Physiology (Bio 206) Unit 2 Exam

Gene

"transcription unit" a region of DNA that contains the information needed to make a functional protein one DNA molecule is made up of many genes each contains the "instructions" for one or more specific proteins

SUMMARY STEPS OF THE CELL CYCLE

1) INTERPHASE (aka G0 phase): G1 phase S phase G2 phase 2) MITOSIS: prophase metaphase anaphase telophase 3) CYTOKINESIS

What are the 4 categories of extracellular signal receptor molecules?

1) RECEPTOR CHANNEL: binding of a ligand opens or closes the channel and changes the flow of ions across the membrane 2) G PROTEIN-COUPLED RECEPTOR: has 7 membrane-spanning regions. when it binds its signal molecule, it will open an ion channel or alter the activity of intracellular enzymes (ex: adenylyl cyclase) TWO KINDS OF CATALYTIC RECEPTORS: 3) RECEPTOR-ENZYMES: when it binds its signal molecule, an intracellular enzyme that is physically attached to the receptor is activated 4) INTEGRIN PROTEINS: binding of a signal molecule to its receptor leads to a change in the intracellular cytoskeleton or enzymes

Steps of Transcription:

1) Regulatory Proteins (aka Transcription Factors) come in and bind to a region up-stream of the actual gene, in an area called the "promoter." this creates a landing pad for the RNA polymerase to bind at the beginning of the gene. this stimulates RNA polymerase to bind 2) RNA polymerase binds to DNA at the beginning of the gene based on where the promoter said to bind 3) the section of DNA that contains the gene unwinds/ un-zips 4) RNA binds to DNA, creating a single strand of pre-mRNA and is read as a template. RNA bases are added in a complementary way, read the DNA genetic code, and insert the complementary RNA nucleotides (starting to make an mRNA copy) 5) once the end of the gene is reached, pre-mRNA and the RNA polymerase unbind/ dissociates/ detaches from DNA, and the pre-mRNA goes to the cytoplasm after processing

The 4 Steps of Gene Expression

1) Transcription: happens in the nucleus. make a copy of a specific gene on the DNA (DNA is located in the nucleus and cannot leave). this copy of a gene is a nucleic acid molecule called "pre-messenger RNA (pre-mRNA)" 2) mRNA Processing: happens in the nucleus. original mRNA molecule "trimmed" or "edited" to make one or more mature mRNA molecules, which can then leave the nucleus and convey their information to the first ribosome they run into in the cytosol 3) Translation: happens at the ribosome in cytosol or on rough ER). at a ribosome, mRNA is "read" as instructions for building a protein one amino acid at a time. amino acids are assembled into a specific sequence forming a peptide chain according to nucleotide sequence encoded on mRNA transcript. 4) Post-Translational Modification: optional step. happens within the lumen of the rough ER for only some proteins. some proteins need additional chemical modifications or assembly with other tertiary subunits before they are ready to begin their work. (ONLY SOME NEED THIS STEP)

To up-regulate the amount of protein available to do work a cell must:

1) access the specific gene (subsection of one DNA molecule) in the nucleus (that gene is the "recipe" for making 1 or more proteins 2) make an RNA copy of the gene (transcription) 3) sometimes, make selective edits to the RNA copy of the gene (might be split, recombined, or fine-tuned) 4) bring that RNA copy to a protein assembly site (the ribosomes located in the cytoplasm) 5) "read" the recipe encoded in the RNA copy and build the polypeptide/ protein (translation) 6) some proteins must also undergo additional post-translational modification (occurs in the rough ER) before they are ready to do their programmed job

Summary 3 Stages of Translation

1) initiation 2) elongation 3) termination

What are the 4 steps of how carrier proteins work?

1) one side of the plasma membrane is open 2) the substrate binds: the binding sire has high affinity (attraction) in this initial configuration 3) carrier protein changes shape when substrate is bound: this conformational change opens a passageway to the other side 4) substrate releases: the binding site switched to low affinity in this new configuration GATE IS NOW CLOSED

Cyclic AMP (cAMP)

A compound formed from ATP that acts as a second messenger in the adenylyl cyclase pathway

Transport across membranes concept map

Active Transport: 1) vesicular transport (ATP) exocytosis endocytosis phagocytosis 2) protein mediated direct or primary active transport (ATP) indirect or secondary active transport (concentration gradient created by ATP Passive Transport: 1) simple diffusion (concentration gradient) 2) protein mediated facilitated diffusion ion channel (electrochemical gradient) aquaporin channel (osmosis)

protein phosphatases

An enzyme that removes phosphate groups from proteins, often functioning to reverse the effect of a protein kinase

How do pancreatic beta cells know to release insulin instead of beta cells?

BETA CELL AT REST: in-between meals resting membrane potential = -70mV 1) low blood glucose levels 2) metabolism slows 3) ATP decreases (due to low glucose concentration) 4) KATP channels open and K+ ions leak out of the cell (ATP-gated K+ channel) (no ATP to bind to so K+ can leak out) 5) the cell is at resting membrane potential, so no insulin is released (stays inside secretory vesicles) (voltage-gated Ca2+ ion channels are closed, so no insulin is released) BETA CELL SECRETES INSULIN: when you eat a meal 1) high blood glucose levels (from eating a meal with all macromolecule categories). glucose diffuses into beta cell with help from GLUT transporter 2) metabolism increases (due to stimulation from glycolysis and the citric acid cycle) 3) ATP production increases (due to increase in glucose from meal) 4) KATP channels close (due to ATP binding to the KATP channel) 5) cell depolarizes (become more positive due to the retention of K+ ions in the cell), which then causes the calcium channels to open 6) Ca2+ ions enter from the ECF (moving down their electrochemical gradient), which act as an intracellular signal 7) Ca2+ ion signal triggers exocytosis of the insulin-containing vesicles, and insulin is secreted into the ECF

What types of proteins are subtypes of membrane transporters that are used for facilitated diffusion?

CHANNEL PROTEINS: voltage-gated, chemically-gated, mechanically-gated CARRIER PROTEINS: uniport carriers, symport carries, antiport carriers

Chromatin vs. Chromatid

CHROMATIN: the state of DNA when it is loosely bound/ diffused around histone proteins open for business phase after DNA is replicated in S phase, all loose DNA molecules begin to condense by wrapping around histone proteins to form chromatin it is the state of the DNA after cell division is completed and the daughter cells begin to synthesize new proteins to maintain homeostasis CHROMATID: when chromatin further condenses into a "log-like" structure all of it is organized and condensed one line of the two lined chromosome they form after DNA replication completes, just before mitosis begins can be seen with a light microscope

Changes in Membrane Potential (Depolarization, Repolarization, and Hyperpolarization)

DEPOLARIZATION: (less polarized/ more +) cells become more positive inside, compared with resting potential the difference between the inside and the outside is reduced to activate a cell, it must be depolarized example = if Na+ ions were to diffuse through an ion channel, the inside of the cell would become more positively charged (depolarized) REPOLARIZATION: (polarize again) returning from depolarized state towards resting membrane potential "resting state" example = if Cl- ions move through an ion channel and then quickly the Na+ channels closed, and the K+ channels opened, the inside of the cell would return to its resting state (become repolarized) HYPERPOLARIZATION: (more polarized/ more -) becoming more negative inside the cell, when compared with the resting membrane potential must be polarized to prevent a cell from being activated example = if Cl- ions move through an ion channel, the inside of the cell would become hyperpolarized, meaning it became more negative

Diploid vs. Haploid

DIPLOID: when a cell has two copies of each gene HAPLOID: when a cell as one copy of each gene DI = 2 HA = 1

What forms can physiological signals take?

ELECTRICAL SIGNALS: changes in cell's membrane potential due to the differences in ion concentrations inside vs outside the cell CHEMICAL SIGNALS: molecules secreted by cells into the ECF (exocytosis) and attached by specialized receptors elsewhere in the body both of these signals are responsible for most of the communication within the body

Glucose Transporter Carrier Proteins Example

GLUT-2s or GLUT-4s there is a high concentration outside of the cell due to blood delivery of glucose there is a low concentration inside due to cell metabolism glucose becomes G-6-P immediately, so glucose is always in low concentrations inside cells, meaning glucose always wants to move through cells glucose cannot pass through the lipid bilayer on its own, so carrier proteins are needed to facilitate their movement into the cell > glycogen low [glucose] >>>>>>> G-6-P ATP > ADP > glycolysis

Rules for diffusion of uncharged molecules

General Properties of Diffusion: 1) diffusion uses kinetic energy of molecular movement and does not require an outside energy source 2) molecules diffuse from an area of higher concentration to an area of lower concentration 3) diffusion continues until concentrations come to equilibrium. molecular movement continues, however, after equilibrium has been reached. 4) diffusion is faster... along higher concentration gradients over shorter distances at higher temperatures for smaller molecules 5) diffusion can take place in an open system or across a partition that separates two systems Simple Diffusion Across a Membrane: 6) the rate of diffusion through a membrane is faster if... the membrane's surface area is larger the membrane is thinner the concentration gradient is larger the membrane is more permeable to the molecule 7) membrane permeability to a molecule depends on... the molecules lipid solubility the molecules size the lipid composition of the membrane

How does the ratio of body water volume differ between intracellular fluid and extracellular fluid?

ICF = 2/3 of total body water volume ECF = 1/3 of total body water volume

Compare the levels of disequilibrium in ICF vs. ECF

ICF: fluid inside cells low [Na+] high [K+] low [Cl-] low [HCO3-] high [proteins] ECF: fluid outside (around) of the cell Interstitial fluid: fluid that lies between he circulatory system and cells high [Na+] low [K+] high [Cl-] low [HCO3-] no proteins Plasma: the liquid matrix of blood high [Na+] low [K+] high [Cl-] low [HCO3-] high/med [proteins] given the distribution of ions and their charges, the ICF compartment has a more negative charge relative to the ECF compartment this sets up a polarity/ separation of charge at the plasma membrane, which is called MEMBRANE POTENTIAL

Inositol Triphosphate

IP3 in the phospholipase C pathway, there are several second messengers, but this is the one that ultimately releases Ca2+ ions from intracellular stores A second messenger that functions as an intermediate between certain nonsteroid hormones and a third messenger, a rise in cytoplasmic Ca 2+ concentration.

What are the methods of local cell-to-cell signaling? What are the methods of long-distance cell-to-cell signaling?

Local Signaling: gap junctions contact-dependent signals autocrine signals paracrine signals Long-Distance Signaling: hormones cytokines neurotransmitters neuromodulators neurohormones

Mitosis vs. Meiosis

Mitosis: one somatic cell division forming 2 identical daughter cells (clones) that are identical to the parent cell Meiosis: two divisions forming 4 daughter cells that are genetically different bc they have one copy of each chromosome

Locations For Protein Synthesis:

NUCLEUS: where the process of copying a section of DNA into RNA occurs in the cell RIBOSOMES: the intracellular inclusions where the process of reading the RNA and actually assembling the new protein happens ROUGH ER: in the lumen of the rER is where the ribosomes will direct their protein into the rER so post-translational modification of proteins can occur

Open vs Gated Channels

OPEN CHANNELS: pores that spend most of their time with their gates open, allowing free flow of ions to move back and forth across the membrane without regulation (via facilitated diffusion) aka "leak channels" or "pores" specialized water channels are made from proteins called AQUAPORINS GATED CHANNELS: spend most of their time closed, which allows them to regulate the movement of ions across the plasma membrane they need a trigger to open or close them necessary to regulate or control movement of ions into or out of the cell based on the needs at any given moment voltage-gated, chemically-gated, mechanically gated when they are opened, only specific ions pass through, and they do do via facilitated diffusion

Saturation and Protein-Mediated Transport

Principle of Saturation = when all binding sites are occupied and the rate of work can no longer increase, the protein is considered saturated increasing concentration/ amount of protein can up-regulate (which is done via protein synthesis) the more substrate, the more activity of the protein, but only until its maximum level of saturation is reached Saturation and Protein-Mediated Transport: channel proteins and carrier proteins are similar to enzymes because they have binding sites and change shape if the concentration of their substrate increases, so will their rate of work, but only until the "transport maximum" is reached (represent their point of saturation)

How does a cell make new proteins?

Protein Synthesis DNA is the molecular "cookbook" for creating all proteins needed to maintain homeostasis a cookbook with 46 different chapters, but actually more like 23 pairs of chapters each chromosome is a distinct molecule of 1 DNA molecule

Transcription Factors

Regulatory proteins that bind to DNA at the promoter region and either activate or inactivate the expression of a gene need energy to work

What happens after the signal molecule binds to its receptor?

SIGNAL TRANSDUCTION: membrane proteins that transmit information from one side of the membrane to the other it converts one form of a signal into another STEPS OF SIGNAL TRANSDUCTION: begins in ECF 1) signal molecule (1st messenger) binds to... 2) membrane receptor protein (transducer) which initiates/ activates... 3) intracellular signal molecules (second messenger system) which alter... 4) target proteins (the targets) that create a.... 5) response

Muscle Cell Signal Pathway Example

STEPS (in a process map-like fashion): 1) a SIGNAL MOLECULE released by somatic motor neurons (neurotransmitter = acetylcholine (ACh)) binds to... 2) a RECEPTOR PROTEIN on the target cell membrane (ACh receptor on muscle cell, it does not enter the cell) activates... (the muscle cell is stimulated to do something) 3) an INTRACELLULAR SIGNAL MOLECULE chemical messenger is spread inside the muscle cell after.... 4) the TARGET PROTEINS, actin and myosin, do their job which creates... 5) a final RESPONSE, in this case is the muscle cell contracting

Types of Gated Channels

VOLTAGE-GATED CHANNELS: these channels will open when the electrical state of the cell reaches a specific level they open to a response in the cell's membrane potential CHEMICALLY GATED-CHANNELS: these channels must bind an ICF or ECF signally molecule/ chemical stimulus to become open (ex: ligand bind to receptor MECHANICALLY-GATED CHANNELS: these channels open in response to pressure or temperature changes

Can water move freely through the cell membrane?

YES, for the most part some body cella re actually water-tight usually water moves freely through the membrane or through specialized water channels called AQUAPORINS therefor osmotic equilibrium can be maintained

Chromosomes

a general term that can be used in two different ways: 1) to describe the visible "x-shape," which is two sister-chromatids attached together 2) to describe a specific DNA molecule regardless of its shape the state when pieces of chromatin condense again, they can actually be seen with a light microscope human cells contain 23 pairs of homologous chromosomes, one inherited from each parent cells always have chromosomes, but they are not always condensed the two homologous chromosomes (C1 from mom, C1 from dad) contain genes that code for the same characteristics, but each inherited pair of genes can be slightly different (called ALLELES, which are genes that code for variation in things like eye and hair color) only a gene on one homologue is expressed (the dominant allele/ gene) the same allele on the other homologue is not expressed (the recessive allele/ gene) exceptions in alleles = co-dominance, which is where a person can express both the A and B proteins on erythrocytes

Neurohormone

a method of long-distance cell-to-cell communication much slower than neurotransmitters and neuromodulators neuro = from neuron hormone = chemical released into the blood a neuron that secretes a signal molecule into the blood stream for distribution they bind to target cells with specific receptors and change their function in specific ways

Neurotransmitters (NT)

a method of long-distance cell-to-cell communication when a neuron secretes a signal molecule that binds to specific receptors in a nearby neuron with rapid/ short-term effects on the target cells function they cross synapses to target cell that is only a few nanometers away released from an axon terminal into synaptic cleft act much quicker than hormones

Neuromodulator (NM)

a method of long-distance cell-to-cell communication when a neuron secretes a signal molecule that binds to specific receptors in a nearby neuron with slow or prolonged effects on the target cells function they cross synapses to target cell that is only a few nanometers away released from an axon terminal into synaptic cleft act much quicker than hormones

Hormones

a method of long-distance cell-to-cell communication a chemical signal that is secreted by endocrine gland or specialized cells into the blood and then is distributed all over the body by circulation to distant target cells the target cell it is signaling to has a specific receptor for the hormone it is trying to reach these signals may time some time to reach the target cell, so they typically mediate slow changes in body functions neurotransmitters and neuromodulators act much quicker than hormones

Cytokines

a method of long-distance cell-to-cell communication they can be produced by almost every cell in the body, and are particularly important in immune system functions they are similar to hormones expect that they are made on demand (not stored in vesicles like hormones are) and they are not released by specialized cells (they can be produced in and secreted from any nucleated cell in the body)

Transfer RNA (tRNA) and its role in TRANSLATION

a specific kind of RNA that brings its attached amino acid to the ribosome during protein synthesis, and drops off so it can be attached to the growing polypeptide tRNA acts as the "translator" between mRNA and the growing amino acid sequence tRNA brings the ribosomes the needed amino acids when that ribosome is reading a particular codon t = transfer and because tRNA is shaped like the letter "t" tRNA has a specific ANTICODON on one end and carries the corresponding amino acid on the other end ANTICODON: a triplet of bases that binds to a complementary codon triplet on the piece of RNA that was created from the DNA template there are 20 distinct tRNA molecules, each carrying a specific amino acid to ribosomes as the ribosome "reads" each mRNA codon, it only allows the tRNA with a complementary anticodon to deliver its specific amino acid to the growing polypeptide (ex: if mRNA codon = CGA, then the tRNA anticodon = CGU and this tRNA carries the amino acid argenine) the ribosome will then link the amino acids with new peptide bonds to continue the growing peptide chain, which is in its primary sequence/ structure (what defines all other levels of structure)

mRNA (messenger RNA)

a specific kind of RNA that is complementary to a gene coded in DNA and is ultimately read by ribosomes to create the protein the form of RNA which is created as a blueprint from DNA; carries instructions for making a protein it is similar to DNA, but made from nucleotides that contain the pentose sugar molecule RIBOSE (not deoxyribose) it is a single-stranded nucleic acid URACIL replaces THYMINE and is paired with ADENINE it may have been the precursor to DNA. it is not quite as stable as DNA. it can fold into 3D structures like proteins through complementary, base-pairing rules. it can act as an enzyme or catalyst for some reactions, but pretty rare for RNA (common for DNA tho)

Steps of Receptor-Mediated Endocytosis

a subtype of endocytosis that is very selective on what can come into the cell process begins in the ECF 1) ligand binds to membrane receptor 2) receptor-ligand migrates to cathrin-coated pit 3) endocytosis occurs (substance enters cell) 4) vesicle loses clathrin coat (coats go into pit) 5) receptors and ligands separate (endosome) 6) ligands go to lysosomes or Golgi for processing 7) transport vesicle with receptors moves to the cell membrane 8) transport vesicles and cell membrane fuse (membrane recycling) 9) exocytosis (substance exits cell) ends back in the ECF

Carrier Proteins

a subtype of membrane transporters that bind to its substrate on one side of the plasma membrane and transport it through the other side, without ever forming a connection between the ICF and ECF compartments they will never form an open channel between the two sides of the membrane they are only open to one side of the membrane at a time they are needed to move charged, polar, or large molecules across the channel since they cannot fit on their own they have specific binding sites for their substrates that they transport....these include large molecules that cannot fit through channels (ex: glucose, amino acids, peptides, ammonia) used in FACILITATED DIFFUSION

Channel Proteins

a subtype of membrane transporters that is a fluid/ water-filled tunnel-like passageway that directly links the ECF and ICF compartments substances can move through channels based on their concentration and/ or electrochemical gradient USED ONLY FOR IONS AND WATER when the channels are open, this is an example of passive/ facilitated diffusion they create a water-filled pore

Codons (+ their role in TRANSLATION)

a triplet of RNA bases that codes for a specific amino acid to make a protein little individual step-by-step instructions to code a three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal the basic unit of the genetic code IN TRANSLATION: codons have a base sequence that is complementary to their original DNA triplet of nucleotides each codon identifies a specific amino acid to add to the growing polypeptide AUG is the "start codon" UAA, UAG, and UGA are the "stop codons"

Steps of Phagocytosis

a type of endocytosis that is used by some immune cells like macrophages, neutrophils, and eosinophils 1) the phagocytic white blood cell encounters a bacterium that binds to the cell membrane 2) the phagocyte uses its cytoskeleton to push its cell membrane around the bacterium, creating a large vesicle (phagosome) 3) the phagosome containing the bacterium separates from the cell membrane and moves into the cytoplasm 4) the phagosome fuses with lysosomes containing digestive enzymes 5) the bacterium is killed and digested within the vesicle

Facilitated Diffusion

a type of passive transport when molecules move through the plasma membrane via membrane transporters they move down their concentration gradient net transport stops when the concentrations are equal on both sides of he membrane substances (ions and polar molecules) cannot move freely through the cell membrane the membrane transporters can help move them in either direction in or out of the cell

Transcytosis

a type of vesicular transport where substances move into, across, and then out of a cell it is a combination of endocytosis and exocytosis STEPS: process starts in plasma (ECF) 1) the plasma proteins are concentrated in caveolae, then undergo endocytosis and form vesicles 2) vesicles cross the cell with help from the cytoskeleton 3) vesicle contents are released into interstitial fluid by exocytosis process ends in interstitial fluid (ECF)

Signal Pathways

activated proteins in the target cell trigger a response FEATURES THAT ALL SIGNAL PATHWAYS SHARE: the signal molecule is a ligand that binds to a protein receptor (ligand = 1st messenger bc it brings the information to the target cell) ligand-receptor binding activates the receptor the receptor in turn activates one or more intracellular signal molecules the last signal molecule in the pathway creates a response by modifying existing proteins or initiating the synthesis of new proteins

Second Messenger

acts as a signal molecule in the cytoplasm PROTEIN KINASE: one role of second messenger is to activate this enzyme, which transfer a phosphate group from one molecule to another ION CHANNELS: second messengers can also manipulate the function of these membrane-bounded proteins, which quickly changes the conductance of charger particles across the membrane 2nd messenger can also act on intracellular organelles, like the endoplasmic reticulum, to release Ca2+ (which is a powerful messenger) into the cytosol

Store and Secretion Pathways for Proteins

after modification in the rough ER, proteins travel to the Golgi complex for sorting and packaging they travel to their final destination in vesicles

Why is osmotic equilibrium always maintained?

because water can move freely across membranes, soln concentrations are in a state of equilibrium

Autocrine vs. Paracrine Signals

both are local cell-to-cell chemical signals AUTOCRINE: (auto = self) signals that act on the same cell that secreted them PARACRINE: (para = beside) signals that are secreted by one cell and then diffuse to adjacent cells (that is in the immediate vicinity of the cell that secreted them)

How is membrane transport classified by? Which require ATP, which require other thing for transport, or both?

by the energy requirements (either ATP, or concentration gradients, electrochemical gradient, or osmosis) by physical pathways (through the membrane layer, through a membrane protein, or in a vesicle) ATP REQUIRED: active transport Vesicular Transport: exocytosis, endocytosis, phagocytosis Protein Mediated: direct/ primary active transport and indirect/ secondary active transport CONCENTRATION GRADIENT REQUIRED: passive transport Protein Mediated: facilitated diffusion Simple Diffusion ELECTROCHEMICAL GRADIENT REQUIRED: passive transport Protein Mediated: ion channel OSMOSIS REQUIREMED: passive transport Protein Mediated: aquaporin channel REQUIRE BOTH ATP and CONCENTRATION GRADIENT: indirect/ secondary active transport

Carbon Placements on DNA molecule

carbons are numbered in a clockwise fashion 1' C always has the nucleotide base attached to it 2' C has the hydroxyl group (-OH) attached 3' C either has one of the other hydroxyl groups attached, or another nucleotide 4' C has two other Cs attached 5' C always has a phosphate group attached to it

What kind of disequilibrium do the functional compartments of the body live in?

chemical and electrical disequilibrium molecules and ions are not at equal concentrations on either side of the membrane this disequilibrium is maintained at rest by MEMBRANE TRANSPORTERS for proper cell function

What allows separation of function?

compartmentation of different cellular processes in different parts of the cell The 10 Steps for Explaining How Protein Synthesis Demonstrates Subcellular Compartmentation: 1) mRNA is transcribed from genes in the DNA 2) mRNA leaves the nucleus and attaches to cytosolic ribosomes, initiating translation and protein synthesis 3) some proteins are released by free ribosomes into the cytosol or are targeted to specific organelles 4) ribosomes attached to the rough ER direct proteins destined for packaging into the lumen of the rough ER 5) proteins are modified as they pass through the lumen of the ER 6) transport vesicles move the proteins from the ER to the Golgi complex 7) Golgi cisternae migrate from the cis-face toward the cell membrane 8) some vesicles bud off the cisterna and move in a retrograde fashion 9) at the trans-face, some vesicles bud off to form lysosomes 10) other vesicles become secretory vesicles that release their contents outside the cell

Transducers

convert extracellular signals into intracellular messages, which then leads to a response

Contact-Dependent Signals (+ CAMs)

direct contact and local cell-to-cell communication they require interaction between membrane molecules on two cells cells can communicate via the surface molecules on one cell membrane binding to a membrane protein on another CELL-ADHESION MOLECULES (CAMs): an example of contact-dependent signals. surface molecules on one binds to the protein receptors on the other. they transfer signals in both directions, and both cells will change function in a specific way

What does ATP do for active transporting?

energy in the form of ATP is needed to "push" ions against their concentration gradient just like pushing water up-hill requires energy from a kind of pump the pump needed is carrier proteins

What happens during the life of a cell?

genes on DNA are used by cells to up-regulate the number of protein workers through the process of protein synthesis

What allows very fast long distance communication to occur?

having a narrow synaptic cleft and the length of axons example = spinal cord to and from arm or leg muscles

Membrane Ion Channel Questions

if a membrane channel were to open, Na+ ions would flow into the cell if a membrane channel were to open, K+ ions would flow out of the cell if a membrane channel were to open, Cl- ions would flow into the cell if a membrane channel were to open, Ca2+ ions would flow into the cell

What happens if the cell cycle is dysregulated?

it can lead to the formation of cancerous tumors

In transcription, the base sequence of the growing mRNA is dictated by what?

it is dictated by the base sequence in the DNA gene RNA Polymerase is programmed to transcribe DNA bases into RNA bases: A on DNA = U on mRNA T on DNA = A on mRNA C on DNA = G on mRNA G on DNA = C on mRNA

what is mRNA's role in TRANSLATION?

it is the substrate for translation

Factors affecting diffusion

lipid solubility molecular size concentration gradient membrane surface area composition of lipid bilayer diffusion of an uncharged solute across a membrane is proportional to the concentration gradient of the solute, the membrane surface are, and the membrane permeability to the solute

Introns

non-coding segments of an immature RNA molecule that are removed during alternative splicing, and stay in the nucleus. sequence of DNA that is not involved in coding for a protein. they are discarded and broken down after they are removed

What are the possible locations of receptors at target cells?

on the membrane inside the cytosol inside the nucleus (have slower responses related to gene activity)

How does DNA replication occur during S phase?

one DNA parent strand becomes two identical daughter strands replication occurs by unzipping and duplicating each DNA parent strand DNA HELICASES: enzymes that break hydrogen bonds between complementary bases to unzip the double helix DNA POLYMERASE: enzymes that insert and bind free nucleotides that match the DNA parent strands bases this enzyme can only read its DNA template in the 3' to 5' direction and synthesize a new strand in the 5' to 3' direction

Why is DNA replication "semi-conservative?"

one strand is from the original DNA (a template) and one strand is a new daughter strand, having one completed strand means that replication will be less prone to errors instead of fully synthesizing a new DNA copy

Histones

protein molecules that diffused DNA is tightly coiled and wrapped around chromatin

Frick's Law of Diffusion

rate of diffusion = (surface area x concentration gradient x membrane permeability) / (membrane thickness) membrane permeability = (lipid solubility) / (molecular size)

Cell Cycle/ Division

series of events that cells go through as they grow and divide the process by which DNA is replicated cells need to be able to copy and divide for growth and/or repair mostly all body cells need to have DNA present in them

Amplifier Enzyme (AE)

signal amplification begins when the first messenger ligand combines with a receptor an enzyme is then activated by the receptor-ligand complex that is embedded into the cell membrane, which produces the second messenger molecule one ligand is then amplified into many intracellular molecules

Why does each cell need to receive a complete copy of the genome?

so that they can maintain homeostasis GENOME = all 46 copies of chromosomes

Can ions move freely through the cell membrane?

some of them can water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ) electrical or chemical disequilibrium can be maintained, but... in most cases, cells and their membrane transporters must work (expend chemical energy in the form of ATP) to maintain unequal distribution of ions across membrane to function correctly IMPERMEABLE = if a membrane does not allow a substance to pass through it

Transcription

step 1 of gene expression this process occurs when the DNA base sequence is used to make a complementary piece of RNA RNA polymerase is an enzyme that reads and transcribes the specific gene and transcribe it into a copy of the gene called "pre-mRNA"

Interphase

step 1 of the cell cycle indefinite period/ Go phase when cells are not dividing MITOGENS: if a cell is wounded, this chemical signal indicates a need for the cell to be repaired....cell cycle then begins: has 3 sub-phases: G1 PHASE: indicates/ is still doing its normal cell function, cell growth, duplication of organelles, and protein synthesis (8+ hours) S PHASE: DNA is replicated and one copy of every chromosome is made. histones are synthesized and DNA is spread out as chromatin (6-8 hours) G2 Phase: proteins necessary for cell division are synthesized. more growth, and DNA begins to condense (2-5 hours)

mRNA Processing/ Editing/ Alternative Splicing

step 2 of gene expression may produce two proteins from one gene by ALTERNATIVE SPLICING the pre-mRNA that rolls off the DNA template is not the final version, these are the steps: 1) it starts as "pre-mRNA." 2) it is cut and spliced by snRNPs (groups of small nuclear ribonucleoproteins. then the parts that are kept are combined to form a complex called a SPLICEOSOME 3) introns are removed/ discarded by spliceosomes. 4) exons are kept and spliced/ joined (by sliceosomes) into one mature mRNA strand. 5) produces mRNA in its final form called "mature mRNA" 6) mature mRNA then leaves the nucleus and enters the cytoplasm

Mitosis

step 2 of the cell cycle nuclear division the division of somatic cells that results in two daughter cells that are identical to the parent cell 1-3 hours long has 4 steps: 1) PROPHASE: DNA finishes condensing into chromatids sister chromatids form and become microscopically visible as duplicate chromosomes nuclear envelope disappears spindle fibers extend from centrioles and bind to centromeres 2) METAPHASE: mitotic spindle fibers extend from the centrioles and attach to the centromere of each chromosome sister chromatids (chromosomes) line up single-file along equator of cell 3) ANAPHASE: spindle fibers pull the sister chromatids apart, which separates them then that identical copy of each chromosome moves towards each pole of the cell cytokinesis starts 4) TELOPHASE: chromatids arrive at opposite sides of cell new nuclear envelope forms DNA uncoils into chromatin chromosomes and chromatids are no longer visible the actual division of the parent cell into two daughter cells ends here cytokinesis stops

Cytokinesis

step 3 of cell cycle cytoplasm divides as an actin contractile protein ring tightens at the midline of the cell process by which two daughter cells pinch off, each with identical DNA, enter interphase begins during anaphase; completes by end of telophase

Translation

step 3 of gene expression the process that converts the mRNA "language" into amino acid "language" the process where RNA directs the assembly of amino acids into a protein chain after the ribosome is in contact/ binds with the first mature mRNA it saw, the ribosome reads the mRNA in 3 nucleotide segments (ex: AUG) called CODONS

Post-Translational Modification of Proteins

step 4 of gene expression since proteins are not usually in their final/ mature form when they are first produced, some need to undergo this step where they fold into complex shapes, may be split by enzymes into smaller peptide, or have various chemical groups added to them occurs in the lumen of the rough endoplasmic reticulum THE DIFFERENT WAYS A PROTEIN CAN BE MODIFIED IN THIS STEP: 1) protein folding creates tertiary structure via the help of CHAPERONE PROTEINS 2) cross-linkage creates strong covalent bonds (ex: disulfide bonds) that give give a protein its final structure 3) cleavage of protein fragments (ex: proteolytic activation) 4) addition of other molecules or groups called "conjugation" (ex: protein + carbohydrate = glycoprotein) 5) assembly into quaternary level of protein structure

Target Cells

the cells that receive or respond to chemical signals they have a specialized receptor for the signals

What determines the type and location for receptors?

the chemical characteristics of the signal molecule determine the type and location they can either be polar or non-polar: POLAR SIGNAL LIPOPHOBIC MOLECULES: can't pass through the membrane so they must bind to receptors embedded in the plasma membrane examples = peptide or amine hormones, neurotransmitters, neurohormones NON-POLAR LIPOPHILIC SIGNAL MOLECULES: can pass through (diffuse) the plasma membrane, so they can interact (bind) with cytosolic or nuclear receptors in multiple locations examples = steroid hormones, eicosanoids, gas signal molecules lipophilic and lipophobic signal molecules bind to receptors on the surface of the cell membrane

Exons

the coding segments of an mRNA molecule that actually code for the protein are are kept on the unprocessed mRNA strand for coding two exons join together and form a strand of mature mRNA, then exit the nucleus and move onto the next step of gene expression

What drives facilitated diffusion?

the concentration gradient drives facilitated diffusion through carrier proteins from a place of high to low concentrations

Resting Membrane Potential

the electrochemical gradient (difference) between the ECF and ICF -70 mV ion pumps work to main this resting potential for nerve and muscle cells, the inside of the cell is negatively-charged relative to the outside of the cell the charges are polarized (+ and - regions) between the inside and the outside of the cell

Ribonuclease

the enzyme that breaks down mRNA when it is no longer needed mRNA does not last forever because cells would like to have control over protein synthesis

RNA Polymerase

the enzyme that creates pre-RNA from the DNA template it unzips DNA to expose the correct gene it catalyzes the reaction that builds a complementary mRNA strand from the free ribonucleotides act as specifically programmed machines

What does CODON and ANTICODON matching ensure in the translation process?

the matching ensures that the correct amino acid is delivered at the correct spot in the growing peptide chain Anticodon on tRNA Codon on mRNA

Diacylglycerol

the other second messenger in the phospholipase C pathway that triggers protein kinase C (PKC) to phosphorylate proteins (effectively turning them on and off)

Signal Amplification

the process in cells that turns one signal molecule into multiple second messenger molecules it is an increase in intracellular chemical signals that then trigger target proteins to do their jobs this allows a small amount of signal to have a large effect AMPLIFICATION = the process of taking a small signal and making it big (turning up the "volume)

Gap Junctions (+ connexins)

the simplest method of local cell-to-cell signaling where the direct contact/ transfer of chemical or electrical signals happen through they are protein channels that form cytoplasmic bridges/ connections between adjacent cells they transfer both chemical and electrical signals between connected cells CONNEXINS: complexes of membrane-spanning proteins that are the physical connection

Active vs. Passive Transport

the two main types of membrane transporters, which are based on energy requirements, are: PASSIVE TRANSPORT: aka diffusion does not require energy from ATP substances move down concentration gradients (or electrochemical gradients for ions) the movement of molecules from high to low concentrations ACTIVE TRANSPORT: requires energy from ATP moves substances against a concentration gradient or moves substances in-bulk (vesicles)

Anti-Parallel DNA Strands

the two strands of DNA run anti-parallel one strand is upside down in comparison to the other strand the nucleotides in one strand are oriented with their 3' carbon facing up and their 5' carbon facing down the other strand has the opposite construction 3' end has a free hydroxyl group 5' end has a free phosphate group LEADING STRAND: can be synthesized continuously by DNA polymerase in the 5' to 3' LAGGING STRAND: can only be synthesized in small fragments this means that the two DNA parent strands need to be replicated in slightly different ways DNA Polymerase can only read its DNA template in the 3' to 5' direction and synthesize a new strand in the 5' to 3' direction one strand is synthesized continuously, and the other in synthesized in OKAZAKI FRAGMENTS

Antagonistic vs Tonic Control

there are several different ways to control signal transduction in an organ system through membrane-bound receptors and intracellular cascades ANTAGONISTIC CONTROL: (most common) this type uses the level of two different signals to push/ send a parameter (organ) in opposite directions example = parasympathetic and sympathetic innervations of the heart, their relative differences in signaling causes an increase or decrease contraction rate TONIC CONTROL: where activity in target cells is up-regulated and down-regulated by the intensity of one signal high levels have one effect on the target cells, whereas low levels have a different effect, but some level of the signal is always present (but can changes intensity) example = changes signal rates in blood vessel constriction

Primary (direct) vs. Secondary (indirect) Active Transport

these are both types of protein-mediated transport PRIMARY/ DIRECT ACTIVE TRANSPORT: specialized carrier proteins that use energy from ATP to move one or more solutes against their concentration gradient they use pumps or ATPases to do so called primary because ATP is used at the site of the transport or exchange example = Na+/K+ -ATPase uses the energy from inorganic phosphate (Pi) to move ions across a membrane. phosphorylation and dephosphorylation of the ATPase changes its conformation and the binding sites' affinity for ions SECONDARY/ INDIRECT ACTIVE TRANSPORT: uses carrier proteins to transport across membrane, but it does not sure energy from ATP directly (uses the energy from primary transport) these are always some form of cotransporters, never uniports 1st substance moves down its gradient (the power source by which a...) 2nd substance moves against its gradient the concentration of the 1st substance must be maintained for transport to continue the maintenance of the gradient requires primary active transport somewhere else in the cell's membrane it is called secondary active transport bc: movement of one substance is against its concentration or electrochemical gradient. it depends on energy from primary active transport. it does not use ATP at the site of transport example = sodium-glucose transporter (SGLT) this occurs in the lumen of the intestine or the kidney to start.... high [Na+], low [glucose] 1. Na+ binds to carrier protein outside of the cell and moves down the concentration gradient from a higher to lower concentration 2. Na+ binding creates a high-affinity site for glucose 3. glucose binding changes the carrier proteins confirmation so that binding sites now face the ICF 4. the carrier protein opens to the other side 4. Na+ is released into the cytosol, where [Na+] is low, this release changes the glucose-binding site to a low affinity 5. glucose is then released into the cytosol (glucose got a free ride because of Na+) glucose only got across because the Na+ gradient was maintained now [Na+] low and [glucose] high sodium moved against its gradient, and glucose moved down its gradient

Steps of an intracellular signal transduction pathway

these pathways form a cascade bc one chemical causes a change in the next, which then changes the next, until the final change in the cell's function is achieved Signal > inactive A > active A > inactive B > active B > inactive C > active C > Substrate > Product (conversion of substrate to product is the final step of the cascade)

What are the 3 types of carrier proteins?

these terms describe carrier proteins by the number and direction of substances moving through them 1) UNIPORT CARRIER PROTEINS: can only transport one kind of substrate across the membrane THESE BELOW ARE CLASSIFIED AS COTRANSPORTERS (move one or more kind of molecule across the plasma membrane at a time) 2) SYMPORT CARRIER PROTEINS: can move two or more types of substrates in the same direction across the membrane 3) ANTIPORT CARRIER PROTEINS: can move two or more types of substrates in opposite directions across the membrane

What are the multiple meanings for a "receptor?"

they can be cell membrane or intracellular receptor protein molecules on membranes or inside cells they can also be "sensors" that are clusters of specialized cells or structures that convert various stimuli into electrical signals TWO BRANCHES OF "SENSORS": 1) Central Receptors: in or close to the brain eyes, ear, nose, tongue, central chemoreceptors, central osmoreceptors, and central thermoreceptors 2) Peripheral Receptors: lie outside the brain chemoreceptors, osmoreceptors, thermoreceptors, baroreceptors, propioreceptors, and other mechanoreceptors

Vesicular Transport

transport of large particles and macromolecules across plasma membranes (require ATP) aka "bulk transport" 3 types: EXOCYTOSIS: exo = exit (the cell) secretory vesicles fuse with membrane and release its substance (ex: signal molecules or metabolic wastes) outside the cell. the opposite of endocytosis ENDOCYTOSIS: endo = enter (the cell) active process (requires ATP) where the membrane surface indents and forms a vesicle inside the cell receptor-mediated endocytosis: uses "clathrin-coated" pits to be very selective about what is brought into the cell other, less-selective versions of endocytosis, use "caveolae" to collect materials PHAGOCYTOSIS: phag = eat up or remove a type of endocytosis that is used by some immune cells like macrophages, neutrophils, and eosinophils STEPS: 1) cell engulfs bacterium or other particles into phagosome 2) sections of membrane stretch out, forming a pseudopods that encircle particle 3) particle may be transported to where it is needed 4) if a microbe is engulfed, phagosome will merge with a lysosome to destroy it

Homeostasis and the fluid compartment

under normal conditions, some conditions in the body are kept in equilibrium but may substances are not kept in equilibrium the concentration inside the cell (ions) does not match the concentration outside the cell unequal distribution in intracellular and extracellular environments must be maintained or restored quickly

How do substances that cannot move freely through the phospholipid bilayer enter or exit?

via membrane transporters facilitated diffusion

Sister Chromatids

when a particular chromosome is duplicated, the two duplicates form into sister chromatids and are joined at a central structure celled a centromere Identical copies of a chromosome held together at a protein tether (centromere) full sets of these are created during the S subphase of interphase.

Equilibrium Potential

when the membrane potential that exactly opposes the concentration of an ion gradient the membrane potential at which chemical and electrical forces are balanced for a single ion