell surface receptors

hydrophilic signalling molecules cannot cross the membrane and must bind to the cell surface membrane examples: - ion channel coupled - multi pass transmembrane proteins that form a channel, they alter the membrane permeability to ions. they convert the chemical signal to electrical signals in nerve synapses as the binding of the ligand cause a conformational change in the receptor. - G-protein coupled - large transmembrane proteins (pass through the membrane 7 times) which interacts with larges trimeric proteins that contain alpha, beta and gamma. they mediate a large range of signalling and biological processes. G-proteins tranduce signals by binding to other target proteins on the plasma membrane

growth hormone replacement (rhGW) therpay can be induced if someone has a growth hormone deficiency

hypopituitary - reduced action growth hormone excess in adulthood can cause: - enlarged jaw, hands and feet - growth of lips, nose and skin above the eyes - growth of viscera - impaired glucose tolerance # the person will not grow taller growth hormone excess from childhood affects the gonads so growth doesnt stop when it should and the person continues to grow taller for longer

control of the ovarian cycle

important hypothalamic hormone: - gonadotropin releasing hormone (GnRH), the release is pulsatile and a high frequency causes LH release and low frequency causes FSH release. important pituitary hormone: - follicle stimulating hormone (FSH) which stimulates recruitment and growth of immature folliclues, upregulates CYP19 (aromatase) gene expression and activity, induces expression of LH receptors in granulose cells which is important for the late follicular phase, it prevents apoptosis/atreisa of antrol follicles. - luteinising hormone (LH) which acts on theca cells to promote andorgen production - the surge that lasts 1-2 days is what triggers ovulation, it also acts on granulose cells to stimulate production of progesterone and maintains the corpus luteum. important ovarian hormones: - oestrogens which prepare the reproductive tract for potenital fertilisation and pregnancy, the dominant hormone secreted pre-ovulation - progesterone which promotes uterine and uterine tude secretions to maintain and support potential fertilisation and implantation of an egg and it is the dominant hormone secreted post-ovulation - inhibin A and B which are secreted by granulose cells and reperess FSH secretion.

impact of hypothyroidism can be treated by giving synthetic T4 - Levothroxine

infants: - decreased mental capacity - short stature children: - decreased mental capacity and growth in adults: - tiredness -bradycardia - mental slowness - cold intolerane - weight gain - depression (50% of cases) - dry skin - puffy hands and face

zona glomerulosa

lacks 17 alpha-hydroxylase enzyme so cannot produce cortisol and androgens ONLY hormone it can produce is aldosterone

LUCA

last universal common ancestor, all life forms can be traced back to the basic microorganisms.

velocity sedimentation

separates cells based on density

centrifugation

separates components based on size large parts - whole cells, nuclei and cytoskeleton small parts - ribosomes, large macromolecules, small vesicles and viruses

active transport

- coupled transport/ co transport - ATP driven transport - light or redox driven transport

aldosterone hormone

- a major mineralocorticoid (influences salt and water balances) - 50-70% is bound to albumin in plasma - half-life of 15-20 minutes - its primary action is on kidney, colon, salivary glands - it binds to mineralocorticoid receptors within principal cells and upregulates ENaC and Na+/K+ ATPase to increase sodium reabsorption by 1.6% which equates to about 3.5L of fluid per day.

effects of thyroid hormones

- act to increase the responsiveness of cells to other hormones - they are important in maintaining normal mood - the do not have single specific target tissue - they have an important role in both neural and skeletal development

Cortisol as a glucocorticoid

- anti-inflammatory and immunosuppression effect by inhibiting cytokine production and T cell production, as well as inhibiting prostagladin and leukotriene production by inhibiting lipocortin-1 which decreases the function of phospholipase 2 and cyclooxygenase which are invovled in the process of producing prostaglandins and leukotrienes.

classes of hormone: peptide

- between 3 and 332 amino acids in length - synthesised as preprohormones so part of the chain is cleaved off to produce the functioning hormone - stored prior to release - act on cell surface G-protein receptors then via 2nd messenger systems to cause effect in target cells

restricting protein movement

- formation of complexes - the whole complex must move as one so the proteins cannot travel individually - attached to the cytoskeleton - involved in cell-cell interactions (vital in the immune system)

impact of hyperthyroidism

- heat intolerance - weight loss - warm moist skin - tachycardia (atria fibrillation and heart failure) - fine tremor of fingers graves disease - autoimmune condition in which auto-antibodies stimulate the TSH receptor, a stare, bulging eyes, goitre (enlgarged thyroid due to large stimulation)

cortisol is a stress hormone, we produce most in the morning when we are waking up, other things that cause stress trigger the hypothalamus to release CRH which act in the anterior pituitary to cause corticotrophs to release ACTH. this then acts on the cortex of the adrenal glands to stimulate cortisol production and release.

- major glucocorticoid - >90% bound to plasma proteins - half-life 60-90 minutes - effects virtually all tissues mainly by binding to its receptors and controlling gene transcription.

some repsonses need a combination of signals so signalling pathways can interact

- more than one signal may target the same intracellular protein e.g post translational modifications - two separates signals may activate two separate intracellular proteins which then work together and form a complex. - pathways can integrate so once signal induces another

classes of hormone: amino acid

- most synthesised from tyrosine - stored for instant release - they have different modes of action (some act as peptide hormones and some as steroid hormones depending on their chemical makeup)

cortisol function

- stimulates hepatic gluconeogenesis - inhibits glucose uptake in mucle and adipose tissue - stimulates muslce catabolism - inhibits bone formation - leads to loss of collagen and connective tissue - increases vascular sensitivity to epinephrine and norepinephrine - can modulate behaviour and cognitive function - inhibits gonadal release of testosterone, oestrogen and progestins

the archezoa hypothesis would fail if we find:

- the archezoans branch among aerobic species with mitochondria - mitochondrial gene on archezoan genomes - mitochondrion-derived organelles are present in archezoans

anterior pituitary hormones - release hormones into the systemic circulation. release controlled ny hypothalamic hypophysiotropic hormones in portal hypophyseal vessels

- thyotrophs release thyroid-stimulating hormone (TSH) this stimulates thyroid hormone release - gonadotrophs release follicle-stimulating hormone (FSH) which stimulates sex steroid production gonadotrophs also release luteinizing hormone (LH) which stimulates sex steroid production - corticotrophs release adrenocorticotrophic hormone (ACTH) which stimulates cortisol release - somatotrophs release growth hormone which stimulates growth - lactotrophs release prolactin which stimulates milk production

resting membrane potential

-70mV maintained by the high permeability of the membrane to K+ and the active transport of Na+ across the membrane

control of hormone effects

-modification -degradation -receptor down-regulation -termination of intracellular effects -negative feedback by the regulated metabolite, the hormone itself or by the trophic hormone release by the pituitary.

function of th thyroid gland

-plays an important role in regulating metablism and body weight - it increases cardiac output and systolic pressure (heart rate & stroke volume) - it controls glycolysis, oxygen consumption and thermogenesis and overall basal metabolic rate - it is important in maintaining emotional tine and improves alertness, memort, reflexes and wakefulmess. - it is essential for foetal neural development and bone growth after birth -

mini endplate potential

0.5 mV, they occur randomly when the muscle is at rest, it is when 1 vesicle of acetylcholine fuses with the membrane and either release all of its contents or none. according to this 50 vesicles would need to release their contents but 200-300 do, this extra margin is known as the safety factor

muscle contraction steps

1) Motor neuron releases acetylcholine into the neuromuscular junction and causes the depolarization of the sarcolemma. 2) Depolarization spreads down the sarcolemma to the T-tubules, triggering the release of Ca2+ ions. 3) Ca2+ binds to C subunit of troponin, causing a shift in tropomyosin and exposure of the myosin-binding site on the actin filament. 4) Shortening of the sarcomere occurs as the myosin head binds to the exposed sites of actin, forming a cross-bridge and hydrolyising ATP to ADP and Pi. it pulls the actin filament along the thick filament, known as the powerstroke, resulting in contraction. 5) ATP binds to myosin head, releasing ADP and Pi, allowing it to relax from actin. the cycle continues if there is Ca2+ and ATP present.

1. uniport 2. symport 3. antiport

1. carrier protein that transports one molecule. e.g. GLUT, a family of glucose transporters 2. transports two molecules in the same direction 3. transports two molecules in opposite directions

3 phases of an action potential

1. depolarisation - voltage gated Na+ ion channels open, Na+ ions diffuse into the axon, at -55mV Na+ activation gates open. soon after K+ ion channels open and K+ ions diffuse out of the cell. 2. repolarisation - time dependent Na+ inactivation gate closes stopping the diffusion of Na+ ions into the axon, K+ ion channels still open so K+ diffuses out of the axon hyperpolarisation - K+ diffuse out of the cell and voltage reaches below -70mV. time dependent Na+ activation gate closes. when all ion channels are closed the Na+/K+ ion pump can restore resting membrane potential.

different types of cell signalling methods (from short distance to long distance)

1. gap junctions - pores between two adjacent cells, molecules travel through the connexon hemichannel 2. contact dependent - nothing is secreted, the signalling molecule is on the cells surface and it interacts directly with the receptor on the recipient cell. important for immune signalling & development 3. autocrine signalling - the cell binds to the signal it has secreted, other cells of the same type can also bind to the signal 4. paracrine signalling - local mediators act on different cell types in close proximity. important during development 5. synaptic - neurones/ action potentials 6. endocrine - hormones in the bloodstream

1. subthreshold EPSP 2. suprathreshold EPSP

1. graded potential doesnt reach the threshold when it enters the axon hillick trigger zone 2. graded potential is at or above threshold when it enters the axon hillock trigger zone, leads to an action potential

receptors on the post synaptic membrane work by two mechanisms

1. ligand-gated ion channels - inotropic or ionotropic receptors. these are fast acting as only opens the ion channels examples - acetylcholine, glutamate (most important EPSP generating neurotransmitter in the brain), GABA (most important IPSP generating neurotransmitter in the brain, glycine 2. G-protein coupled receptors that activate second messenger systems - metabotropic receptors. these are slow acting, the second messenger that is activated can either alter the state of open ion channels or modify proteins/ regulated the synthesis of new proteins examples - adrenaline, histamine, cholecytokinin, ATP, acetylcholine some receptors can be both

observing proteins diffusing in the plane of the membrane

1. observing a hybrid cell containing mouse cell proteins and human cell proteins, use fluroscent markers to view movement. the human and mouse proteins diffuse across the whole of the cell over time making the difference indistinguishable 2. FRAP - bleach a plasma membrane surface with a laser beam to destroy a label, observe recovery if a label was applied to a molecule that diffuses easily.

entrpoy - two key trends for reactions

1. order tends to disorder 2. high enthalpy tends to low enthalpy

1. endogenous 2. exogenous

1. originates from the cell itself 2. originates from outside the cell

switching signals off

1. removal/ inactivation of signal - by degradation, recycling (reuptake) or sequestration (act of removing or separating). some signals are removed faster than others 2. removal/inactivation of receptor - desensitisation allows cells to become adapted to a constant signal 3. inactivation of activated signalling proteins - dephosphorylation/ phosphorylation or GTP hydrolysis to switch off G-protein, association with an inhibitor or dissociation from activator 4. degradation/ removal of second messengers - removal of cAMP and cGMP by hyrolysis

types of signalling complexes

1. stable - the components of the signalling pathway are linked by a scaffold protein - quick activation as all in the same place 2. transient - the signalling complex assembles after the receptor is activated or the signalling complex assembles on phosphorylated docking site

what happens at a neuromuscular junction

1. the action potential reaches the presynaptic knob and the depolarisation of the membrane causes the opening of voltage gated Ca2+ ion channels 2. Ca2+ ions diffuse into the axon temrinal, the increase in Ca2+ ions causes the vesicles to fuse with the presynaptic membrane 3. the vesicles release neurotransmitter into the synaptic cleft by exocytosis 4. the nuerotransmitter diffuses across the cleft and binds to receptors in the post synaptic membrane and causes ligand gated ion channels in the postsynaptic membrane to open and ions diffuse into the postsynaptic cell (muscle endplate)

G-protein linked receptor signalling via cAMP

1. the signal binds to the receptor, this causes a conformational change, the alpha subunit releases GDP and binds GTP and then dissociates from the beta and gamma subunits 2. the alpha subunit binds to adenylyl cyclase and activates it, the alpha subunit hydrolyses GTP and then reassociated with the beta and gamma subunits. 3. enzyme generates cAMP from ATP 4. cAMP dependent protein kinase A is activated 5. protein kinase A phosphorylates the protein which leads to a cellular response, it also amplifies the signal

function of membrane proteins

1. transporters - move nutrients, metabolites and ions across the membrane 2. linkers - join membranes to intracellular or extracellular macromolecules 3. receptors - transduce signals from the environment 4. enzymes which catalyse reactions at membrane surfaces

cortisol and androgen production in the zona reticularis and the zona fasiculata

1/ ACTH binds to its receptors and it activates adenylate cyclase which converts ATP to cAMP and the second messenger pathway begins. 2/ protein kinase A activates cholesterol ester hydrolase by phosphorylation which breaks down the cholesterol storage in the cell. protein kinase A increases the production of enzymes involved in steroid synthesis and protein kinase A increases StAR protein actions that helps move cholesterol into mitochondria. 3/ when in the mitochondria the cholesterol is actived on by P450 enzymes. 4/ lack the P450aldo gene so aldosterone cannot be formed so all the cholesterol forms cortisol and androgens

structure of the adrenal glands

1/ capsule 2/ cortex 3/ medulla

acute actions of growth hormone

1/ causes the release of fatty acids from adipose tissues and enhances their conversion to acetyl-CoA 2/ it reduced glucose metabolism and uptake into cells (classed as a diabetogenic hormone) 3/ increases gluconeogeneis in the liver 4/ increases the production of the insulin-like growth factor direct effects are anti-insulin

Release of thyroid hormones

1/ endocytosis from the colloid into the follicular cell, part of the colloid cell buds off into the follicular cell and it contains the thyroid hormone 2/ lysozymes break down the thyroglobulin to produce a mixture of thyroid hormones. therefore this process is not selective so there is T1,2,3 and 4. T1 and T2 are recycled. 3/ T3 and T4 are lipophilic so can cross the membrane into the blood. they bind to thyroid binding proteins in the blood. only avery small amount is not bound - which is the only able to bind the receptors.

synthesis of thyroid hormones

1/ follicular cells produce thyroglobulin and it is moved into the colloid 2/ iodine moves from the blood, across the follicular cells into the colloid via a sodium coupled iodine transported between the capilarry and the follicular cell. 3/ iodination occurs in the colloid by the enzyme thyroperoxidase 4/ coupling occurs by the same enzyme, mostly T4 that is produced.

long term effects of growth hormone (via IGF-1)

1/ growth promoting action of bone, epiphyseal cartilage, soft tissue, gonads and viscera 2/ promotes amino acid uptake and protein synthesis 3/ insulin-like endocrine effects on tissues long-term effects mimic insulin

action on receptors & 2nd messenger: peptide & amino acid hormones

1/ hormone binds to a receptors coupled with a G protein which then activates second messengers such as; cAMP, cGMP, Ca2+, diacylglycerol and IP3. 2/ second messenger activates third messengers, ie protein kinases. this is reversible as phosphorylation is reversible there are multiple physiological responses: rapid - transporter protein activation or inhibition short-term - general metabolism, neurotransmitter synthesis/ release and receptor sensitivity long-term - regulation of gene expression

preparation of a buffer

1/ mix a large volume of a weak acid with its conjugate base 2/ mix a large volume of a weak base with uts conjugate acid

what determine rate of a reaction?

1/ temperature, higher temp means average kinetic energy increases so more molecules exceed the activation energy 2/ (enzymatic) catalysis - lower the activation energy so more molecules exceed the activation energy 3/ concentration - as the conc increases the same fraction of molecules have KE greater than the activation energy but as there are overall more particles a greater number exeed the activation energy

zones of the cortex #cannot live without it without treament involved in long term modulation

1/ the zona reticularis (inner zone closest to the medulla) - has compact cells which contain less lipid (makes up 10%) and produces cortisol and androgens 2/ zona fasiculata (the biggest) - contains large lipid containing cells (makes up 75%) and produces cortisol and androgens 3/zona glomerulosa (outermost layer) - this produces aldosterone and is about 15% of the cortical volume. the zones contain different enzymes which can convert cholesterol to different molecules in the early stages to produce different steroid hormones.

3 major thyroid transporting proteins

1/ thyroxine-binding globulin carries most of T3 and T4 (~70%) and binds both with a high affinity. 2/ thyrosxine-binding prealbemin has a greater affinity for T4 and carries ~10% of it 3/ albumin carries ~15% of T3 and T4, it has rapid dissociation which makes it a major source of free hormone to tissues

water dissociation

2H2O => H3O+ + OH- the ions are highly reactive H3O+ is commonly called H+ for simplicity but free H+ ions do not exist in water

cell cycle checkpoints

3 checkpoints in G1, G2 and M phase G1 - checks if the cell is big enough, if the DNA is damaged, if the environme t is favourable G2 - is DNA replication complete and correct M - all chromosomes attached to the spindle the checkpoints are regulated with cyclin-dependent kinases (Cdk)

the mole

6 x 10^23 atoms in a mole

polyribosome

A group of several ribosomes attached to, and translating, the same mRNA molecule.

Microstate

A microstate is one of the huge number of different accessible arrangements of the molecules' motional energy* for a particular macrostate. *Motional energy includes the translational, rotational, and vibrational modes of molecular motion. for no units of energy there is still one accessible microstate - the minimum entropy of the system, 0. eg. you have 3 units of energy and 3 molecules you can either give all three units to any one of the moelcules, give 2 units to one then 1 units to another and no energy to the last or give each moelcules or unit of energy each and the different ways in which the energy can be shared is the numbr of microstates. a system will change between accessible microstates over time use the boltzmann formula to work out the number of accessible mircostates.

cholesterol

A molecule found within the cell membrane that modulates how permeable the membrane is, the higher the % of cholesterol, the less permeable the membrane is to water soluble molecules

phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells, it is regulated by actin as they form the pseudopods that engulf the pathogen in bacteria.

EPSP/IPSP

EPSP - excitatory postsynaptic potential IPSP - inhibitory postsynaptic potential

G0 in cell cycle

G0 (quiescence) is a pause in the cell cycle, it occurs G1 where a cell can stay in a paused period which can last indefinitely, this causes variation in the length of cell cycle.

Cell cycle (G1, S, G2, M)

G1 - where main growth occurs, the cell is recovering after cytokinesis and prepares the cell for DNA synthesis, the organelles are replicated S - synthesis of DNA, all the chromosomes are replicated as well as proteins associated with DNA replication G2 - check points for errors before mitosis occurs, growth phase M - mitosis

intercellular communication

GAP junction -vcell to cell, specificity depends on anatomical location, cells act as one. found in syncytial tissues (e.g heart tissue) synaptic (nervous system) - message transmitted across synaptic cleft, depends on anatomical location and receptors. paracrine (to local cells) & autocrine (to itself) - message transmitted by diffusion in interstitial fluid, specifity depends on receptors endocrine system - message transmitted by circulating body fluids, specifity depends on receptors

RTK mediated activation of the RAS-MAPK pathway

Grb-2 binds to the activated RTK complex, RAS and GEF do not bind directly to the RTK. Grb-2 leads to the recriutment of GEF proteins which helps the small monomeric RAS protein hydrolyse GTP - this is then in an active formation for downstream signalling.

blood as a buffer (pKa of 6.1)

H2CO3 <=> H+ + HCO3- add strong acid -> HCO3- + H+ <=> H2CO3 add strong base -> H2CO3 + OH- <=> HCO3- + H2O

HA <=> H+ + A-

HA = weak acid A- = conjugate base

Kinetic energy equation

KE=1/2mv^2 average kinetic energy depends on the temperature 3/2Kb*T

RAS and cancer

RAS is a proto-oncogene, mutations of RAS are found in about 20-30% of human cancers. most common RAS mutations prevents the hydrolysis of GTP so it stays bound to GTP more tightly and the signalling pathway is continuously switched on - driving proliferation

RAS activates a downstream phosphorlation cascade - map kinase pathway many different MAP-kinase pathways that are activated by different monomeric G-proteins

Raf is recruited to the cell membrane, it binds to Ras and activates it, Raf then activates its downstream target Mek, this activates Erk and Erk then translocates into the nucleus and phosphorylates its various targets (MAPs). Ras=>Raf (map kinase x3)=>Mek(map kinase x2)=>Erk(map kinase)

The Boltzmann formula is S = k ln W.

S = entropy K = the boltzmann constant - 1.3 x 10^-23 JK^-1 W = number of accessible microstates

Maxwell-Boltzmann distribution

The distribution of energies (and therefore speeds) of the molecules in a gas or liquid. most particles have a similar speed but some have very high speed and some have very low speed. particle speed depends of mass and temperature

cytosol function

The fluid portion of the cytoplasm, excluding organelles and other solids. where many metabolic pathways occur e.g protein synthesis

turgid pressure

The pressure that water molecules exert against the cell wall. placing a blood cell in salt water - more ions hit the membrane on the outside of the cell than the inside so the water is forced out of the cell, theres a net pressure on the cell. therefore turgid pressure is caused by more ions on one side of the membrane

equilibrium constant expression Kc

[products]/[reactants] it is fixed for a given temperature if K1 is the forward rate and K-1 is the backwards reaction rate = K1[A][B] rate = K-1[AB] make them equal and you can rearrange to form [AB]/[A][B] Kc is useful because: - tells you what you have in the beaker at equilibrium - if Kc >> 1 - you have mostly product - if Kc << 1 - you have mostly reactant - if Kc ~ 1 - equal parts Kc doesnt depend on transition states or rate limiting steps as it balances out at equilibrium between the forward and back reactions

glycocalyx

a coating of the cell membrane in some cells, made up of glycoproteins and glycolipids. Function: - it protect the cell against chemical, physical and biological damages - cell adhesion molecules (carbohydrate binding proteins on other cell surfaces or in extracellular matrices - recognition of glycosylation patterns on other cells - storage (bind and release growth factors)

spectrin

a cytoskeletal protein that lines the intracellular sid eof the plasma membrane in eukaryotic cells, it is a platform for membrane channels, receptors and transport. forms pentagonal and hexagonal arrangements, the hexagonal arrangements are formed from tetramers of specrin subunits associating with short actin filaments at either end of the tetramer

the nernst equation

a mathematical relationship used to calculate an ionic equilibrium potential an electrical gradient is set up in the opposite direction to the concentration gradient as +ve K+ ions that have moved out of the cell become attracted to the slight -ve charge inside the cell so they begin to move back in. at the equilibrium potential that electrical gradient and concentration gradient are equal and opposite. the sum of all the equilibrium potentials is equal to the resting membrane potential

hypothalamus

a region of the brain which plays a key role in homeostasis

plasma membrane what is it?

a selectively-permeable phospholipid bilayer which encloses the organelles within the cell. lipids are the major component (about 50% by mass). membrane proteins regulate the transfer of molecules across the membrane

relative refractory period

a stronger than usual stimulus is necessary to initiate an action potential, but the membrane is capable of generating another action potential. Na+ ion channed have recovered, some K+ ion channels are open

necrosis

accidental cell death due to injury where the cells swell and become leaky. this triggers te inflammatory response where lots of immune cells arrive to attack the cell and lots of liquid is brought to the site, this can cause more issues.

acid and base definitions

acid - substances with produces H+ ions by dissociation base - releases OH- ions

acid dissociation constant, Ka

acids dissociate to form an equilibrium with their conjugate base. the equilibirum constant of a weak acid or base is known as the acid dissociation constant.

effects of abnormal adrenal hormone production

addisons disease: - primary adrenocorticoid insufficiency - 80% autoimmuni with adrenal atrophy with the remainder a result of infection, malignancy or medication causes: cortisol deficiency: - weakness - fatigue - anorexia - hypoglycemia mineralocorticoid deficieny: -excessove renal Na+ loss - dehydration - hypotension - hyponatremia - hyperkalemia - acidosis

long-term potentiation (LTP)

an increase in a synapse's firing potential after brief, rapid stimulation. Believed to be a neural basis for learning and memory. the main reason a computer cannot function exactly like a brain is because it cannot restructure neuronal circuits as a result of sensory inputs.

Node of Ranvier

area of unmyelinated axon which occurs every 1-2mm and are 1 micrometer wide. there's a high density of Na+ channels and they allow saltatory conduction to occur.

equilibrium constant of water Kw Kw = [H+][OH-] it is equal to Kc = [H+][OH-]/[H20]^2 as water is vastly in excess so [H20] in reactions doesnt change

at 25 degrees Kw = 1.0 x 10^-14 M^2

3 main types of cell

bacteria archaea eukaryotes

Receptor Tyrosine Kinases (RTKs) - includes insulin receptor and many growth factors, growth factors control cell differentiation and proliferation

best known group of enzyme-linked receptors. the binding of the ligand to the receptor leads to cross-linking of two receptor chains. then cross-phosphorylation/ autophosphorylation occurs. phosphorylated residues provide docking sites for other signalling proteins

G-protein linked receptor signalling via phospholipase 3 secondary messengers: - IP3 (soluble and enters the cytosol) - releases Ca2+ from the endoplasmic reticulum DAG (remains embedded in the membrane) - activates protein kinase C

cC1. signal binds to the recepter => conformational change, alpha subunit releases GDP and binds GTP and dissociates from beta and gamma subunits 2. alpha subunit binds to phospholipase C and activates it, hydroplyses GTP to GDP and then reassociates with the beta and gamma subunits 3. membrane phospholipid is cleaved by phospholipase C to produce DAG and IP3 4. DAG activates protein kinase C which phosphorylates proteins.IP3 causes the release of Ca2+ ions (from the ER) from organelles, protein kinase C is only activated in the presence of DAG and the Ca2+ ions

transporter proteins (carrier/ channel)

carrier - binds solute on one side of the membrane and moves it by a conformational change channel - form hydrophilic pores in the membrane through which solutes can diffuse

regions of a neuronal cell

cell body dendrites axon axon terminal

laws of thermodynamics: first law

deltaU, change in the internal energy of a system, equals to the energy transfer to the system by work, plus the energy transfer to the system by heat. deltaU = w + q the energy released by a chemical reaction will: - transfer heat to its surroundings - do work on its surroundings biomchemistry is done in open containers, not closed pistons (as no pressure). to measure internal energy change measure the heat released by a reaction as this is easy to measure, use an open testube and insulator of polystyrene (calorimeter).

Velocity of an action potential

depends on diameter of neuron and mylenation. the larger the diameter, the more room for the local current flow in current loops. the higher the membrane resistance, the less current is lost by leaking out of the cell and so more current stays in the current loops velocity is directly proportional to the square root of axon diameter X membrane resistance.

autophagy

destruction of defective cell material. important during normal cel growth

endothermic and exothermic

endothermic - reaction absorbs energy so deltaU > 0, example is protein synthesis (amino acids => protein) exothermic - reaction that gives out heat energy so deltaU < 0

cytoskeleton - intermediate filaments

diameter - 10nm provide mechanical strength to the whole cell (including nucleus). prvent excessive stretching of the cell. those in the cytoplasm vary with each cell type and organisms with a hard exoskeleton do not have them. filaments in the nucleus are called nuclear lamins (LMNA, LMNB, LMNC), they form a meshwork lining the inner membrane and act as an anchoring system for the chromsomes and the nuclear pores. structure - alpha helical coiled coil which coils into dimers, two dimers make a tretramer and 8 tetramers associate to form the filament. the N-terminus and C-terminus for globular ends.

cytoskeleton - microtubules

diameter - 25nm involved in organelle and vesicle shuttling and they facilitate movement, moving chromosomes during cell division and driving cilia and flagella. structure - globular monomers callued tubulins which use GTP to build up. the protein subunit is an alpha and beta tubulin dimer. motor proteins - kinesins and dyneins, these proteins have a head and tail region and the head region binds to ATP, hydrolysis of the ATP then drives the kinesins towards the positive end of the microtubule and the dynesins towards the negative end of the microtubule, the tail end binds to the cargo. it can be synthesised and broken down rapidly which is useful in separation of chromosomes.

cytoskeleton - actin filaments

diameter - 6-8nm found on the edges of the cell and help the cell to maintain its shape, they are the most abundant of the components. structure - a helix of actin monomers. the filament is polarised, monomers of the globular actin bind to either end of the filament but more rapidly at the positive end. motor proteins - myosin which have globular heads that bind to ATP and the head binds to the actin filament then the hydrolysis of the ATP drives the movement. the tail end of the myosin binds to the cargo. myosin I - in all cells and in a single myosin molecule which moves cargo along the filament myoson II - found in muscle cells, useful in contraction of muscle cells

Speed of diffusion

diffusion is good over short distance scales but not long distance scales because diffusion is most effective during the mean free path as it is not hit by other molecules that may alter its path

mean free path

distance a particle travels between collisions

divergence and convergence in neurones

divergence - one neurone branches to a number of postsynaptic neurones via colateral axons convergence - many presynaptic neurones converge to one postsynaptic neurone

angiotensinogen control of aldosterone

drop in blood pressue detected by the kidneys which then produce renin into the blood stream. renin converts angiotensinogen (produced by the liver) to angiotensin I (by removing some amino acids) which is then converted to angiotensin II by ACE found in the blood vessel endothelium. angiotensin II has many effects one of which is to stimulate the production of aldosterone in the adrenal cortex to promote Na+ reabsorption.

different cells repsond differently to the same signal

due to: - using different receptors e.g - acetylcholine and a nicotinic ion channel linked receptor leads to membrane depolarisation but acetylcholine and a muscarininc G-protein linked receptor leads to hyperpolarisation - activation of different cellular machinery e.g. - acetylcholine in pancreatic acinar cells induces the secretion of digestive enzymes as a secondary messenger response is triggered (protein kinase) but in endothelial cells nitric oxide is secreted which relaxes muscles, this is because NO synthase is activated by the Ca2+ release

female reproductive system

egg moves from the ovary, is gathered by the fimbriae and then moved through the fallopian tube (oviduct) towards the uterus (has a endometrium lining which is where embryo implants and the myometrium lies underneath the endometrium). fertilisation usually occurs in the oviduct and moves towards the uterus

endocrine system definition

endocrine cells within endocrine glands release substances (hormones) which are conveyed by the blood stream and act on distant cells

vesicular transport

endocytosis and exocytosis inside and outside the cell. for transport between organelles donor compartments are used which buds off the donating cell and then fuses with the recipient cell. different vesicles can be coated by different proteins to move proteins to different parts of the cell. A is clathrin - exit from golgi and endocytosis B is COPI - within the golgi body C is COPII - involved with the ER

in the blood plasma T4 can be converted to T3 by taking off an iodine group as T3 is more biologically active. step up - produces active form of T3 step down - produces inactive form of T3

enzymes which can make T3 from T4 - 1 5'-deiodinase which is most abundant, provides T3 to plasma and this is step up - 2 5'-deiodinase which is found in the brain and pituitary is a step up - 3 5'-deiodinase is a step down as it converts T4 to rT3 which is inactive

eukaryotic cells as chimeras

eukaryotic cells are chimeras, this means they are at least 2 different cells that have come togetger to form a single cell, the genome and membrane of the eukaryotic cell are chimeric in nature too - the two origins are endogenous and exogenous.

exponentials and logarithms

exponentials - they are shorthand for multiplication exponential growth arises when you have a constant replication rate logs - the inverse of exponents useful for measuring quantities that vary over a huge range x = log10(y) - log 10(z)

negative feedback mechanism

feedback that causes the stimulus to decline or end

different orders or reactions

first - reaction when one single atom determines to rate, in first order the concentration of the molecule is proportional to the rate second - two molecules must collide. the concentration of the molecule^2 is proportional to the rate. if you have two different molecukes (bimolecular reaction) the reaction is first order with respect to each molecule but second order overall. the order of a reaction can only be found out experimentally or by full knowledge of the kinetic pathway.

gibbs free energy combines the effects of entropy and enthalpy gibbs free energy tells us: - whether a biological process will or will not occur - in which direction a process will proceed - how much useful work is availible from a process

free energy change = enthalpy change - (temperature* entropy change) also tells us the maximum useful work we can extract from a process in an open system deltaG = deltaH - TdeltaS deltaG = (deltaU - w) - TdeltaS

plasma membrane function

function: - barrier -communication with the environment -passage of molecules in and out of the cell -cell growth, shape change, movement and division

glycolipids in the phospholipid bilayer

glycolipids typically face the cytosol and are important for cell recognition, they are located on the apical side of epithelial cells

glycodylated

has a carbohydrate group attached

amphipathic apolar

have both a non polar and polar end, an example is fatty acids molecules in biological membranes. hydrophobic - do not want to interact with water. this is a major driver in protein folding as proteins in aqueous solutions fold so that the hydrophobic region is in the interior

some hormonal key terms

high affinity - hormones are effecting at low concentrations synergistic - the effect of two hormones is greater tgan one alone permissive - the presence of one hormone is necessary for another to have an effect antagonistic - two hormones oppose each others effects competitive - two hormones, similar in structure, compete for the same receptor

luteal phase in overian cycle overview

hormone levels: - FSH levels decrease then rise slightly - LH levels decrease - progesterone increases, peaks then decreases - oestrogen peaks decreases, increases, peaks then decreases. corpus luteum forms which produces high amount of porgesterone which negatively feeds back causing drop in LH and FSH. over the cycle the corpus luteum regresses and progesterone and oestrogen levels fall, the negtive feed back caused by progesterone is therefore lifted and FSH levels rise

late follicular phase of the ovarian cycle overview

hormone levels: - LH levels increase to very high - FSH levels increase to middle - oestrogen decreases to middle - progesterone increases to low the dominant follicle produces losts of oestrogen and this positively feeds back to increase LH production, this is enhanced by the increased production of progesterone. oocyte completes meiosis I and ovulation is triggered. as LH surge ends there is a drop in oestrogen levels

early follicular phase of the ovarian cycle overview

hormone levels: - oestrogen levels increasing - progesteone levels low - FSH levels drop - LH levels higher than FSH but still low oestrogen negatively feeds back on FSH causing levels to drop, the loss of progesterone and higher oestrogen levels increases the frequencyof GnRH pulses and the decreased FSH leads to follicylar atresia leaving one dominant one.

the end of the ovarian cycle overview

hormone levels: - FSH increasing - LH low - oestrogen decreaing - progesterone decreasing the demise of the corpus luteum occurs, the increase in FSH production is due to negative feedback and a crop of antral follicules are recruited ready for the next early follicular phase.

ovulation of ovarian cycle (few hours)

inflammatory cytokines and hydrolytic enzymes eat away at the follicular wall and that of the ovary (causes a rupture) so a hole is formed in the ovary to allow the free egg with its associated zona pellucida and corona radiata (crucial for capture) to be released into the peritoneal cavity. it is captured by the fimbriae. the remnants of the follicle in the ovary go on to form the corpus luteum.

types of membrane proteins

integral membrane proteins and lipid attached proteins can only be released from the membrane using detergent peripheral, membrane associated, proteins can be detached by changing the ion concentration

lysosomes function

intracellular degradation, allows a good healthy cell to be maintained

medulla (10-12% of the adrenal weight) #can live without the medulla involved in fight or flight repsonse

is a highly specialised part of the sympathetic nervous system and its major product is epinephrine

osmolarity = concentration X number of particles

it describes the number of particles per unit volume whereas concentration is based on particle weight

thyroid structure

it is infront of the trachae and is made up of two lobes with connecting isthmus. the right lobe is generally slightly bigger than the left. it has a very rich blood supply, it acts as an iodine trap and collects and stores iodine from the blood. on the backside of the thyroid which faces the trachae there are the parathyroid glands which are embedded within the thyroid (there are 2-4 pairs).

troponin complex

made up of 3 subunits, T, I and C. when the muscle is relaxed the T and I subunits bind to tropomyosin and actin and this blocks the myosin binding site. when the Ca2+ ions bind to the C subunit the myosin binding site becomes exposed and myosin heads can bind to form a cross-bridge.

how buffers cause slight changes in pH

mixture of weak acid and weak base, not much of the weak acid dissociates because it is weak add a strong base -> the OH- ions from the base react with the weak acid to form A- and H20 add a strong acid -> the acid reacts with A- to form weka acid (HA) and base

golgi apparatus function

modification, sorting and packaging of proteins and lipids for organelles, plasma membrane or secretion

amphiphilic

molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments. eg phospholipids in the bilayer

Transport into nucleus

movement between the nucleus and the cytosol is bidirectional and occurs through nuclear pores in the nuclear envelope. the pores allow small molecules to diffuse easily but for the movement of larger molecules specific transport mechanisms must be put in place. the more movement there is between the cytosol and the nucleus, the more nuclear pores there are in the nuclear envelope.

motor neurone structure

multipolar - multiple dendrites emerge from their cell body both motor neurone and interneurone of CNS have this structure

muscle structure

muscle fibers-->myofibrils-->sarcomere. the muscle fibers have many mitochondria and nuclei and the sarcomere causes the myofibrils to appear striped/

cytoskeleton function

network of protein filaments within some cells that helps the cell maintain its shape and is involved in many forms of cell movement

osmolarity

number of ions/ molecules per unit volume

the 4 major thyroid hormone receptors are: - Tyrosine alpha 1 - Tyrosine alpha 2 (doesnt bind T3) - Tyrosine beta 1 - Tyrosine beta 2 all but alpha 2 have a higher affinity for T3. thyroid hormones enter the cell by facilitated diffusion

once inside the cell T3 and T4 can be stepped up or stepped down. the hormone can bind to the DNA to up regulate or down regulate transcription to produce proteins involved in many metabolic pathways. the effect is therefore slow as proteins have to be formed # the key target is increased transcription of genes encoding mitochondrial uncoupling proteins

position of adrenal glands

one above each kidney, about 8-10 grams, made of two types of tissue which produces different hormones. the outer most area is the cortex and the inner is the medulla. about 90% of the adrenal weight is the cortex. the cortex contains steroidogenic cells which produce steroid hormones, in these cells are fat droplets, cholesterol many mitochondria to rapidly produce hormones on demand. the cortex is derived from mesodermal tissues the medulla tissues derives from neural tissue, it is underdeveloped neural tissue. they have the potential to be neurones but the bathing of the cortex prevents them differentiating.

Phosphatidylethanolamine

one of the most common phospholipids

oogenesis

oocytes are formed in the develpoing ovary, they arrest in prophase on meiosis divison 1 and exist within primordial follicles wich contains the oocyte surrounded by a layer of follicular cells, these develop from the stroma. at birth there is around 7 million potential eggs but most die before puberty, at menarche around 300,000 remain but more die by atresia and only around 30,000 develop further but most of them will down and only 500 eggs are released by ovulation.

acetylcholine as the neurotransmitter

opens Na+ ion channels in the post synaptic membrane, these are also permeable to K+ ions and they diffuse out of the cell. the post synaptic membrane reaches -15 mV (not the threshold) this is the end plate potential. acetylcholine is broken down by acetylcholinesterase to produce choline and acetate which can diffuse back into the presynaptic membrane

mitochondria function

oxidative phosphorylation, FeS cluster biosynthesis (needed in every cell to sruvive)

posterior pituitary hormones - hormones produces in the magnocellular neurones of the hyopthalamus and are stored in the posterir pituitary prior to release

oxytocin -> uterine smooth muscle contraction (important during labor) and breat myoepithelia contration (promotes lactation). a stimuli for hormone release is suckling. antidiuretic hormone (ADH) -> water retention by the kidney

the pKa and the Henderson Hasselbach equation tells us the state of a molecule at a given pH

pH < pKa mainly in weak acid form pH > pKa mainly in conjugate base form pH = pKa half dissociated

Henderson-Hasselbalch equation this equation descirbes how pH varies in a buffer

pH = pKa + log [A-]/[HA] derived from the acid dissociation equation

pKa = -log10(Ka) tells us the ratio of products to reactant

pKa tells us how strong as acid is if it is: - < 3 it is a strong acid 3 < - < 7 it is a weak acid 7 < - < 11 it is a weak base - > 11 it is a strong base

passive transport active transport

passive - diffusion, facilitated diffusion active - primary active transport is where the same protein generates the energy needed to transport the molecule, secondary active transport is where a concentration gradient is set up by a primary transporter

Endomembranes

phospholipid membranes with embedded proteins that are quite similar to the cell membrane but occur within the cytoplasm, they are involved in transport within the cell and allow separate compartments to have different constituents and functions. they are organelles

chloroplasts function

photosynthesis

thyroid stimulating hormone will: - increase iodine uptake - increase thyroglobulin synthesis - increase iodination of thyroglobulin - increases pinocytosis of colloid - increase lysosomal activity - increase in size of thyroid cells

pinocytosis - the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane (cooloid into the follicular cell)

pituitary gland aka the hypophysis has two lobes; the anterior and posterior

posterior pituitary -> the posterior lobe is of neutral origin and is known as the neuropophysis, it consists of axons and nerve endings of neurones whose cell bodies reside in the hypothalamus. anterior pituitary - lobe originates from Rathke's pouch (endocrine origin) and is known as the adenohypophysis, it consists of endorcrine tissue

hydrophobicity plot

predicts location of transmembrane domains in proteins. the segement of the protein typically embedded in the lipid layer is made up of hydrophobic amino acids which have different chemical and physical properties, amino acids in the positive hydropathy index are associated with the membrane (embedded). more positive hydropathy index value = more hydrophobic amino acid

gametogeneis

production of gametes for sexual reproduction; spermatogenesis and oogenesis both controlled by FSH and LH but effects are different

apoptosis

programmed cell death, it can be signaled during any phase of mitosis. cells shrink in on themselves as if they exploded then harmful material could be released into the cells environment, there is nuclear condensation and fragmentation. the membrane changes trigger phagocytosis and so the apoptotic bodies will be recycled. physiologic activation - apoptosis is triggered during embryonic activation to remove or remodel tissues pathogenic activation - viral infection, heat shock, toxins to remove stressed or damaged cells. it is regulated by external signals and activated by hormonal signals or direct from the contacting cell and suppressed by survival factors.

sensory neurone structure

pseudo-unipolar - one process from the cell body which splits into two bipolar - two processes from the cell body sensory neurones can be either

order of a reaction

rate = k[A]^x * [B]^y x,y are orders of reaction with respect to A, B respectively not all substances that appear in the reaction equation appear in the rate equation as not all effect the rate overall order of reaction is x + y

rate of reaction

rate of change of the amount of product or reactant with time units - M/s rate depends of reaction stoichiometry which is used to determine to amount of product or reactant to be produced or needed in a reaction - their quantitative relationship.

how reactions at equilibrium react to a deviation in the system (Le Chateliers principle)

reaction is pushed out of equilibrium, the free energy of the system has been pushed away form the minimum free energy of the system - to reverse this either more product is formed or broken down.

intracellular receptors

receptors located inside the cell rather than on its cell membrane, small hydrophobic signalling molecules can cross the membrane by binding to the receptor examples: -nuclear hormone - confromational change in response to ligand binding which leads to transcription of target genes -nitric oxide receptors - acetylcholine diffusing into the cell causes NO synthesis, NO molecules bind to receptor which then undergoes a conformational change and triggers a secondary messenger response

endoplasmic reticulum function

rough - formation and modification of proteins smooth - formation of lipids

the golgi apparatus

sacs of membrane called cisternae. it polar so there in an inner cis face where vesicles enter and an outer trans face where vesicles are exported

determining solubility

small ionic compounds usually dissolve by simple charge-charge interactions large molecules dissolve depending on their side chains - more polar/ charged functional groups = more soluble

state of a substance vs microstates

solid - particles fixed so few translational mircostates liquid - particles can move more freely so more positional microstates gas - even more positional microstates entropy increases from solid to liquid to gas as more positional configurations can be accessed. as kinetic energy of a system drops the number of accessible microstates drops, kinetic energy and temperature are ionterchangeable.

endosomes function

sorting of internalised material, reversed exocytosis so taking material into the cell from the plasma membrane

spatial and temporal summation

spatial - multiple subthreshold EPSPs arrive at the trigger zone (from different loactions in the neurone) at the same time and sum to create a suprathreshold signal temportal - summation of graded potentials can also occur from one presynaptic neurone if the graded potentials arrive at the trigger zone close enough together in time

Eukaryogenesis

stage one - aquisition of the nucleus and the ER membrane stage two - aquisition of the mitochondria (alpha-proteobacteria ingested by the cell where it then had a dual beneficial relationship with the cell and overtime evolved into modern mitochondria)

Aldosterone vs. Cortisol

structurally similar so can have a small effect on each others receptors but the effect is much much less. there is around x100 more cortisol so cortisol can stimulate mineralocorticoid and swap any effect caused by changing aldosterone conc. to stop this occuring there is an enzyme called 11 beta-hydroxysteroid dehydrogenase is aldosterone responsive cells which converts cortisol into an inactive form to allow aldosterone to have the main effect on its receptors.

cushing's syndrome cuases by hypersecretion of cortisol, commonly the result of glucocorticoid therapy but spontaneous syndromes caused by pituitary or adrenal gland abnormalities. cushing's disease is specifically cushings syndrome but when cuases by a pituitary tumour

symptoms: - weight gain - moon face - atrophy of epidermis - hypertension - psychological disturbances - muscle weakness -osteoporosis -thirst & polyuria (due to inhibition of AHD secretion)

synaptic plasticity

synapses are not fixed and variation in electrical activity can cause rearrangements of the circuit connections, this means synaptic transmission at a given synapse can change in repsonse to sensory input from things like past experiences. this allows us to learn and have memory

classes of hormone: steroid

synthesised by a modification of cholesterol, they are made on demand and are not stored inside the cell. - they are small hydrophobic molecules synthesised primarily from cholesterol - they are released immediately following synthesis - they are bound to a protein due to their hydrophobic form - they act on intracellular receptors which then bind to DNA and regulate gene transcription - have slow long lasting effects as it takes time to make new proteins and protein expression depends on rate of production and the half-life of the protein which limits the speed and longevity of the effect (half-life to do with protein degradation)

feedback control: complex feedback

system hypothalamus -> releases factors (neurohormones) factors -> act on the anterior pituitary wihch is an endocrine glad anterior pituitary -> releases trophic hormone trophic hormones -> act on specific sites on endocrine tissue endocrine tissue -> release a hormone hormone -> has systematic effects -hormonal feedback -the tropic hormone can feedback to the hypothalamus and, depending on the concentration, stop or reduce production of the releasing factors - homronal - the hormone produced by the endocrine tissue can feedback to the anterior pituitary and thr hypothalamus so they recognise that the hormone levels have risen to reduce production - sensory - the effect caused by the hormone can feedback to the hypothalamus and other brain area inputs which detect changes in the body.

time for something to diffuse across the cell

t = R^2/6D t = time scale R = traverse distance D = given diffusion coefficient diffusion is efficient over bacterial distance scales but not over eukaryotic distance scales because the traverse distance is very large - this is which eukaryotes need molecular motors.

the luteal phase of ovarian cycle

takes 12-15 days. the corpus luteum develops over ~14 days, after the egg has ruptured. the granulosa cells fill with lipid. the major product of the corpus luteum is prgesterone which goes on the help the development of the embryo. oestrogen levels decrease due to LH surge but then begin to rise again, if there is no pregnanct the corpus lutemu degenerates into corpus albicans and oestrogen and progesterone levels fall allowing FSH and LH levels to rise . if a pregnancy, the corpus luteum produces progesterone to keep the embryo alive. the placenta produces chorionic gonadotrophin which enables the corpus luteum to persist. eventually corpus luteum diminishes into scar tissue.

gonads in the male are testes and in female are the ovaries, involved in gametogenesis and sex hormone production (steroid).

testes: secrete large amounts of androgens and small amounts of oestrogens ovaries: secrete large amounts of oestrogens and small amounts of androgens secrete profesterone which prepares the utures for pregnancy

temperature

the ability of one body in contact with another body to transfer heat or on a molecular level the vibrations of particles.

apical/ basal side/ tight junction

the apical and basal side of the cell are two different compartments separated by a tight junction. the tight junction is a combination of protein and lipid which creates a tight connection between the cells and the membrane, this is essential to maintain polarity in the cells e.g to transfer a metabolite unidirectionally.

plasma

the blood with all the cells removed

internal energy, U, what is it? how is it stored in a system?

the capacity of a system to do work it is stored as: - chemical potential within molecules in chemical bonds or between molecules e.g hydrogen bonds - as motion ie kinetic energy

Brownian motion

the chaotic movement of colloidal particles, caused by collision with particles of the solvent in which they are dispersed. smaller particles collide less often than larger particles so they move faster but the movement is always random due to the collisions. molecules in solution move due to thermal energy. small particles have a loner mean free path than large molecules.

Laws of Thermodynamics: Second Law

the entropy, S, of an isolated system will increase or remain the same. entropy/disorder always increases entropy measures how disordered a system is. the second law means that the entropy of the universe will increase or remain the same and this defines the arrow of time - the future is the direction in which things get messier.

haematoxylin and eosin stain of thyroid gland

the functional units of the thyroid are the follicles which are the little pink cells in the diagram a single layer of these cells surrounds each pool of colloid (the large opaque areas). the colloid is where we produce and store thyroid hormones. the follicular cells are important in production. we can store up to 3 months of thyroid hormone in the gland. the amount of colloid varies; more where the thyroid is inactive and little when someone is iodine deficient. in an unstimulated state the follicular cells are cuboidal and become more columnar when active. cells secrete calcitonin which are involved in calcium homeostasis, the c cells reside in the connective tissue.

action on receptors: steroid hormones

the hormone receptor has different regions: - the hormone binding site - the DNA binding domain - transcription activating domain - inhibitory protein complex (bound in the inactive state) - it hides the DNA binding site when the hormone binds to the receptors the hinge region opens up and exposes the DNA binding site when the inhibitory protein complex detaches

Structure of hypothalamus and pituitary gland

the hypothalamus is part of the brain and the pituitary dangles down. anterior and posterior lobes make up the pituitary and both originate from different tissues and have different functions. pituitary can shrink or expand e.g expands during preganayc due to larger amount of hormones produced. hypothalamus. posterior pituitary: up into the hypothalamus are the paraventricular nuclei and the supraoptic nuclei which is where the hormones are produced (within the cell bodies), these nuclei are joined to the posterior pituitary via magnocellular neurones which extend through th supraoptic hypothalamic tract. the hormones are packaged, sorted and stored in the posterior pituitary. hypothalamus/ anterior pituitary: in the hypothalamus there are parvocellular neurones which release factors (neurohormones) which drain their contents into a blood supply, a series or capillaries, this is what connects the hypothalamus and the pituitary. the releasing factors travel through hypophyseal portal vessels into the anterior pituitary and from there the releasing factors act on the endrocrine cells which make up the anterior pituitary and trigger the release of hormones. hormones released by these endocrine cells enter the body and act on any cells with the specific receptor.

diffusion definition

the net influx of molecules down a concentration gradient die to random thermal motion flux = permeability * ([C]1 - [C]2) at steady state where [C]1 is high conc and [C]2 is low conc

Archezoa hypothesis

the nucleus was invented before mitochondriom therefore the first eukaryotes were anaerobes (as no site for aerobic respiration). Archezoans are a branch of eukaryotes that derived before the formation of mitochondria

absolute refractory period

the period immediately following the firing of a nerve fiber when it cannot be stimulated no matter how great a stimulus is applied. Na+ ion channels are inactive

formation of a primary plastid

the result of a cell taking up a photosynthetic bacterium, called cyanobacteria, this is believed to have occured much later than the formation of the nucleus and mitochondria

axon initial segment

the segment of the axon where action potentials are generated - located immediately adjacent to the axon hillock. a tight junction-like structure in cells which contain an axon which ensures that membranal proteins from the main body of the cell don't diffuse along the axon

transport into the RER

the signal sequence is on the N-termial on the protein, the signal binds to a receptor on the RER and the ribosome synthesising the polypeptide chsain associates with the RER, protein synthesis is completed and the signal is then cleaved. most proteins in the RER are glycosylated - N-glycosylation (sugar added to nitrogen) or O-glycosylation (sugar added to oxygen)

hormone activation

there are some post release modifications that activate hormones e.g vitamin D must be activated in the kidney angiotensinogen -> angiotensin II

cyclin-dependent (Cdk)

these are enzymes which add a phosphate group from ATP to an amino acid in a protein and this phosphorylation sends a signal to the cell to say that the cell is ready to proceed to the next step in the cell cycle. the cyclins are destroyed as the cycle advances so their concentrations change throughout. growth factors bind to a receptor on the surface of the cell which stimulates the release of P1 kinase which eventually causes stimulation of cell growth.

motile cilia

they are moved by dynesins, they have a 9+2 microtubule arrangement, dyneins cause the structure to bend making the cilia move

rate limiting step

this determines the rate of the reaction biological example: michaelis-menten enzyme kinetics where the rate limitng step is the formation or the intermediate step where the enzyme and substrate are bound E + S <=> ES <=> E + P

signal => reception => transduction => amplification => response

transduction = conversion of one type of signal to another amplification = increase the magnitude of the signal

together the hypothalamus and the pituitary make up the hypothalamic-pituitary axis or the hypothalamohypophyseal system

this is the major site of interaction between the nervous and endrocrine systems, it exerts control over several endocrine glands and a number of physiological activites

different types of endocrine cell and their major function

throtrophs -> control the function of the thyroids gonadotrophs -> control the function of the gonads corticotrophs -> control the release of hormones which control adrenal glands somatotrophs (most abundant) -> control growth hormone production lactotrophs -> control the production of prolactin

thyroid homrones are produced by iodination and coupling of tyrosine (they are examples of amino acid hormones).

thyroglobulin is invovled in the hormone production. this glycoprotein is synthesised by follicular cells and released into the follicular lumen by exocytosis, at the apical follicylar membrane-colloid boarder, tyrosine residues within thyroglobulin are iodinated in the presence of the enzyme thyroperoxidase. on the way to making T3 and T4 you make precursors which are monoidotyrosine (T1) and diidotyrosine (T2) which have no physiological effect but they can be coupled to form T3 and T4 which do, under the control of thyroperoxidase.

hypothalamic hormones -> releasedhypothalamic hypophysiotropic hormones into the portal circulation and act upon the anterior pituitary stimualtes the release of releasing factors

thyrotropin-releasing hormone (TRH) - stimulates TSH (thyroid stimulating hormone) and prolactin release gonadotrophin-releasing hormone (GnRH) - stimulates FSH (follicle stimulating hormone) and LH (luteinizing hormone) release corticotrophine-releasing hormone (CRH) -stimulates ACTH (adrenoacorticotropic hormone) and prolactin release growth hormone-releasing hormone (GHRH) - stimulates GH (growth hormone) release growth hormone-release - inhibiting hormone (somatostatin) - inhibition of GH release, also of gastrin, VIP, glucagon and insulin dopamine - inhibits prolactin release

protein transport - transmembrane

transport across membranes, between the cytosol and plastids, mitochondira, perioxisomes and the endoplasmic reticulum

protein transport - vesicular

transport by vesicles, between the golgi body and endosomes, lysosomes, secretory vesicles, the cell exterior and endoplasmic reticulum. it is also between ER and peroxisomes, endosomes and lysosomes, the secretor vesicles and the cell exterior.

signal sequences are used to transport proteins around the cell, they are usually part of the amino acid sequence of the protein.

transport in the mitochondria or ER have a signal sequence at the N-terminal which whereas transport into the nuclear occurs when the protein is tagged with a nuclear localisation signal. for transport into peroxisomes the signal must be at the end of the amino acid sequence

protein transport - gated

transport through nuclear pores, between the cytosol and the nucleus

trimeric G-protein vs monomeric G-protein

trimeric - bind directly to the receptor, the receptor activates GDP release, GTP hydrolysis by GTPase activity in alpha subunit monomeric - not directly linked to the receptor, GDP release is activated by GEF, weak GTPase so needed GTPase activating protein (GAP) to drive GTP hydrolysis

T-tubules/Sarcoplasmic Reticulum

tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side. they carry the action potential deep into the muscle fibre, right next to each myofibril. the sarcoplasmic reticulum surround the myofibrils and enlarge into the terminal cisternae near the T-tubules, the temrinal cisternae stores Ca2+ ions which are release when an action potential arrives

transport into mitochondria and chloroplasts

two membranes must be crossed; TOM is outer, TIM is inner. the protein is made outside of the cell and has a specific signal sequence on the end which is recognised by a receptor protein in the TOM complex, the protein moves through the TOM complex and the TIM complex at the same time into the cell where the signal sequence is cleaved and the protein is refolded. some proteins that are transported into the cell become embedded in the membrane, the way this occurs in mitochondria is very similar in bacteria and so is evidence of the bacterial origin of mitochondria.

graded potential

variable-strength signals that travel over short distances and lose strength as they travel through the cell. they combine to trigger action potentials. they occur in: - dendrites - cell body - axon terminals the further from the OG Na+ ion channel the potential is the weaker it is. they can be depolarising or hyperpolarising. they only trigger an action potential if they are strong enough when they reach the axon hillock.

storage of thyroid hormones

we can store up the thyroid hormones bound to thyroglobulin inside the colloid.

laws of thermdynamics: 3rd law

when the entropy of a system is zero the system is at zero temperature

follicular phase of ovarian cycle

~ 28 days duration of ovarian cycle 3 phases of egg maturation: follicular phase (several months)- maturation of primary follicules. 1/ pre-antral phase- primordial follicle -> primary follicle where the follicular cells become cuboidal and a zona pellucida which have a particular sensitivity due to specific proteins. this process is supported by paracrine factors which stimulate growth, antimullerian hormone is what limits the number developing at the same time. primary follicle -> mature pre-antral follicule as the zona granulose cells multiple and stimulate the stroma to develop into thecal cells as the cells develop they support the devleopmemnt od the surrounding cells so the egg all matures at the same rate 2/ antral phase - the appearance of flui filled atria, increaed layers of zona granulose, thicket zona pellucida and the theca interna is more apparent. this growth is dependent on FSH (anterior pituitary hormone). theca interna cells start producing androgens and glomerulosa cells reposnd to FSH and begin to grown and procude aromatase which converts androgens to oestrogen. as oestrogen levels rise, FSH levels drop. this produces a dominant follicle as when the FSH levels drop only the strongest follicle will be able to cope. #theca cells catalyse androgen production from cholesterol. Granulose cells contain aromatase so they can convert the androgen to oestrogen. 3/ pre-ovulatory phase - corona radiate forms around the oocyte, very large antrum. one large Graafian follicle which repsonds to a surge in LH which completes the first meiotic division and arrests it in metaphase of meiosis II. this forms a haploid scondary oocyte and a polar body. there is then an increase in FSH conc which increases LH receptors and enzyme expression in granulose cells - causes progesterone production. inflammatory cytokines and hydrolytic enzymes are released by the theca and granulose cells, these eat away at the follicular wall and that of the ovary (causes a rupture) so a hole is formed in the ovary to allow the free egg with its associated zona pellucida and corona radiata (crucial for capture) to be released into the peritoneal cavity. it is captured by the fimbriae. the remnants of the follicle in the ovary go on to fomr the corpus luteum

sarcomere structure

•Z-lines: define the boundaries of each sarcomere •M-line: located in the middle of the sarcomere •I-band: contains only thin filaments •H-zone: consists of only thick filaments •A-band: contains the thick filaments in their entirety thick filaments - myosin, head and tail structure, several 100s of myosin molecules make up each filament thin filaments - made of G-actin, troponin and tropomyosin. G-actin molecules for a strand, two of these wind together in a double helix and a filament of tropomyosin then winds around the helix, troponin molecules bind to both actin and tropomyosin.