MCAT Bio/Biochem Khan academy and UWorld

Aldosterone

"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure

What is the purpose of the 5' cap on mRNA?

-To protect from breakdown of exonucleases which breakdown foreign DNA. -To aid in ribosomal binding. -To aid in transport out of the nucleus.

Hardy Weignberg populations have three assumptions:

1) No selection 2) No mutation 3) Large population

1 FADH2 produces how many ATP?

2 ATP

1 NADH produces how many ATP?

3 ATP

A Bronsted-Lowry _______ tends to donate hydrogen ions, which have positive charges in solution.

A Bronsted-Lowry acid tends to donate hydrogen ions, which have positive charges in solution.

A Lewis _______ tends to accept electrons in solution, leaving the molecule with a net negative charge

A Lewis acid tends to accept electrons in solution, leaving the molecule with a net negative charge

Chemokines:

A chemical secreted by blood vessel endothelium and monocytes during an immune response to attract phagocytes (such as leukocytes) to an area.

myelin sheath

A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next. It essentially insulates the signal from dissipating or weakening.

A negative delta H describes what?

A release of energy when going from reactants to products. Delta H often describes the bond energy

Fatty acid oxidation and synthesis occur in which subcellular compartments, respectively? A.In the mitochondria and the cytosol B.In the nucleus and the mitochondria C.In the cytosol and the nucleus D.In the cytosol and the mitochondria

A. In the mitochondria and the cytosol Fatty acid oxidation is the catabolic breakdown of fatty acids to acetyl-CoA, whereas fatty acid synthesis is the anabolic production of fatty acids from acetyl-CoA units. These opposing pathways are regulated in part by compartmentalization. The enzymes required for fatty acid oxidation are found in the mitochondria, where newly generated acetyl-CoA molecules can enter the citric acid cycle and the electron transport chain to produce ATP. In contrast, the enzymes for fatty acid synthesis are in the cytosol, where excess acetyl-CoA is converted to malonyl-CoA and then linked to other acyl units to form fatty acids.

Which series depicts the order in which the precursors of steroid hormones are synthesized? A.Isoprene → monoterpene → squalene → cholesterol B.Cholesterol → isoprene → monoterpene → squalene C.Monoterpene → isoprene → squalene → cholesterol D.Isoprene → cholesterol → monoterpene → squalene

A. Isoprene → monoterpene → squalene → cholesterol Steroid hormones are involved in multiple critical signaling pathways in the body, including those related to physical development, reproduction, and stress. All steroid hormones are synthesized from cholesterol and share a common backbone structure consisting of four fused rings: 3 six-member rings and 1 five-member ring. The basic unit of cholesterol is a branched five-carbon molecule belonging to a class known as isoprenes. Isoprenes can combine with each other to form larger units known as terpenes. Terpenes consisting of two isoprene units are called monoterpenes, those consisting of two monoterpenes (or four isoprenes) are called diterpenes, and those consisting of three monoterpenes (six isoprenes) are called triterpenes. During cholesterol synthesis, a triterpene known as squalene forms. Squalene undergoes multiple steps, including demethylation, methyl rearrangements, and cyclization, to form cholesterol. The correct order of synthesis for the precursors of steroid hormones is isoprene → monoterpene → squalene → cholesterol.

In a neuron, mitochondrial biogenesis is believed to occur primarily in the cell body, but mitochondria are often positioned at the presynaptic terminal, a distal site with high metabolic demand. Given this information, which molecular mechanism is most likely responsible for mitochondrial transport from the cell body to the presynaptic terminal? A.Kinesin motors transport mitochondria along microtubules B.Kinesin motors transport mitochondria along microfilaments C.Dynein motors transport mitochondria along microfilaments D.Dynein motors transport mitochondria along microtubules

A. Kinesin motors transport mitochondria along microtubules A eukaryotic cell's cytoskeleton is an intracellular scaffolding (network) of fibers interspersed throughout the cytoplasm. The cytoskeleton is composed of three types of fibers: Microfilaments, intermediate filaments, and microtubules. Together, these fibers function to organize cellular components, support cellular motility (eg, cell movement, intracellular transport), and give the cell its shape. Microtubules are structural cytoplasmic filaments composed of tubulin subunits. These filaments have a number of critical functions, including serving as tracks for intracellular transport of organelles and vesicles. The movement of intracellular cargo along microtubules is mediated by two motor proteins: Kinesin: Moves intracellular cargo along microtubules in anterograde axonal transport (ie, away from the nucleus and toward distal sites). Dynein: Participates in retrograde axonal transport of intracellular cargo (ie, from distal sites toward the nucleus) (Choice D). According to the question, mitochondria are transported from the cell body toward the presynaptic terminal. Because mitochondria are being transferred from the nucleus and toward the synaptic terminal, this anterograde transport is most likely being performed by kinesin motors moving along the microtubules.

Which event could alter a protein's primary structure? A.Site-directed mutagenesis of the gene that encodes the protein B.A conformational change in the protein induced by ligand binding C.Protein denaturation by guanidinium chloride D.Reduction of disulfide bonds by β-mercaptoethanol

A. Site-directed mutagenesis of the gene that encodes the protein Because primary structure is the sequence of amino acids, it can only be disrupted by events that alter this sequence. These events include cleavage of peptide bonds by proteases and changes in the amino acid sequence by mutations in the DNA that encodes the protein of interest. Of the choices given, only site-directed mutagenesis affects the primary structure.

Amino acid catabolism releases nitrogen in the form of ammonia. In the liver, the urea cycle prepares ammonia for excretion. Which amino acid could undergo deamidation to produce ammonia for the urea cycle? A.Glutamine B.Arginine C.Glycine D.Aspartate

A.Glutamine Amino acids all have a common backbone structure that consists of an amino group bonded to a carbon atom (the α-carbon), which is bonded to a carboxylic acid. The α-carbon is also bonded to a side chain, called an R-group, which gives the amino acid its identity. Amino acid catabolism (degradation) involves the removal of nitrogen from backbones and certain R-groups in the form of ammonia, which is detoxified and prepared for excretion by the urea cycle: The nitrogen of amino acid backbones is removed by transamination and deamination (removal of an amine to produce a ketone), producing α-keto acids in the process. The side chains of asparagine and glutamine contain amides, which are catabolized by deamidation rather than deamination. Deamidation releases ammonia from an amide instead of an amine, producing a carboxylic acid instead of a ketone. Of the choices given, only glutamine can produce ammonia through deamidation.

Action potentials move (faster or slower) in myelinated segments of the neuron?

Action potentials move faster in myelinated segments because the capacitance of the membrane is reduced. This decreases the number of ions and the time needed to change the membrane potential in these areas. -Capacitance (in this context) = total number of charges along the membrane, or number of ions that can be stored in the layers on both sides of the membrane at any given potential (because potential represents strength of the charge separation for any particular ion carrier). -The closer charges are to each other, the more charge can be stored.

Is ammonia (NH3) a weak or a strong base?

Ammonia (NH3) is a weak base

What converts angiotensin I to angiotensin II?

Angiotensin converting enzyme (ACE)

antigen vs antibody

Antigens are molecules capable of stimulating an immune response. Each antigen has distinct surface features, or epitopes, resulting in specific responses. Antibodies (immunoglobins) are Y-shaped proteins produced by B cells of the immune system in response to exposure to antigens. Each antibody contains a paratope which recognizes a specific epitope on an antigen, acting like a lock and key binding mechanism. This binding helps to eliminate antigens from the body, either by direct neutralization or by 'tagging' for other arms of the immune system.

Missense mutation:

Any genetic mutation that changes an amino acid from one to another. 2 types: • Conservative mutation: new AA is the same type as the original (ex: Glu —> Asp, both are acidic) • Non-conservative mutation: new AA is different type than the original (ex: Ser (polar)—> Phe (non-polar, aromatic))

Non-sense mutation:

Any genetic mutation that leads to RNA sequence codon being a stop codon This affects resulting protein more than missense mutations, may cut off a lot of AA residues

What is an antigen?

Anything that causes an immune response. Can be entire pathogens, like bacteria, viruses, fungi, and parasites; or smaller proteins that pathogens express. Antigens are like a name tag for each pathogen that announce the pathogens' presence to your immune system. Some pathogens are general, whereas others are very specific. A general antigen would announce "I'm dangerous", whereas a specific antigen would announce "I'm a bacteria that will cause an infection in your gastrointestinal tract" or "I'm the influenza virus".

Archaea have what type of chromosome?

Archaea have circular chromosomes. Organisms classified under Archaea share traits with bacteria. Like bacteria, archaea are unicellular (single-celled), have a circular chromosome, have no membrane-bound organelles or nucleus, and reproduce asexually via binary fission. However, unlike bacteria, archaea do not have the chemical peptidoglycan in their cell wall

small nuclear RNA (snRNA)

Avg. length is ~150 nucleotides. Primary function is in processing of pre-mRNA in the nucleus. They also aid in regulation of transcription factors or RNA polymerase II, and maintaining telomeres.

Axons with a __________ diameter offers less resistance to ions moving down the axon (more pathways through the cytoplasmic around other cell structures), and therefore allows action potential to be conducted faster (because speed of action potential is related to speed of ions moving down axon).

Axons with a larger diameter offers less resistance to ions moving down the axon (more pathways through the cytoplasmic around other cell structures), and therefore allows action potential to be conducted faster (because speed of action potential is related to speed of ions moving down axon).

Under physiological conditions, peptide bond formation and degradation both require enzymes, but only formation requires coupling to GTP hydrolysis. Based on this information, peptide bonds under physiological conditions are: A.both thermodynamically and kinetically stable. B.thermodynamically unstable but kinetically stable. C.thermodynamically stable but kinetically unstable. D.both thermodynamically and kinetically unstable.

B.thermodynamically unstable but kinetically stable. Chemical reactions, including those in biological settings, are controlled both by thermodynamics and kinetics. Thermodynamics describes the energy difference between products and reactants (ΔG), and dictates whether a reaction requires energy input. Kinetics describes the energy required to initiate a reaction (activation energy), and determines how quickly a reaction proceeds. If a reaction has a positive ΔG (as in anabolic processes such as protein synthesis), the product is thermodynamically unstable and the reaction requires energy input. In biological settings, this energy input is usually derived from the hydrolysis of ATP or GTP. The reverse reaction is thermodynamically favorable (negative ΔG) and requires no energy input; however, this does not mean the reverse reaction will proceed quickly. Reactions that are thermodynamically favorable but have high activation energies are slow, and the bonds that are broken in these reactions are said to be kinetically stable. The question states that peptide bond formation requires coupling to GTP hydrolysis, a source of energy. Therefore, formation requires energy input and degradation does not, indicating that peptide bonds are thermodynamically unstable (ie, prone to breaking). However, the question also states that degradation requires enzymes. Enzymes increase the rate of otherwise slow reactions by decreasing the activation energy, so in the absence of enzymes peptide bonds degrade slowly, making them kinetically stable.

Because axons with a (smaller or larger) diameter and a (thinner or thicker) myelin sheath conduct action potentials more rapidly, the somatosensory neurons for position, vibration and some touch will conduct action potential much faster than the others.

Because axons with a larger diameter and a thicker myelin sheath conduct action potentials more rapidly, the somatosensory neurons for position, vibration and some touch will conduct action potential much faster than the others.

Which of the three muscle cell types can be striated? -Smooth -Cardiac -Skeletal

Both cardiac and skeletal muscle cells can be striated. The only muscle cell that CANNOT be striated is the smooth muscle cell

The pKa for the side chain of cysteine is 8.4. What is the ratio of protonated side chain (-SH) to deprotonated side chain (-S−) in a solution of cysteine at physiological pH of 7.4? A.1:100 B.1:10 C.10:1 D.100:1

C. 10:1 Some chemical groups, including the side chains of some amino acids, can be protonated or deprotonated depending on the pH of the surrounding environment. The pKa of a chemical group is the pH at which the ratio of protonated to deprotonated species is 1:1. A decrease in pH yields increased H+ concentration (favors protonation) whereas an increase in pH yields decreased H+ concentration (favors deprotonation). The protonated:deprotonated ratio of a substance can be determined by solving the Henderson-Hasselbalch equation. However, when the pH differs from the pKa by an integer number of pH units, the ratio can be determined more easily because each pH unit alters the ratio by a factor of 10. The question states that the pKa of the cysteine side chain is 8.4 and the solution is at a pH of 7.4. Because the pH of the solution is lower than the pKa of cysteine, the protonated form of cysteine will be favored. Furthermore, because the pH is exactly 1 pH unit lower than the pKa, protonated cysteine will exceed the deprotonated form by a factor of 10. Therefore, the ratio of protonated to deprotonated cysteine side chain at physiological pH is 10:1.

Compared with blood in the pulmonary veins, blood in the pulmonary arteries has higher concentrations of: I O2 II H+ III CO2 A.I and II only B.I and III only C.II and III only D.I, II, and III

C. II and III only Blood is circulated throughout the body by the repetitive contraction of the heart, which enables continuous delivery of oxygen and nutrients to the body's tissues, as well as removal of CO2 (the major metabolic by-product of cellular respiration) and other waste products. The blood vessels involved in circulation can be divided into two circuits: The systemic circuit distributes oxygenated blood (high O2, low CO2, low H+) containing nutrients to all body tissues via arteries, which carry blood away from the heart. When oxygenated blood reaches the capillaries within the systemic tissues, it delivers O2 (becomes deoxygenated) and nutrients to the tissues and picks up CO2. Veins then return the deoxygenated blood (low O2, high CO2, high H+) back to the heart so that it can enter the pulmonary circuit. The pulmonary circuit pumps deoxygenated blood through the pulmonary arteries to capillaries in the lungs to facilitate gas exchange. The capillaries are in close contact with lung alveoli (air sacs), and at this site, the blood becomes reoxygenated (O2 is transferred from alveolar air to the blood, and CO2 is transferred from the blood to the alveolar air). The pulmonary veins then return the oxygenated blood to the heart so that it can be pumped through the systemic circuit (Number I). Compared with oxygenated blood in the pulmonary veins, deoxygenated blood in the pulmonary arteries has higher concentrations of CO2 (Number III). Blood that is richer in CO2 is also generally richer in H+ ions due to the following reaction that takes place in red blood cells: CO2(g)+H2O(l)↔H2CO3(aq)↔HCO3−(aq)+H+(aq)CO2g+H2Ol↔H2CO3aq↔HCO3-aq+H+aq The higher the CO2 concentration, the more the forward reaction is favored. Therefore, the CO2-rich blood in the pulmonary arteries also contains more H+ ions (has a slightly lower pH) than the CO2-poor blood of the pulmonary veins

Scientists could confirm that an allosteric effector increases the catalytic efficiency of an enzyme if it has what effect on kcat and Km? A.kcat decreases, Km increases B.kcat decreases, Km remains unchanged C.kcat increases, Km decreases D.kcat remains unchanged, Km increases

C.kcat increases, Km decreases Catalytic efficiency is a measure of how well an enzyme facilitates reactions at low substrate concentrations. When enzyme concentration is held constant, catalytic efficiency is proportional to the initial slope of a Michaelis-Menten curve (when [S] << Km). This slope is governed by both the catalytic turnover kcat and the Michaelis constant Km. Mathematically, catalytic efficiency is calculated as the ratio of kcat to Km. An increase in kcat increases the catalytic efficiency, and a decrease in Km also increases the efficiency. Therefore, an allosteric activator that both increases kcat and decreases Km will increase the catalytic efficiency of an enzyme. Conceptually, a large (steep) slope indicates an efficient enzyme because a small amount of substrate yields a high reaction rate. Catalytic turnover (kcat) measures the number of substrate molecules converted to product per enzyme per second when the enzyme is saturated; therefore, a high kcat corresponds to a high maximum rate (Vmax) and, by extension, a larger slope at lower substrate concentrations. The Michaelis constant (Km) is an indicator of binding affinity. A small Km indicates high affinity, allowing the reaction to approach Vmax more rapidly (higher slope) with smaller amounts of substrate. Therefore, a small Km contributes to high catalytic efficiency.

Acetylation of lysine residues in histones increases gene expression because: A.DNA is tightly bound to negatively charged amino acids on histones. B.the carboxyl oxygen atoms in acetyl groups form hydrogen bonds with nitrogenous bases. C.the salt bridges between charged amino acids and phosphate groups are disrupted. D.lysine residues in histones associate with positively charged phosphate groups in DNA.

C.the salt bridges between charged amino acids and phosphate groups are disrupted. DNA is predominantly negatively charged due to the phosphate groups on the backbone. Histones associate with DNA by forming salt bridges between positively charged amino acid residues and negatively charged phosphate groups. These ionic interactions allow histones to bind tightly to DNA and prevent genes from being transcribed. Acetylation of histones involves the transfer of acetyl groups from acetyl coenzyme A to positively charged amino groups on lysine or arginine residues. This modification disrupts salt bridges by reducing the positive charge on histones, which allows DNA to unwind and become more accessible to transcription machinery. As a result, the acetylation of histones causes nucleosomes to relax and increases gene expression.

What is the role of calcitonin?

Calcitonin decreases the amount of calcium and phosphate in the blood. (calcitonin tones down blood)

What type of muscle cell is branched?

Cardiac muscle cells are often branched and can have 1 or 2 nuclei.

Cardiac muscle is unique in that each cell is connected to adjacent cells via __________________, which are regions of cell contact that contain both desmosomes and gap junctions.

Cardiac muscle is unique in that each cell is connected to adjacent cells via intercalated discs, which are regions of cell contact that contain both desmosomes (to prevent cells from separating during contraction) and gap junctions (to facilitate direct ion exchange for synchronized contraction).

_______________ has a rate of urinary excretion that is almost always identical to its rate of glomerular filtration in a healthy adult.

Creatinine has a rate of urinary excretion that is almost always identical to its rate of glomerular filtration in a healthy adult.

A single-stranded DNA oligonucleotide composed of which of the following would move most slowly down an alkaline agarose gel during electrophoresis? A.Deoxyadenosine monophosphate B.Deoxythymidine monophosphate C.Deoxycytidine monophosphate D.Deoxyguanosine monophosphate

D. Deoxyguanosine monophosphate Gel electrophoresis separates molecules by molecular weight, with larger molecules migrating more slowly than smaller molecules. DNA is composed of the four deoxyribonucleotides (dNMPs), each of which has a different molecular weight. The purine deoxyguanosine monophosphate (dGMP) is the largest dNMP, followed by deoxyadenosine monophosphate (dAMP), deoxythymidine monophosphate (dTMP), and deoxycytidine monophosphate (dCMP). An oligonucleotide is a short strand of DNA, and its molecular weight is determined by its composition of dNMPs. An oligonucleotide composed entirely of dGMP will be larger than any other oligonucleotide of the same length and therefore would move the most slowly through an agarose gel.

Which of the following helps maintain the resting membrane potential of a neuron? Passive transport Adenosine triphosphate Membrane selective permeability A.II only B.III only C.I and III only D.I, II, and III

D. I, II, and III The unequal concentration of charged ions between the extracellular and intracellular fluid of all living cells results in an electrochemical gradient across the membrane that determines the membrane potential (voltage difference). The resting membrane potential of neurons is primarily due to the high concentration of potassium ions (K+) and the low concentration of sodium ions (Na+) inside the cell as compared to the outside. The following mechanisms contribute to maintenance of the resting membrane potential: Protein channels in the cell membrane enable certain ions to move down their concentration gradient across the membrane. For example, in resting neurons, potassium leak channels help maintain the membrane potential by enabling the passive transport (without using energy) of K+ out of the cell. Because the membrane is more permeable to K+ than to Na+ (ie, selective permeability), the resting membrane potential of neurons is approximately −70 mV, which is close to the negative equilibrium potential of K+ (Numbers I and III). Active transport pumps embedded in the outer membrane of neurons hydrolyze adenosine triphosphate (ATP) to provide energy to transport molecules against their concentration gradient. For example, sodium-potassium pumps (Na+K+ ATPase) transport 2 K+ into the cell for every 3 Na+ moved out of the cell. This is important for maintaining the unequal concentration of ions across the membrane; without active transport pumps, leakage of ions through the cell membrane would eventually result in equilibration and a membrane potential of 0 mV (Number II).

In order to transport long-chain fatty acids from the cytosol to the mitochondria, three of the following molecules are required. Which one is NOT necessary? A.Coenzyme A B.ATP C.Carnitine D.Oxaloacetate

D. Oxaloacetate Entry into the mitochondrial matrix is tightly regulated by the inner mitochondrial membrane. Crossing the membrane generally requires the aid of transport proteins, which only recognize specific molecules. Some short-chain fatty acids can cross the inner mitochondrial membrane directly, but long-chain fatty acids can only cross the outer mitochondrial membrane. Additionally, long-chain fatty acids are not recognized by any transport proteins; they must be modified or "activated" to enter the matrix. Fatty acid activation and transport includes the following steps: In the cytosol, the enzyme acyl-CoA synthetase catalyzes the reaction of fatty acids with coenzyme A to form acyl-CoA molecules. This reaction is thermodynamically unfavorable and requires ATP hydrolysis to proceed (Choices A and B). Acyl-CoA molecules then migrate to the intermembrane space, where they can react with carnitine to form acylcarnitine. The transport protein acylcarnitine translocase, located on the inner mitochondrial membrane, recognizes acylcarnitine and carries it into the mitochondrial matrix (Choice C). Acylcarnitine is then converted back to acyl-CoA and carnitine. Acyl-CoA is subsequently digested by β-oxidation, and carnitine is transported out of the matrix where it can pick up and carry a new fatty acid into the mitochondrial matrix. Although oxaloacetate is an intermediate in the citric acid cycle, gluconeogenesis, and transport of acetyl-CoA from the mitochondria into the cytosol for fatty acid synthesis, it is not involved in transport of fatty acids from the cytosol into the mitochondria.

Phospholipases release arachidonic acid from cell membranes as part of the inflammatory response. Given this information, which type of molecule is derived from arachidonic acid and is involved in this response? A.Terpenes B.Ketone bodies C.Catecholamines D.Prostaglandins

D.Prostaglandins Localized inflammatory responses occur near the site of an injury or infection. They frequently involve phospholipase enzymes releasing arachidonic acid from the plasma membranes of affected cells. Arachidonic acid is then modified by cyclooxygenase and a series of other enzymes to form various 20-carbon (eicosanoid), nonhydrolyzable lipids known as prostaglandins. Prostaglandins act as autocrine and paracrine signals (binding to receptors on or near the cell from which they originated). Because they act only on nearby cells, prostaglandins produce a localized inflammatory response. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen treat inflammation by inhibiting prostaglandin synthesis.

Fertilization normally occurs in the ________________

Fertilization normally occurs in the uterine tube.

For muscle contraction to occur, there must be a _________ concentration of Calcium ions

For muscle contraction to occur, there must be a high concentration of Calcium ions. The sarcoplasm reticulum is responsible for controlling the amount of calcium present, using ATP to release calcium ions when a muscle contraction is needed.

microRNA (miRNA) and small interfering RNA (siRNA)

Functions in transcriptional and post-transcriptional regulation of gene expression by base pairing with complementary sequences within mRNA molecules. This usually results in gene silencing. The mRNAs to which miRNAs bind are prevented from translation or sent through a pathway for degradation.

Gram-__________ bacteria are more likely to cause systemic effects because their outer membrane protects them from several antibiotics, making treatment more difficult.

Gram-negative bacteria are more likely to cause systemic effects because their outer membrane protects them from several antibiotics, making treatment more difficult.

Is H < 0 endothermic or exothermic?

H < 0 is exothermic

Is H > 0 endothermic or exothermic?

H > 0 is endothermic

_________________ canals travel through bone tissue and allow for innervation and vascularization of bone. This is the most direct way the medication would reach bone tissue.

Haversian canals travel through bone tissue and allow for innervation and vascularization of bone. This is the most direct way the medication would reach bone tissue.

Is hydrochloric acid (HCl) is a weak or a strong acid?

Hydrochloric acid (HCl) is a strong acid

Describe beta-oxidation for a carbon chain with an odd number of carbons:

If the fatty acid has an odd number of carbons, the final three carbons are converted into a compound called propionyl-CoA. In other words, for odd-chain fatty acids, the number of acetyl-CoA units produced equals (total carbons − 3)/2. Fatty acids are long hydrocarbon chains with a carboxylic acid group on one end. They are degraded through a process called fatty acid oxidation, or β-oxidation, which proceeds differently depending on the composition of the fatty acid being oxidized. All fatty acids are broken down into multiple two-carbon units called acetyl-CoA. Fatty acids with an even number of carbons yield half as many acetyl-CoA units as the total number of carbons in the original molecule. Unsaturated fatty acids have at least one C=C double bond, typically in the cis-conformation. For β-oxidation to proceed, the cis-bonds must be isomerized to trans-bonds, which are introduced as part of the oxidation mechanism. Saturated fatty acids do not have C=C double bonds initially and do not need to undergo isomerization during β-oxidation.

During muscle contraction, do the A-bands or the I-bands shorten? Which one stays the same length?

In contraction, it's the actin filaments that move. So the Z-lines move closer together, towards the center of the sarcomere, and the I band is shortened but the A-band remains the same length.

What is the largest organ in the body?

Integument (skin and its derivatives)

Lactose is made up of:

Lactose is a sugar molecule that is made up of two smaller sugars, glucose and galactose.

What is the cofactor for the pyruvate dehydrogenase complex (PDHC)?

Lipoic acid. The pyruvate dehydrogenase complex (PDHC) is an enzyme composed of three subunits (E1, E2, and E3). It catalyzes the oxidative decarboxylation of pyruvate to form acetyl-CoA, along with the reduction of NAD+ to form NADH. During this process, electrons are passed from one subunit in the complex to the next until they can be transferred to NAD+. This transfer is facilitated in part by the cofactor lipoic acid.

Describe a lyase:

Lyases either form two molecules by breaking a bond within one molecule or they combine two molecules into one. To form bonds between reactant molecules, lyases add groups to a double bond. In the reverse reaction, they break a single bond in a reactant and generate a new double bond in the products. Ex) Aldolase splits F1,6BP into glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP) by forming a new C=O double bond. Therefore, aldolase is a lyase.

Mitochondria are found in higher numbers in what muscle type?

Mitochondria are more prevalent in type 1 muscle than type 2

Describe the stages of muscle contraction:

Muscle contraction is dependent on the interaction between the myosin (thick) and actin (thin) protein filaments in the sarcomere, the basic contractile unit of muscle tissue. To generate muscle contraction, the sarcomere functions as follows: When the muscle fiber is at rest, the myosin head is in its high-energy conformation (upright and bound to ADP and Pi), and the actin filaments are bound by the regulatory proteins tropomyosin and troponin. Tropomyosin is an elongated protein that wraps around the actin filament to block myosin-binding sites on this thin filament. Troponin is a small protein complex associated with tropomyosin. Following a depolarizing stimulus by a motor neuron, Ca2+ ions are released from the sarcoplasmic reticulum into the cytosol. The abundant cytosolic Ca2+ ions bind troponin, causing a conformational change that ultimately pulls on tropomyosin and exposes the myosin binding sites on the actin filaments. When the active sites are exposed, the myosin head is able to bind strongly to the actin filament, forming a cross-bridge and promoting the release of ADP and Pi. The dissociation of ADP and Pi causes the power stroke, which is the actual pivot of the actin-bound myosin head that drags the actin filament toward the center of the sarcomere. This directly results in shortening of the sarcomere. The myosin head is now in its low-energy conformation. A new ATP molecule binds the myosin head and the cross-bridge disassembles. Hydrolysis of the ATP molecule allows the myosin head to shift back into its upright, high-energy conformation in preparation for a new cycle of contraction. The cycle of cross-bridge formation and disassembly continues until motor neuron signaling ceases, and Ca2+ is sequestered back into the sarcoplasmic reticulum.

Muscle type 1 is _______ twitch. Muscle type 2 is ______ twitch

Muscle type 1 is slow twitch. Muscle type 2 is fast twitch

Do mutations arise at the transcription or translation level?

Mutations ONLY arise during transcription, but the result of the mutations are seen and expressed at the protein level (transcription)

Frame shift mutation:

One DNA base is added to the gene sequence. This leads to an additional base in the mRNA sequence, which changes the reading frame (codons) of the mRNA during translation. All codons (and corresponding AA) that come after the extra base will be slightly different. Frame-shift mutations have a more significant effect on final protein than point mutations Note: point mutation and frame shift mutations are classified by their effects on DNA.

What are the roles of osteoblast and osteoclast?

Osteoblasts build bone, and form osteoids osteoclasts crush bone (break it down). Osteoclasts reabsorb the components of bone.

What is the role of the parathyroid hormone (PTH) and calcitrol?

Parathyroid hormone (PTH) and calcitrol both increase calcium in the blood; but PTH decreases phosphate levels, while calcitrol increases them.

What type of macromolecule does pepsin degrade?

Pepsin only degrades protein. Pepsin is found in the stomach where only protein is broken down.

Are phosphatases or phosphokinases used in gluconeogenesis?

Phosphatases are used because they have to remove a phosphate in the step in order to reverse the sign

_____________ cation is found in greatest concentration inside a neuron.

Potassium cation is found in greatest concentration inside a neuron.

____________ produce myelin sheath in the PNS

Schwann cells

In gel electrophoresis, do smaller or larger objects move faster?

Smaller objects move faster because they are carrying less mass. (They move from the negative charge to the positive charge)

Influx of what ion into the axon terminal body, is responsible for the release of acetylcholine?

The Ca2+ then binds to vesicles that are holding neurotransmitter, acetylcholine the vesicles bind to the membrane of the neuron, and lots of acetylcholine is released into the synaptic cleft.

DNA methylation

The addition of methyl groups (—CH3) to bases of DNA after DNA synthesis; may serve as a long-term control of gene expression or gene inactivation.

Point mutations are:

The addition or loss of a nucleotide as well as substitution of one, and thus a change in one amino acid. Two types are transition (one purine for another (vice versa for pyrimidines) and transversion ( purine for pyrimidine) .

Suppose a nanotechnological innovation allows every single charged ion to be precisely identified and removed from a small volume of water. Which of the following describes K_aKa​K, start subscript, a, end subscript for the water at the end of the process, assuming that the filtered water is given adequate time to re-equilibrate?

The autoionization of water occurs naturally due to attractive forces between constituents of water molecules. -Even if all ions are removed from a sample of water (including hydronium ions), a short time later the water will re-ionize until it approaches an equilibrium concentration of ions. In equllibrium, Ka = Kw = 10^{-14}

The influx of what ion is responsible for depolarization?

The change in charge typically occurs due to an influx of sodium ions into a cell, although it can be mediated by an influx of any kind of cation or efflux of any kind of anion.

Describe the role of endothelium cells:

The endothelium is the one-cell-thick layer of specialized epithelial cells (ie, endothelial cells) that line the interior of the cardiovascular system, which includes the heart, arteries, capillaries, and veins. The endothelium, which is in direct contact with the blood in the lumen (inner cavity), is a relatively smooth, friction-reducing surface that enables the efficient movement of blood through the vasculature. The endothelium also acts as a barrier that regulates the exchange of substances between the blood and nearby tissues. For example, in response to inflammatory chemicals released during an infection, endothelial cells promote the movement of white blood cells out of the bloodstream to the affected tissue.

Describe the main roles of the liver:

The liver is located in the upper right side of the abdominal cavity, just below the diaphragm, and performs various functions within the body. According to the question, cirrhosis causes hepatic cell death and scarring. As a result, the following normal functions of the liver are severely impacted: Ketogenesis: Ketogenesis (synthesis of ketone bodies) occurs mainly in the liver and plays a critical role in energy metabolism when glycogen stores are depleted and blood glucose levels become low. During times of fasting, mitochondria within liver cells convert acetyl coenzyme A into ketone bodies, which are then used by the brain to make ATP. Detoxification of drugs: Drugs are often exogenous compounds that may have toxic effects if allowed to accumulate in the body. The liver is a critical organ for the breakdown and detoxification of many drugs. Synthesis of plasma proteins: Osmotic pressure within capillaries is due to the presence of plasma proteins that cannot easily cross the capillary membrane. Oncotic pressure causes a "pulling force" inside capillaries, which balances the pushing force of hydrostatic pressure, helping keep fluid in the vasculature. The majority of plasma proteins such as albumin are synthesized in the liver. Therefore, cirrhosis is expected to impact the production of plasma proteins, which in turn would affect oncotic pressure in the capillaries

In the small intestine, where does most of the digestion take place? Where does most of the absorption take place?

The majority of the digestion in the small intestines takes place in the duodenum and the majority of the absorption in the small intestines takes place in the jejunum

Describe the synthesis and secretion of pituitary hormones:

The pituitary gland is a small structure that sits inside a bony cavity below the hypothalamus at the base of the brain. It is attached to the hypothalamus via the pituitary stalk and can be divided into two separate lobes: The anterior lobe is made up of glandular tissue that synthesizes and secretes follicle-stimulating hormone (FSH), luteinizing hormone (LH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), growth hormone (GH), β-endorphins, and prolactin. The synthesis and secretion of hormones from the anterior pituitary is controlled primarily by neurohormones released from hypothalamic neurons. These regulatory neurohormones are secreted into the hypophyseal portal system, a network of small blood vessels that enables small quantities of hormones secreted from the hypothalamus to directly reach the anterior pituitary without being diluted in the circulation. The posterior lobe, made up of axonal projections from the hypothalamus, stores and secretes the hormones oxytocin and vasopressin (also called antidiuretic hormone [ADH]). Posterior pituitary hormones are synthesized in hypothalamic neurons and then transported down the axon to the axon terminals in the posterior pituitary, where they are stored. The secretion of stored hormones from the posterior pituitary is mediated by action potentials that cause exocytosis of neurosecretory vesicles.

How does the activation energy (Ea), effect the speed/rate of the reaction?

The smaller/lower the activation energy (Ea), the faster the reaction will proceed. Remember that enzymes work by lowering the activation energy (Ea) but does not change if the reaction is thermodynamically possible (does not change delta G) *The red arrow is the Ea

The three main hormones responsible for maintaining calcium homeostasis are:

The three main hormones responsible for maintaining calcium homeostasis are: 1) Parathyroid (PTH) 2) Calcitonin 3) Calcitriol (which is basically the active form of vitamin D).

What are effector cells?

These turn into antibody factories; they start spitting out tons and tons of the variable proteins that can uniquely bind to the infecting pathogens.

What type(s) of cells do you obtain after a F+ bacterium conjugates with a F- bacterium?

Two F+ bacteria with identical plasmid but not chromosomal DNA

Describe type 1 muscle fibers:

Type 1 fibers are fatigue-resistant, contract slowly, and use aerobic respiration as their primary method of ATP production. Consequently, compared with glycolytic fibers, type 1 fibers are much richer in mitochondria, the site where many enzymes involved in aerobic respiration reside. Type 1 fibers also have access to a continuous supply of oxygen (the final electron acceptor of aerobic respiration) through an extensive network of capillaries that surround the muscle. In addition, type 1 fibers appear red under the microscope due to high concentrations of myoglobin, a red-pigmented, oxygen-binding molecule that delivers oxygen to the muscle cell interior, where the mitochondria are housed.

The acetylation of histones:

Unwinds DNA (opens chromatin), adds actyl group- changes shape = genes turned ON

does angiotensin II cause acidosis or alkalosis?

alkalosis - stimulates Na+/H+ exchange in proximal tubule, so H+ is excreted. Na+ is reabsorbed

What is a cytokine?

any of a number of substances, such as interferon, interleukin, and growth factors, that are secreted by certain cells of the immune system and have an effect on other cells.

Tendons

attach muscle to bone

Opsonization

coating antigen with antibody enhances phagocytosis

proximal convoluted tubule (PCT)

first section of the renal tubule that the blood flows through; reabsorption of water, ions, and all organic nutrients.

Bile is produced by

hepatocytes in the liver

Angiotensin II

increases blood pressure by stimulating kidneys to reabsorb more water and by releasing aldosterone

__________ attach bone to bone

ligaments attach bone to bone

In the CNS, the myelin sheath is produced by

oligodendrocytes

___________ produce myelin sheath in CNS

oligodendrocytes

Which of the following describes the pH of an equilibrated, stoichiometric mixture of ammonia, (NH3) and hydrochloric acid (HCl)? pH > 7 pH = 7 pH < 7 pH = 4

pH < 7 -Ammonia is a weak base -Hydrochloric acid is a strong acid -The hydrochloric acid will donate a proton to the ammonia to form ammonium, NH4+ superscript -Ammonium reacts with water to form hydronium, NH4+​+H2​O→NH3​+H3​O+ -A mixture of a strong acid and a weak base acquires an overall acidic pH < 7

ascending loop of henle

reabsorbs Na+ and Cl- from the filtrate into the interstitial fluid using active energy. Water cannot be reabsorbed here

descending loop of henle

reabsorption of water through passive diffusion. It is impermeable to any ions and ions cannot be reabsorbed here.

What converts angiotensinogen to angiotensin I?

renin from the kidneys

In the PNS, the myelin sheath is produced by

schwann cells.

actin is composed of

thin filaments

For muscle contraction to occur

tropomyosin must be moved away from the myosin-binding sites so that actin and myosin can interact.

Ca+ binds to what? (sliding muscle filament theory)

troponin