MCAT Unit Two - Bio/Biochem

what are the two check points in the cell cycle? what occurs at each checkpoint? what molecules are responsible for the cell cycle check points?

G1/S checkpoint - is DNA good for synthesis? if damaged, cell is arrested until DNA is repaired G2/M checkpoint - has the cell achieved adequate size? - have organelles replicated? major players are p53, cyclins and cyclin dependent kinases (CDK) and transcription factors.

which GLUT transporter is found in liver and pancreatic β-cells?

GLUT 2

Which GLUT transporter is insulin dependent?

GLUT 4

What is the pentose phosphate pathway?

Generation of ribose-5-phosphate for nucleotide synthesis and NADPH for reducing power in anabolic pathways such as fatty acid synthesis. biochem 334

What are transposons?

Genetic elements in the genome that are mobile

What are microtubules? what are they made of? what processes do they participate in? what are centrioles? centrosomes?

Microtubules are hollow polymers of tubulin proteins. Microtubules radiate throughout the cell, providing the primary pathways along which motor proteins like kinesin and dynein carry vesicles. Cilia and flagella are motile structures composed of microtubules. CIlia are projections from a cell that are primarily involved in the movement of material along the surface of the cell; for ex cilia line the respiratory tract and are involved int eh movement of mucus. Flagella are involved in the movement of the cell itself, such as the movement of sperm cells through the reproductive tract.

What occurs in the M phase?

Mitosis Consist of four phases: prophase, metaphase, anaphase, and telophase ends with cytokinesis KEY CONCEPT: in autosomal cells, division results in two genetically identical daughter cells. In germ cells, the daughter cells are not equivalent.

what is the end result of mitosis? what cells does mitosis occur in?

Mitosis is the process by which two identical daughter cells are created from a single cell. Mitosis consists of four distinct phases - prophase, metaphase, anaphase, and telophase - and occurs in somatic cells, or cells that are not involved in sexual reproduction.

What is genetic recombination? what are virulence factors? episomes? what are the three types of genetic recombination?

Since bacteria usually reproduce using binary fission, they need a way to produce genetic diversity which is done through genetic recombination. Bacterial genetic recombination helps increase bacterial diversity and thus permits evolution of a bacterial species over time. these recombination processes include transformation, conjugation, and transduction

As we have seen prokaryotic cells differ from eukaryotic cells both structurally and biochemically. Prokaryotic cells reproduce via _______

asexual reproduction in the form of binary fission. In addition, prokaryotes are capable of acquiring and using genetic material from outside the cell through process of conjugation, transformation, and transduction

how is the cell wall organized in prokaryotes? what is it made up off? what are the two different types of cell walls found in bacteria?

there are two types of cell walls: gram positive and gram negative

What are steroid hormones? can they travel freely in the blood stream? are their effects short or long lived? can they pass through the plasma membrane freely?

Derivative of Cholesterol 1. Cortisol 2. Aldosterone 3. Testosterone 4. Estradiol 5. Cholesterol are all very hydrophobic (not water soluble), so they CANNOT travel freely in the blood. They need the help of binding proteins. BUT they can travel through the plasma membrane easily considering they are nonpolar molecules. Hense there receptors are usually located in the intracellular (in the cytosol) or intranuclear (in the nucleus) - note that hormones are generally inactive while attached to a carrier protein and must dissociate fro the carrier to function. Therefore, levels of carrier proteins can change the levels of active hormones. Generally lead to slow acting, longer lasting effects. KEY CONCEPT: peptide hormones have surface receptors and act via second messenger systems. Steroid hormones bind to intracellular receptors and function by binding to DNA to alter gene expression. Mnemonic: Insulin is a peptide hormone, and it has to be released at every meal in order to be active. Thus, it has a fast onset but it short lived (like most peptide hormones). Estrogen and testosterone are steroid hormones that promote sexual maturation. This is a slower, but longer lasting change (as is true for most steroid hormones)

What occurs in metaphase?

- centriole pairs at opposite ends - kinetochores interact with spindle fibers to align the chromosomes at the metaphase plate - chromosomes are equidistant between the two poles

What occurs in anaphase?

- centromeres split so that each chromatid has its own centromere - sister chromatids separate - kinetochore fibers shorten to pull towards opposite poles

what occurs in prophase?

- chromatin condenses into chromosomes - centriole pairs separate and move toward opposite poles - centrioles begin to form spindle fibers - nuclear membrane dissolves - spindle fibers contact the chromosome - kinetochores appear at the centromere as attachment points

What is the resting membrane potential?

-70mV and the voltage difference between the inside and outside of a nerve cell it is the electrical potential difference between the inside of the neuron and the extracellular space created by the Na+/K+ ATPase with the neuron being relatively negative relative to the outside. - the ATPase pumps 2K+ ions into the cell and 3Na+ ions out of the cell. This gives a positive net charge outside the cell, and a negative net charge inside cell. The equilibrium potential of potassium is around -90mV while the equilibrium potential of sodium is around 60 mV. The resting potential is closer to potassiums equilibrium potential because the cel lis slightly ore permeable to potassium. Either ions is never able to establish its own equilibrium, so both ions continue leaking across the cell membrane. MNEMONIC: to remember the direction of ion movement by Na/K ATPase; think pumpKin.

What is the role of flagella? what is chemotaxis? what are the three parts of the flagella?

-Primarily used to enable cell motility -In some cells they are used as a sensory organelle to detect chemical changes in the cell's environment The flagelle is composed of three parts: 1. Filament 2. basal body 3. book

what occurs during the infection phase of the viral life cycle?

-Virus must bind to specific receptors on cell wall, without which cell is immune -Enveloped viruses fuse with plasma membrane, allowing virion into host cell -Host cells will sometimes misinterpret virus binding and bring virus into cytoplasm via exocytosis -Bacteriophages use tail fibers to anchor themselves and inject genome using tail sheath -Enveloped viruses enter cytoplasm intact; bacteriophages only insert genetic material

glycolysis in erythrocytes

-red blood cells have biphosphoglycerate mutase, which produces 2,3-biphosphoglycerate (2,3-BPG) from 1,3-BPG in glycolysis -2,3-BPG binds allosterically to the β-chains of hemoglobin A (HbA) and decreases its affinity for oxygen -2,3-BPG does not bind well to fetal hemoglobin (HbF), thus HbF has a higher affinity for oxygen than maternal HbA, allowing transplacental passage of oxygen from mother to fetus

What are the four fundamental tenets of the cell theory?

1. All living things are made of cells 2. The cell is the basic functional unit of life 3. All cells arise from other preexisting cells 4. Genetic information is carried in the form of deoxyribonucleic acid (DNA) and is passed from parent to daughter cell

As we have mentioned, viruses must infect a host cell and use the host cell machinery in order to reproduce. What are the steps of the viral life cycle?

1. Infection 2. translation and progeny assembly 3. progeny release

One of the unique characteristics of eukaryotic cells is the formation of tissues with division of labor, as different cells in a tissue may carry out different functions - what are the four types of tissues?

1. epithelial tissue 2. connective tissue 3. muscle 4. nervous

While glycolysis contains many different steps, the MCAT predominantly test on the enzymes that are highly regulated or that serve an important energetic function. Therefore, we'll focus our attention on 5 of these enzymes - what are they?

1. hexokinase and glycokinase 2. phosphofuctokinase (PFK 1 and PFK 2) 3. glyceraldehyde-3-phosphate dehydrogenase 4. 3-phospoglycerate kinase 5. pyruvate kinase controlled enzymes catalyzing irreversible steps

Neurotransmission must be regulated - there are almost no circumstances under which constant signaling to the postsynaptic cell would be desirable. Therefore, the neurotransmitter must be removed from the synaptic cleft. There are three main mechanisms to accomplish this goal - what are they?

1. neurotransmitter can be broken down by enzymatic reactions. - the breakdown of acetylcholine (ACh) by AChE is a classic example. 2. Neurotransmitters can be brought back into the presynaptic neuron using reuptake carriers. - the reuptake of serotonin (5-HT) is a classic example. Dopamine (DA) and norepinephrine (NE) also use reuptake carriers. 3. neurotransmitters may simply diffuse out of the synaptic cleft. Nitric oxide (NO) a gaseous signaling molecule, fits this category

The endocrine system consists of organs, known as glands, that secrete hormones. Hormones are signaling molecules that are secreted directly into the bloodstream to distant target tissues. At target tissues, hormones bind to receptors, inducing a change in gene expression or cellular functioning. Not all hormones share the same structure and function. In order to understand how each hormone functions, it is first important to understand basic hormone structure. Hormones can be subdivided into three categories based on different criteria. What are the three different hormone categories based on their chemical identities?

1. peptide hormones. 2. steroid hormons 3. amino acid derivatives (also known as amine hormones)

what are the four important enzymes involved in gluconeogenesis?

1. pyruvate carboxylase 2. phosphoenolpyruvate carboxykinase (PEPCK) 3. fructose-1,6-bisphosphatase 4. glucose-6-phosphatase KEY CONCEPT: because glycolysis contains 3 irreversible steps (those catalyzed by hexokinase, phospofuctokinase-1, and pyruvate kinase) different enzymes must exist in gluconeogenesis to allow the body to revert pyruvate to glucose

The testes have two functional components - what are they? what occurs in each region?

1. seminiferous tubules 2. interstitial cells of Leydig sperm are produced in the highly coiled seminiferous tubules, where they are nourished by Sertoli cells. The cells of Leydig secrete testosterone and other male sex hormones (androgens). The testes are located in the scrotum, an external pouch that hangs below the penis, a position that allows it to maintain a temp of 2 to 4 C lower than the body. In fact, there is a layer of muscle around the vas deferens (ductus deferens) that can rise and lower the testis to maintain the proper temp for sperm development

what are the three bacterial shape classifications?

1. spherical bacteria - cocci 2. rod shaped bacteria - bacilli 3. spiral shaped bacteria - spirilli

fermentation

A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.

What is binary fission?

A form of asexual reproduction in which the parent divides into two approximately equal parts it is the simplest form of asexual reproduction seen in prokaryotes. the circular chromosome attaches to the cell wall and replicated which the cell continues to grow in size. Eventually, the plasma membrane and cell wall begins to grow inward along the midline of the cell to product two identical daughter cells. Because binary fission requires fewer events than mitosis, it can proceed more rapidly.

what are the three main methods by which a neurotransmitter's action can be stopped?

A neurotransmitter's action can be stopped by enzymatic degradation, reuptake, or diffusion.

what inhibits the pyruvate dehydrogenase complex?

ATP, acetyl-CoA, NADH, fatty acids

what occurs during the translation and progeny assembly phase of the viral life cycle?

After infection, translation of the viral genetic material must occur in order for the virus to reproduce. This requires translocation of the genetic material to the correct locations of the cell. - DNA viruses must enter the nucleus to be transcribed into mRNA. The mRNA then goes to the cytoplasm where it is translated into proteins - genetic material from + sense RNA viruses stays in the cytoplasm where is it translated into proteins by the host ribosomes.

what are some characteristics of prokaryotes? where is their DNA found?

Both bacteria and archaea are considered prokaryotes as they both lack membrane bound organelles

what is glycolysis? where does it occur? can all cels carry out glycolysis?

All cells can carry out glycolysis. In a few tissues, most importantly RBCs, glycolysis represents the only energy yielding pathway available because RBCs lack mitochondria, which is required for the citric acid cycle, electron transport chain, oxidative phosphorylation, and fatty acid metabolism (β oxidation). Glucose is a major monosaccharide that enters the pathway, but others such as galactose and fructose can also feed into it. Glycolysis is a cytoplasmic pathway that converts glucose into two pyruvate molecules, releasing a modest amount of energy captured in two substrate level phosphorylations and one oxidation reaction. If a cell has a mitochondria and oxygen, the energy carriers produced in glycolysis (NADH) can deed into the aerobic respiration pathway to generate energy for the cell. If either mitochondria or oxygen is lacking (such as in erythrocytes or exercising skeletal muscle, respectively), glycolysis may occur anaerobically, although some of the available energy is lost. Glycolysis also provides intermediates for other pathways. In the liver, glycolysis is part of the process by which excess glucose is converted to fatty acids for storage.

What are bacteria? what do they contain? how can they be classified?

All unicellular prokaryotic (no nucleus) organisms with peptidoglycan in their cell walls Bacteria can be classified in a number of different ways: 1. via their relationship with the human body and other organisms i.e. mutualistic symbiotes, pathogens, etc. 2. via shape i.e. cocci, bacilli, or spirlli 3. aerobes vs. anaerobes 4. gram + vs. gram -

what is glycogen?

Glycogen is a branched polymer of glucose, and it represents a storage form of glucose. Glycogen synthesis and degradation occurs primarily in the liver and skeletal muscle, although other tissues story smaller quantities. Glycogen is stored in the cytoplasm as granules. Each granule has a central protein core with polyglucose chains radiating outward to form a sphere, as shown in the pic. Glycogen granules composed entirely of linear chains have the highest density of glycose near the core. if the chains are branched, the glucose density is highest at the periphery of the granule, allowing more rapid release of glucose on demand. KEY CONCEPT: The glycogen in the liver and in skeletal muscle serve two quite different roles. Liver glycogen is broken down to maintain a constant level of glucose in the blood; muscle glycogen is broken down to provide glucose to the muscle during vigorous exercise.

What occurs during an action potential? what are the steps? what are the three states that a sodium channel? What are the two types of refractory periods?

If a cell is brought to threshold, voltage gated sodium channels open in the membrane. As the mane implies, these ion channels open in response to the change in potential of the membrane (depolarization) and permit the passage of Na ions. There is a strong electrochemical gradient that promotes the migration of Na into the cell. - from an electrical standpoint, the interior of the cell is more negative than the exterior of the cell, which favors the movement of positively charged Na+ cations into the cell - from a chemical standpoint, there is a higher concentration of Na outside the cell than inside, which also favors the movement of Na into the cell. As Na passes through these ion channels, the membrane potential becomes more positive; that is, the cell rapidly depolarizes. Na channels not only open in response to change in membrane potential, but are also inactivated by them. - When Vm approaches +35 mV, the Na channels are inactivated and will have to be brought back near the resting potential to be deinactivated. Thus, these Na channels can exist in 3 states; closed (before the cell reaches threshold, and after inactivation has been reveres) open (from threshold to approximately +35 mV) and inactivated (from approximately +35 mV to the resting potential) The positive potential inside the cell not only triggers the voltage gated Na channels to inactive, but also triggers the voltage gated K channels to open. Once Na has depolarizarzed the cell, there is an electrochemical gradient that favors the efflux of K from the neuron. As positively charged K cations are driven out of the cell, there will be a restoration of the negative membrane potential called repolarization. The efflux of K cause an overshoot of the resting membrane potential, hyperpolarizing the neuron. This hyperpolarization serves an important function: it makes the neuron refractory to further action potentials. There are two types of refractory periods. - During the absolute refractory period, no amount of stimulation can cause another action potential to occur. - During the relative refractory period, there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than its resting value. The Na/K ATPase acts to restore not only the resting potential but also the Na and K gradients that have been partially dissipated by the action potential. KEY CONCEPT: - Na+ wants to go into the cell because the cells is more negative inside (electrical gradient) and has a lower concentration of Na+ inside (chemical gradient) - Action potentials rely on both electrical and chemical gradients. The neuron starts at the resting potential, around -70 mV. At the resting potential, K is high inside the cell and low outside the cell, while Na is high outside the cell and low inside the cell. Once the cell reaches threshold, Na channels open and Na floods into the cell, making it more positive inside (depolarization). Then, Na channels are inactivated and the K channels open. This allows K to flow out of the cell, bringing the potential into the negative range (repolarization) and actually overshooting the resting potential (hyperpolarization). Na+/K+ ATPase then works to restore the resting potential.

So far, we have discussed the movement of ions at one small segment of the axon. For a signal to be conveyed to another neuron, the action potential must travel down the axon and initiate neurotransmitter release. This movement is called ______ ________.

Impulse propagation

What is fermentation and when does it occur?

It replenishes NAD+ so that glycolysis can continue when oxygen is not present

what is the role of glucose-6-phosphatase in gluconeogenesis?

KEY CONCEPT: Because gluconeogenesis requires acetyl-CoA to occur (to inhibit pyruvate dehydrogenase and stimulate pyruvate carboxylase), gluconeogenesis is inextricably linked to fatty acid oxidation. The source of acetyl-CoA cannot be glycolysis because this would just burn the glucose that is being generated in gluconeogenesis

what occurs during anaphase I of meiosis?

KEY CONCEPT: it is critical to understand how meiosis I is different from mitosis. The chromosome number is halved (reductional division) in meiosis I, and the daughter cells have haploid number of chromosomes (23 in humans). Meiosis II is similar to mitosis in that sister chromatids are separated from one another; therefore, no change in ploidy is observed.

What occurs in the G2 stage?

Known as the postsynthetic gap - check to ensure enough organelles and cytoplasm to divide into two daughter cells - check for errors in DNA replication

What occurs in the S stage?

Known as the synthesis stage - replicate genetic materials - each chromosome consist of two identical chromatids KEY CONCEPT: each chromatid is composed of a complete double stranded molecule of DNA. Sister chromatids are identical copies of each other. The term chromosome may be used to refer to either a single chromatid before S phase or the pair of chromatids attached at the centromere after S phase.

pathway of gluconeogenesis

Lactate is converted to pyruvate by lactate dehydrogenase. Alanine is converted to pyruvate by alanine aminotransferase. Glycerol 3-phosphate is converted to dihydroxyacetone phosphate (DHAP) by glycerol-3-phosphate dehydrogenase

In female sexual development - FSH stimulates what? what effect does this hormone have in the embryo? adults? LH stimulate the secretion of what?

MNEMONIC: Estrogen establishes and progesterone protects the endometrium

Are neurons physically connected to one another? if not how do they communicate with each other?

Neurons are not physically connected to one another. Between the neurons, there is a small space into with the terminal portion of the axon releases neurotransmitters, which bind to the dendrites of the adjacent neuron (the postsynaptic neuron). This space is known as the synaptic cleft; together, the nerve terminal, synaptic cleft, and postsynaptic membrane are known as the synapse. Neurotransmitters released from the axon terminal traverse the synaptic cleft and bind to receptors on the postsynaptic neuron.

What is an action potential?

Neurons use all-or-nothing messages called action potentials to replay electrical impulses down the axon to the synaptic bouton. As we will explore in the following section, action potentials ultimately cause the release of neurotransmitters into the synaptic cleft.

What are peptide hormones? what are the hormones that fall under the group peptide and protein hormones? can they travel freely in the blood?

Peptide hormones are made up of amino acids, ranging in size from quite small (such as ADH) to relatively large (such as insulin). made in a version called a pro-hormone first which gets packaged and cleaved to become an activated hormone in the golgi ex. Insulin, Glucagon, TRH, CRH, GHRH, GH, ACTH, Prolactin, FSH, LH, ADH, Oxytocin Do not usually need binding proteins to travel through the blood (hence you can say they are hydrophilic) BUT there are unable to cross the plasma membrane on their own considering they are charged molecules. Instead, they must act through a second messenger system - known as a signaling cascade where at each step there is a possible amplification. Some common second messengers are cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3), and calcium. The effects of peptide hormones are usually rapid but short-lived bc these hormones act through second messenger cascades, which are transient. It is quicker to turn them on or off compared with steroid hormones, but their effects do not last without relatively constant stimulation Bc peptide hormones are generally water-soluble, peptide hormones can travel freely in the bloodstream and usually do not require carriers. This is in stark contrast to steroid hormones, which are lipid-soluble.

What are the four phases of bacterial growth? what occurs in each phase?

Phases of bacterial growth 1. Lag phase: bacteria get used to environment; little growth 2. Exponential phase: bacteria use available resources to multiple at an exponential rate 3. Stationary phase: Bacterial multiplication slows as resources are used up 4. Death phase: bacteria die as resources become insufficient to support the colony

Prior to release, neurotransmitter molecules are stored in _______ _______ _____ in the nerve terminals. What occurs when the action potential reaches the nerve terminal?

Prior to the release, neurotransmitter molecules are stored in membrane-bound vesicles. When the action potential reaches the nerve terminal, voltage gated calcium channels open, allowing calcium to flow into the cell. This sudden increase in intracellular calcium triggers fusion of the membrane bound vesicles with the cell membrane at the synapse, causing exocytosis of the neurotransmitter. Once released into the synapse, the neurotransmitter molecules diffuse across the cleft and bind to receptors on the postsynaptic membrane. This allows the message to be passed from one neuron to the next. As we stated earlier, neurons may be either excitatory or inhibitory; this distinction truly coms at the level of the neurotransmitter receptors. If the receptor is a ligand-gated ion channel, the postsynaptic cell will either be depolarized or hyperpolarized. If it is a G protein coupled receptor, it will cause either changed in the levels of cyclic AMP (cAMP) or an influx of calcium.

What are archaea?

Prokaryotes characterized as extremophiles that share some bacterial and some eukaryotic traits.

The first major distinction we can make between living organisms is whether they are composed of prokaryotic or eukaryotic cells - what are the main differences between these cells?

Prokaryotes: - contain bacteria and archaea - single celled - do not contain a nucleus - lake membrane bound organelles Eukaryotes: - unicellular or multicellular - contain a true nucleus - contain numerous membrane bound organelles

what are positive sense viruses? negative sense viruses? Retroviruses?

Single-Stranded RNA viruses can be positive sense or negative sense viruses - positive-sense RNA virus genomes can be directly translated into proteins by host ribosomes; similar to mRNA - negative-sense RNA viruses act as a templet which must be used to create the complementary strand which can then be used for protein synthesis. These viruses must carry an RNA replicase in their viron to ensure the complementary strand is synthesized Retroviruses - single-stranded RNA viruses that contain an enzyme known as reverse transcriptase. this enzyme synthesizes DNA from RNA. The DNA is then integrated into the host genome where it is replicated and transcribed as if it were the host's own DNA. this allows the cell to be infected indefinitely so the only way to remove the infection is to kill the infected cells. This is the method of infection or HIV

What occurs in telophase and cytokinesis?

Telophase: - reverse of prophase - spindle apparatus disappears - nuclear membrane reforms - chromosomes uncoil Cytokinesis: - separation of cytoplasm forming two identical daughter cells

Each neuron has a shape that matches its function, as dictated by the other cells with which that neuron interacts. there are a variety of different types of neurons in the body, but they all share some specific features - what is/are the soma, dendrites, axon hillock, axon, myelin sheath, nodes of ranvier, and the nerve terminal?

The anatomy of a neuron is shown in the picture. Like all other cells (besides mature RBCs) neurons have nuclei. The nucleus is located in the cell body, also called the soma. - the soma is also the location of the endoplasmic reticulum and ribosomes. The cell has many appendages emanating directly from the soma called dendrites. dendrites received incoming messages from other cells. The information received from the dendrites is transmitted through the cell body before it reaches the axon hillock. - the axon hillock integrates incoming signals. The axon hillock plays an important role in action potentials, or the transmission of electrical impulses down the axon. - the signals arriving from the dendrites can either be excitatory or inhibitory; the axon hillock sums up these signals, and it the result is excitatory enough (reaching threshold) it will initiate an action potential. The axon is a long appendage that terminated in close proximity to a target structure (a muscle, gland, or another neuron). Most mammalian nerve fibers are insulated by myelin, a fatty membrane, to prevent signal loss or crossing of signals. - Just like insulation prevents wires next to each other from accidentally discharging each other, the myelin sheath maintains the electrical signals within one neuron. In addition, myelin increases the speed of conduction in the axon. Myelin is produced by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. At certain intervals along the axon, there are small breaks in the myelin sheath with exposed areas of axon membrane called nodes of Ranvier which are critical for rapid signal conduction. Finally, at the end of the axon is the nerve terminal or synaptic bouton (knob). This structure is enlarged and flattened to maximize transmission of the signal to the next neuron and ensure proper release of neurotransmitters, the chemicals that transmit information between neurons.

What is the cell cycle? what are its four parts? what states are apart of interphase? what occurs in interphase?

The cell cycle consists of four stages for actively dividing cells: G1, S, G2, and M. The first three G1, S, and G2 are collectively known as interphase. Interphase is the longest part of the cell cycle; even actively dividing cells spend about 90% of their time in interphase. Cells that do not divide (such as nerve and muscle cells) spend all of their time in an offshoot of G1 called Go. During the Go stage, the cell is simply living and carrying out its function without any preparation for division. During interphase, individual chromosome are not visible with light microscopy bc they are in a less condensed form known as chromatin. This is bc the DNA must be available to RNA polymerase so that genes can be transcribed. During mitosis, however, it is preferable to condense the DNA into tightly coiled chromosomes to avoid losing any genetic material during cell division.

how are amino acid derivative hormones synthesized?

are made by modifying amino acids, such as the addition of iodine to tyrosine (in thyroid hormone production)

What is the role of hexokinase and glycokinase in glycolysis? where are each of them found in the body and what inhibits them?

The first step in glucose metabolism in any cell is the transport of glucose across the membrane and then the phosphorylation by kinase enzymes inside the cell to prevent the glucose from leaving via the transporter. - remember that kinases attach a phosphate group from ATP to their substrates. Glucose enters the cell by facilitated diffusion or active transport; in either case, these kinases convert glucose to glucose-6-phosphate Because GLUT transporters are specific for glucose and not phosphorylated glucose, the glucose gets "trapped" inside the cell and cannot leak out. Hexokinase is widely distributed in tissues and is inhibited by its product, glucose-6-phospate Glucokinase is found only in liver cells and pancreatic β islet cells; in the liver, glucokinase is induced by insulin. The table in the picture identifies the differences between these enzymes. These coincide with the differences between the glucose transports in these tissues.

What is gluconeogenesis?

The formation of glucose by non-glucose precursors. Proteins and fats.

In females, the gonads are the _____, which secrete _____.

The gonads, known as ovaries, produce estrogen and progesterone. the ovaries are located in the pelvic cavity; each consists of thousands of follicles, which are multiplayer sacs that contain, nourish, and protect immature ova (eggs). Between puberty and menopause, one egg per month is ovulated into peritoneal sac, which lines the abdominal cavity.

What is the function of the mitochondria? What are the divisions of the mitochondria? what are cristae? In the electron transport chain - protons are pumped from ____ to _____ generating _____.

The mitochondria is the powerhouse of the cell, in reference to its important metabolic functions. The mitochondria consist of two layers: The outer and inner membranes. - the outer membrane serves as a barrier between the cytosol and the inner environment of the mitochondrion. - the inner membrane, which is arranged into numerous infoldings called cristae, contains the molecules and enzymes of the electron transport chain. The cristae are highly convoluted structures that increase the surface area available for electron transport chain enzymes. The space between the inner and outer membranes is called the intermembrane space; the space inside the inner membrane is called the mitochoniral matrix. The pumping of protons from the mitochondrial matrix to the intermembrane space establishes the proton -motive force; ultimately, these protons flow through ATP synthase to generate ATP during oxidative phosphorylation OVERALL the mitochondria is the powerhouse of the cell and site of aerobic respiration

What is the function of the nucleus? is it membrane-bound? if so what is the name of its membrane? what is found inside the nucleus?what are nuclear pores?

The nucleus is the control center of the cell and it contains all of the genetic material necessary for replication. The nucleus is membrane-bound as it is surrounded by the nuclear membrane or envelope, a double membrane that maintains the nuclear environment separate and distinct from the cytoplasm. Nuclear pores in the nuclear membrane allow selective two-way exchange of material between the cytoplasm and the nucleus. The genetic material (DNA) contains coding regions called genes. Linear DNA is wound around organizing proteins known as histones and is then further wound into linear strands called chromosomes. the location of DNA in the nucleus permits the compartmentalization of DNA transcription separate from RNA translation. Finally, there is a subsection of the nucleus known as the nucleolus, where the ribosomal RNA (rRNA) is synthesized.

lytic vs lysogenic cycle

The virus enters the cell and immediately breaks down the cell's DNA and takes over the machinery to replicate. In the Lysogenic Cycle, viruses stay dormant with their DNA attached to the host cell's, when the cell divides, the viral DNA is replicated with the host cell's and passed onto the daughter cells.

neurons are not the only cells in the nervous system. Neurons must be supported and myelinated by other cells. These cell are often called _______ cells or _______. What is the basic function of astrocytes, ependymal cells, microglia, and olidogendrocyes and schwann cells?

These cell are often called glial cells or neuroglia.

During the reproductive years (from menarche to menopause), estrogen and progesterone levels rise and fall in a cyclic pattern. In response, the endometrial lining will grow and be shed. This is known as _______ and can be divided into four events - what are they?

This is known as the menstrual cycle and the four events that occur are the follicular phase, ovulation, the luteal phase, and menstruation. The MCAT likes to test you ability to identify graphs of the blood concentrations of FSH, LH, estrogen, and progesterone throughout the menstrual cycle. Be sure to know when each peaks

what is the structure of a virus? how do they reproduce? wha are virons? bacteriophages?

Viruses Contain: 1. genetic material - can be circular or linear; single or double stranded; RNA or DNA 2. Protein coat known as the capsid 3. sometimes contain an envelope - made of phospholipids and is very sensitive to heat, detergents, and are thus easier to kill.

What is meiosis? what type of cells does this occur in? how does it differ from mitosis?

Whereas mitosis occurs in somatic tissue and results in two identical daughter cells; meiosis occurs in gametocytes (germ cells) and results in up to four nonidentical sex cells (gametes). Meiosis stares some similarities with mitosis. In both processes for instance, genetic material must be duplicated, chromatin is condensed to form chromsomes, and microtubules emanating from centrioles are involved in dividing genetic material. HOWEVER, the MCAT tends to ask about the differences between these two processes. In constrast, mitosis, which consists of one round each of replication and division, meiosis consists of one round of replication followed by two rounds of division, as shown in the pic. Meiosis I results in homologous chromosomes being separated generating haploid daughter cells; this is known as reductional division. Meiosis II is similar to mitosis, in that it results in the separation of sister chromatids without a change in ploidy, and is therefore known as equational division.

What is the function of the Endoplasmic Reticulum? What are its divisions and their functions?

a series of membranes continuous with the nuclear envelope. - two different regions 1. Rough ER - is studded with ribosomes (allows for protein translation) 2. Smooth ER - is used for lipid synthesis and detoxification

What is a neuron?

a specialized cell that is capable to transmitting electrical impulses and then translating those electrical impulses into chemical signals in this section we will consider the structure of the neuron as well as how neurons communicate with other parts of the nervous system

what occurs in prophase I of meiosis?

bc of crossing over, each daughter cell will have a unique pool of alleles (genes coding for alternative forms of a given trait) from a random mixture of maternal and paternal origin. In classical genetics, crossing over explains Mendel's second law (of independent assortment), which states that the inheritance of one allele has not effect on the likelihood of inheriting certain alleles for other genes.

What is the function of peroxisomes?

break down long chain fatty acids because they contain hydrogen peroxide. they are found in all eukaryotic cells considering they serve as an energy source of last resort

What is glycogenolysis? what is the rate limiting enzyme in this process?

breakdown of glycogen to glucose

what is the function of the lysosome? What occurs if the contents of the lysosome is released?

breaks down cellular waste and debris through the use of hydrolytic enzymes. It is membrane bound to prevent damage to the cell

how can cells with GLUT 4 transporters increase their intake of glucose?

by increasing the number of GLUT 4 transporters on their surface

What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?

calcium is responsible for fusion of neurotransmitter vesicles with the nerve terminal membrane

what occurs in the cell cycle is not controlled?

cancer can form

Glucose entry into most cells is driven by

concentration and is independent of sodium, unlike absorption from the digestive tract. Normal glucose concentration in peripheral blood is 4-6 mM. There are four glucose transporters, called GLUT 1 through GLUT 4. GLUT 2 and GLUT 4 are the most significant because they are located only in specific cells are are highly regulated

what is the role of the pyruvate dehydrogenase complex?

converts pyruvate into acetyl-CoA which can then enter the citric acid cycle if ATP is needed or for fatty acid synthesis if sufficient ATP is present

What are amine hormones (amino acid derivative hormones)? can they travel freely in the blood? where are their receptors located? what are some examples? are their effects short or long lived?

derivatives of tyrosine - Thyroid hormones need binding proteins to help them travel in the blood 1. Thyroxine (T4) 2. Triiodothyronine (T3) 3. Norepinephrine 4. Epinephrine 5. Dopamine thyroid hormones Catecholamine Biogenic Amines

In humans there are two types of cells - what are they?

diploid (2n) and haploid (n) In animals, autosomal cell said to be diploid (2n) which means that they contain two copies of each chromosome. Germ cells, on the other hand, are haploid (n) containing only one of each chromosome. In humans, we inherit 23 chromosomes from each parent. Eukaryotic cells replicate through the cell cycle, a specific series of phases during which a cell grows, synthesizes DNA, and divides. Derangement of the cell cycle can lead to unchecked cell division and may be responsible for the formation of cancer

We can also classify hormones by target tissue - what are direct hormones? tropic hormones?

direct hormones: are secreted into the blood stream and travel to a target tissue, where they have a direct effect tropic hormones: cause secretion of another hormone that then travels to the target tissue to cause an effect.

As sperm are formed, they are passed to the ____. what occurs here?

epididymis, where their flagella gain motility, and they are then stored until ejaculation.

What is glycogenesis?

formation of glycogen from glucose there are two important enzymes involved in this process: glycogen synthase and branching enzymes

what is the role of glycogen phosphorylase?

glycogen phosphorylase is used in glycogenolysis it breaks down a-1,4-glycosidic linkages stops near branch points

gram positive vs gram negative cell wall

gram + - thick peptidoglycan cell wall - plasma membrane - purple (retain the crystal violet dye) - the cell wall also contains lipoteichoic acid which upon exposure in the human body elicits an immune response gram - - thin peptidoglycan cell wall - plasma membrane - outer membrane - also have a lipopolysaccharide layer which can produce a large immune response - stains pink KEY CONCEPT: bacteria contain a cell wall, the composition of which is different in gram + and gram - bacteria. Specific components of the cell wall can trigger an inflammatory response

What is the role of the branching enzymes in glycogenesis?

hydrolyzes (breaks) an α-1,4 glycosidic link, forms an α-1,6 glycosidic link to create branch

what is the role of the debranching enzymes in glycogenolysis?

it is a two enzyme complex 1. glucosyntransferase breaks α-1,4 bond at branch points and forms new α-1,4 bond 2. gucosidease hydrolyzes α-1,6 bonds releasing free glucose

lytic and lysogenic cycle

main methods of reproduction of a bacteriophage 1. lytic cycle - there is little regard for the cell. The cell is filled with virons making the cell lyse open. The virions are then released into the environment where they can affect more cells. 2. Lysogenic cycle - the viral genome is integrated into the host genome creating a provirus or prophage. This initiates the lysogenic cycle which allows the cell to reproduce and live in harmony with the host cell. Certain factors such as radiation, light, or chemicals can cause the cells to revert back to the lytic cycle.

the mitochondria are different from other parts of the cell in that they are __________. How do they replicate? How can they cause destruction?

mitochondria are semiautonomous. They contain some of their own genes and replicate independently of the nucleus via binary fission. As such, they are paradigmatic examples of cytoplasmic or extranuclear inheritance - the transmission of genetic material independent of the nucleus. (mitochondrial DNA can also be inherited from the mother). mitochondria are thought to have originated when the engulfing of an aerobic prokaryote by an anaerobic prokaryote resulted in a symbiotic relationship. In addition to keeping the cell alive by providing energy, the mitochondria are also capable of killing the cell by the release of enzymes from the electron transport chain. this release kick starts the process known as apoptosis, or programmed cell death

What is depolarization? hyperpolarization? what is threshold and how is an action potential triggered?

neurons can receive both excretory and inhibitory input. Excitatory input causes depolarization (raising the membrane potential, Vm, from its resting potential) and thus make the neuron more likely to fire an action potential. Inhibitory input causes hyperpolarization (lowering the membrane potential from its resting potential) and thus makes the neuron less likely to fire an action potential. If the axon hillock receives enough excitatory input to be depolarized to the threshold value (usually in the range of -55 mV to -40 mV), an action potential will be triggered.

what does it mean if something is oxidized? reduced?

oxidation is the loss of electrons while reduction is the gain of electrons it might be easier to think of oxidation as increasing bonds to oxygen or other heteroatoms (atoms besides C and H) and reduction as increasing bonds to hydrogen. Thus, the conversion of NAD+ to NADH is a reduction reaction

The membranes of eukaryotic cells consist of what? what is the function of the cytosol? how do eukaryotic cells reproduce?

phospholipid bilayers - this membrane is unique in that its surfaces are hydrophilic, electrostatically interacting with the aqueous environment inside and outside of the cell, which its inner portion is hydrophobic, which helps to provide a highly selective barrier between the interior of the cell and the external environment The cytosol allows for the diffusion of molecules throughout the cell. Within the nucleus, genetic material is encoded in deoxyribonucleic acid (DNA), which is organized into chromosomes. Eukaryotic cells reproduce by mitosis, allowing for the formation of two identical daughter cells.

what occurs during the progeny release phase of the viral life cycle?

progeny release may occur in multiple different ways 1. viral invasion may initiate cell death, spilling the viral progeny out of the cell 2. lyses: the host cell may lyses as a result of being filled with extremely large numbers of virons. - this is a disadvantage to the virus bc it can no longer use the cell to carry out its life cycle 3. extrusion: virus leaves by fusing with the plasma membrane - this allow the host cell to stay alive and is an advantage to the virus bc it allows for continued use of the host cell by the virus. A virus in this state is said to be in a productive cycle.

what is the function of epithelia tissue? what are the different ways we can classify epithelia tissue?

protects us against pathogens

what is the function of the cytoskeleton? what are the three components for the cytoskeleton?

provides structure to the cell and maintains shape 1. microfilaments 2. microtubules 3. intermediate filaments

what is the role of glycogen synthase in glycogenesis?

rate limiting enzyme forms linear α-1,4 glycosidic links

What occurs in meiosis II?

sister chromatids separate Meiosis II is very similar to mitosis in that the sister chromatids - rather than homologues - are separated from each other

What occurs during ejaculation?

sperm travels through the vas deferens and enters the ejaculatory duct at the posterior edge of the prostate gland. the two ejaculatory ducts then fuse to form the urethra, which carries the sperm through the penis as they exit the body. In males, the reproductive and urinary system share a common pathway; this is not the case in females.

What is connective tissue? what are some examples of connective tissue?

supports body and provides framework

What is the difference between temporal and spatial summation?

temporal summation is the integration of multiple signals close to each other in time spatial summation is the integration of multiple signals close to each other in space

In males, the primitive gonads develop into the

testes

What neural structure initiates the action potential?

the action potential is initiated at the axon hillock

what occurs during anaphase II of meiosis?

the centromeres divide, separating the chromosomes into sister chromatids. These chromatids are pulled to opposite poles by spindle fibers

what occurs in metaphase II of meiosis?

the chromosomes line up on the metaphase plate

What occurs in prophase II of meiosis?

the nuclear envelope dissolves, nucleoli disappear, the centrioles migrate to opposite poles, and the spindle apparatus begins to form

What entity maintains the resting membrane potential? What is the approximate voltage of the resting membrane potential?

the resting membrane potential is maintained by the Na+/K+ ATPase at approximately -70 mV.

What is the function of the golgi apparatus? what occurs in the lumen? what about of the cis side? trans side?

this is the post office of the cell - materials from the ER are transfered to the golgi to be packaged and transported to other parts of the cell. - cellular products are modified in the golgi and repackaged - repackaged vesicles are transported to the correct cellular locations - the golgi has a couple structures to be aware off 1. cisternae: foldings that increase surface area 2. lumen: modification adding carbohydrates, phosphates, and sulfates 3. Cis side: side receiving incomes vesicles 4. Trans side: side releasing vesicles SO newly synthesized signaling proteins would travel from the RER to the CIS side of the golgi, be repackaged/modified, and then exit through the TRANS side of the golgi

What occurs in the GI phase of the cell cycle?

this stage is known as the presynthetic gap - create organelles for energy and protein production - increase in size - restriction point to pass into S stage

what is the role of the ATPase?

to maintain resting membrane potential. neither ion (K or Na) ever "wins" the tug of war. Instead a balance of these two effects is reached at around -70 mV for the average nerve cell. This balance, or the net effect of both Na and K equilibrium potentials, is the resting membrane potential. The resting potential is closer to Potassium's (K) equilibrium potential because the cell is slightly more permeable to potassium. Neither ion is ever able to establish its own equilibrium, so both ions continue leaking across the cell membrane. Given the continual ion leaking at the membrane, there must be a means of moving both Na and K ions back against their gradient if a resting potential is to be maintained. Na+/K+ ATPase continually pumps Na and K back to where they started; K into the cell and Na out of the cell, to maintain their respective gradients. In fact, in your body more ATP is spend by the Na/K ATPase to maintain these gradients than for any other single purpose.

What is conjugation?

transfer of DNA between bacteria using a pilus conjugation is the bacterial form of mating (sexual reproduction). It involves two cells forming a conjugation bridge between them that facilitates the transfer of genetic material. The transfer is unidirectional, from the donor male (+) to the recipient female (-). the bridge is made from appendages called sex pili that are found on the donor male. To form the pilus, bacteria must contain plasmids known as sex factors that contain the necessary genes. The best-studied sex factor is the F (fertility) factor in E. coli. Bacteria processing this plasmid are termed F+ cells; those without are called F- cells. During conjugation, the F+ cell replicated its F factor and donates the copy to the F- cell, converting it to an F+ cell. This enables the cell obtaining the new plasmid to then transfer copied to other cells. This method of genetic recombination allows for rapid acquisition of antibiotic resistance or virulence factors throughout a colony because other plasmids can also be passed through the conjugation bridge.

What is transformation?

uptake of DNA from environment

what triggers meiosis II in oogenesis?

when a sperm cell penetrates these layers with the help of acrosomal enzymes