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MCAT Biology Flashcards

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1
Q

How do enzymes affect reactions?

A

The catalytic action of enzymes changes the activation energy, and thus the reaction rate. Enzymes decrease the activation energy. Enzymes DO NOT alter equilibrium constant, equilibrium concentrations, nor spontaneity.

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2
Q

How would being in a hot dry climate keep one cooler than in a place of high humidity?

A

Sweating in hot dry place occurs more easily. Evaporation of liquid dissipates body heat helping to lower the body’s temperature and keep it from overheating. In a dry climate, the low humidity allows water to evaporate more easily, increasing sweating.

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3
Q

What type of protein (category and specific name(s)) form skin, hair, and nails. (just name them)

A

Fibrous proteins - keratins

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4
Q

What are characteristics of keratins

A

They are fibrous proteins that are classified as soft or hard according to their sulfur content (i.e. the relative number of cysteine residues in their polypeptide chains). The low-sulfur keratins of the skin are much more flexible that the high-S, hard keratins

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5
Q

Name the kind of proteins make up muscles (category and specific name(s))

A

Fibrous proteins - actin and myosin

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6
Q

What is the role of actin and myosin proteins and how do their work?

A

Actin and myosin proteins of muscle tissue interact to form cross-linkages that allow the sliding of the filaments over each other in muscle contraction, which takes place through the contraction and relaxation of the sarcomere, the fundamental unit of all muscle fibers. When the muscle contracts, the actin and myosin filament slide over each other and the H-zone (actin-only region), Z-lines (sarcomere boundries), and I-ban (myosin-only region) all shrink, while the A-band (the entire myosin region) remains the same size. The opposite occurs upon muscle relaxation

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7
Q

What is the fundamental unit of all muscle fibers?

A

Sarcomere

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8
Q

What is a Z-line

A

A sarcomere boundary in muscle tissue upon which the actin and myosin filaments slide over

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9
Q

What is the H-zone

A

The actin-only region in muscle tissue upon which the actin and myosin filaments slide over

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10
Q

What is the I-band

A

The myosin-only region in muscle tissue upon which the actin and myosin filaments slide over

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11
Q

Name the kind of protein found in tendons and connective ligaments within the body (category and specific name(s))

A

Fibrous proteins - collagen

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12
Q

Name three different fibrous proteins

A
  • Keratin (hair, skin, nails)
  • Myosin and actin (muscle tissue)
  • Collagen (connective tissue)
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13
Q

What is collagen

A

A type of fibrous protein (structural protein). It is a triple helix formed by three proteins that wrap around one another. Many collagen molecules are cross-linked together in the extracellular space to form collagen fibrils to provide structural support for the cell. Elastin polypeptide chains are cross-linked together to form flexible, elastic fibers that give stretched tissues flexibility and the ability to recoil spontaneously as soon as the stretching force is relaxed.

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14
Q

What is a peptide?

A

A peptide is an amide linkage between the amine group of one amino acid and carboxylic acid group of another.

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15
Q

What is a peptide?

A

A peptide is an amide linkage between the amine group of one amino acid and carboxylic acid group of another.

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16
Q

Why are peptides stable?

A

A peptide is an amide linkage between the amine group of one amino acid and carboxylic acid group of another. Amides are stable because they exhibit resonance stabilization between the lone pair on the nitrogen and the double-bond in the carbonyl group

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17
Q

What is physiological pH?

A

7.4

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18
Q

What happens to a typical protein at physiological pH (charges)?

A

-1 charge on deprotonated carboxylic acid terminal and a +1 charge on its protonated amino acid amino terminal for a total 0 net charge from its termini.

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19
Q

In general what kind of amino acids have the potential to become positively charged at physiological pH?

A

Basic amino acids (cationic side chain)

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20
Q

In general what kind of amino acids have the potential to become negatively charged at physiological pH?

A

Acidic amino acids (anionic side chain)

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21
Q

Inflammatory response, which is marked by increased vasolidation, blood vessel permeability, and paint is classified as what?

A

A function of the innate immune system

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22
Q

What is the innate immune system?

A

The innate immune system includes nonspecific immune responses. In other words, its responses provide general protection rather than protection against specific pathogens that have been previously encountered and “remembered.” Inflammation is a function of the innate immune system, as it serves as a general response to infection or injury.

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23
Q

What is adaptive immunity?

A

Adaptive immunity is directed against particular pathogens to which the body had been previously exposed. These pathogens are “remembered” by specialized cells, leading to a quicker response in the case of a second exposure.

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24
Q

What is passive immunity?

A

Passive immunity involves the transfer of antibodies from one individual to another.

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25
Q

In eukaryotes, which residues are most prone to phosphorylation?

A

Serine (S), tyrosine (Y), threonine (T)

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26
Q

What is the function of aldosterone and where/why is it released from?

A

Aldesterone is released from the adrenal cortex in response to low blood pressure. Its primary funciton is to increase sodium reabsoprtion in the distal tubule and coelcting duct. Aldosterone upregulates the sodium-potassium pumps along the lining of the nephron, pumping three sodium ions OUT of the nephron lining (and toward the blood) for every two potassium ions it pumps IN (toward the nephron and away from the blood).

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27
Q

What process is responsible for cell culture growth and for maintaining genetic integrity between parent cells and daughter cells within a cell culture

A

Mitosis

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28
Q

Is meiosis cyclical? Is mitosis cylical?

A

Meiosis in noncyclical and terminates in gamete creation (either sperm cells or ova). It happens once. Mitosis is a cyclical process

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29
Q

What process includes genetic recombination in order to create genetic diversity in offspring?

A

Meiosis

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30
Q

What aspects separate single-crossover events from double-crossover events?

A

Single-crossover events affect only the ends of chromosome arms, while double-crossover events can affect segments in the middle of chromosome arms

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31
Q

Which tissues utilize troponin

A

Skeletal muscle and cardiac muscle

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32
Q

How are the cells of cardiac muscle connected?

A

Gap junctions (intercalated discs that connect the cytoplasm of adjacent cardiac muscle cells, allowing ions to pass from cell to cell)

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33
Q

Which tissues are striated

A

Cardiac muscle and smooth muscle

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34
Q

Skeletal muscle is innervated by what? (think type of control)

A

Somatic nervous system, meaning conscious control

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35
Q

Smooth muscle is innervated by what? (think type of control)

A

Autonomic nervous system, meaning not voluntary control

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36
Q

What are red fibers and what are their functions?

A

Red fibers (slow-twitch fibers) are a type of skeletal muscle. They obtain their color from the presence of abundant reserves of myoglobin, and are also rich in mitochondria. This means that they prefer oxidative metabolism, and therefore are present in large quanitities in muscles that specialize in performing less intense actions over a longer period of time

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37
Q

What are white fibers and what are their functions?

A

White fibers (fast-twitch fibers) lack myoglobin and mitochondria and tend to mobilize glycogen for quick bursts of intense action followed by fatigue.

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38
Q

How are peptide bonds broken?

A

Hydrolysis

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39
Q

What kind of reaction results in the formation of peptide bonds?

A

Condensation

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40
Q

In what conformation do peptide bonds usually exist?

A

Trans

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41
Q

What is Beta-oxidation (process definition)?

A

Beta-oxidation is a process in which fatty acids are broken down into acetyl-CoA, which can be fed into the citric acid cycle (Krebs cycle) similar to the effects of glycolysis and the pyruvate dehydrogenation complex. Beta-oxidation also generate the electron carriers NADH and FADH2. The beta carbon of each fatty acid is oxidized to a carbonyl.

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42
Q

How does Beta-oxidation affect the Krebs cycle?

A

In addition to breaking down fatty acids into acetyl-CoA, beta-oxidation also generates electron carriers NADH and FADH2 which produce energy in teh electron transport chain. The beta carbon of each fatty acid is oxidized to a carbonyl group. It occurs in the mitochondria in eukaryotic cells.

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43
Q

What is the Hardy-Weinberg equation?

A

The total number of alleles in a population has to add up to 1: A + a = 1
And the total number of genotypes in the population must also add up to 1: AA + 2Aa + aa = 1
For examples, if the frequency of the recesssive autosomal allele for polydactyly is 1.2% then a=.012 and A=.988. Therefore 2Aa = 2 x 0.988 x 0.012

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44
Q

What structure makes up mitotic spindles?

A

Microtubules

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45
Q

What are free radicals and what important role do they play in reactions?

A

Free radicals are molecules or atoms that contain on unpaired valence electron. As such, they typically serve as highly reactive oxidizing agents

46
Q

Are FADH2 and NADH reducing or oxidizing agents?

A

FADH2 is the reduced form of flavin adenine dinucleotide (FAD) and NAD is the reduced for of nicotinamide adenine dinucleotide (NAD). Since they are reduced (and are carrying electrons) they tend to serve as reducing agents and would not oxidize.

47
Q

Are fungi eukaryotes or prokaryotes?

A

Eukaryotes

48
Q

How can amino acids help buffer blood?

A

Amino acids that make up a protein may include many acidic or basic side chain groups. Those side chains can either release or absorb protons, allowing them to help buffer the blood through action as a Bronsted-Lowry acid or base

49
Q

What is reduced but never oxidized in the electron transport chain?

A

Oxygen is reduced to form H2O

50
Q

What is oxidative phosphorylation

A

The finale major process of aerobicrespiration through which the majority of aerobically-derived ATP is synthesized. The process begins by passing electrons through a ETC. The final electron acceptor is oxygen. This is the only time in eukaryotic aerobic respiration where oxygen is directly required. These reactions take place in specialized proteins where the energy from NADH and FADH2 (molecules formed in glycolysis and the Krebs Cycle/citric acid cycle) is used up, molecule oxygen is reduced into water, and approximately 30-36 ATP are created from ADP and inorganic phosphate.

51
Q

What is complex I of ETC?

A

Complex I is known as NADH dehydrogenase

52
Q

What is complex II of ETC?

A

Complex II is known as succinate dehydrogenase

53
Q

What is complex III of ETC?

A

Cytochrome bc or c

54
Q

What is complex IV of ETC?

A

Cytochrome c oxidase

55
Q

How is ATP generated during oxidative phosphorylation?

A

In the ETC, the energy release from the series of electron transfers is used to pump H+ across the membrane. The unequal concentrations of H+ ions across the membrane establishes an electrochemical gradient, leading to chemiosmosis, or the passive diffusion of the protons down their concentration gradient, which is couple to ATP synthase. This proton ovement generates 90% of the ATP syntheiszed during oxidative phosphotylation. The electrons passing through the electron transport chain gradually lose energy until eventually they are donate to O2, which accepts two H+ ions and is transformed into water.

56
Q

What is chemiosmosis?

A

The passive diffusion of protons down their concentration gradients, which is couple to ATP synthase. If proton gradient is disrupted or destroyed, chemiosmosis can become uncouples from the ETC, resulting in little to no ATP generation despite the transfer of electrons carrying on. Many poisons and toxins act by uncoupling the proton gradient from ATP synthase.

57
Q

What is Km?

A

Km is the substrate concentration required to reach Vmax/2

58
Q

What is noncompetitive inhbition and how are Km and Vmax affected?

A

Noncompetitive inhibition is when the inhibitor does not compete with the substrate for the active site, but reduces enzyme activity by binding to another site on the enzyme (allosteric inhibition). Vmax is decreased and Km increases

59
Q

What is competitive inhibition and how are Km and Vmax affected?

A

Competitive inhibition is when the inhibitor directly competes with the substrate for the active site on the enzyme. Km increases since it now takes more substrate to ensure half of the active sites are occupied. Vmax does not change

60
Q

How is Km associated with enzyme substrate affinity?

A

enzyme substrate affinity α 1/Km (higher Km means weaker affinity)

61
Q

What is uncompetitive inhibition and how are Km and Vmax affected?

A

Uncompetitive inhibition is when the inhibitor binds to only the enzyme-substrate complex, and inactivates it. This causes the number of active enzyme-substrate complexes to descrease, thereby decreasing Vmax. Km also decrease to exactly the same degree as Vmax.

62
Q

How is the % yield determined for the synthesis of X amino-acid length peptide (assuming 95% yield for each coupling step)

A

If there is a 95% yield for each couping step and the cycle was run x times, (0.95)^x=final % yield

63
Q

Define lacteals

A

Lacteals are structures in the intestines associated with absorbing fat into the lymphatic system

64
Q

How many chromosome and autosomes do humans have?

A

46 chromosomes, 22 autosomes, and either 2 X chromosomes or one X and one Y chromosome

65
Q

What is resting phase of the cell cycle?

A

interphase. Resting phase is also known as Gap 0 (G0).

66
Q

What is the phase of the cell cycle during which cell division occurs?

A

mitosis or meiosis

67
Q

What happens during interphase? What state is the chromatin?

A

The cell prepares for division. Duing this phase growth and DNA replication occur. There are three stages: Gap 1 (G1), synthesis (S), and Gap 2 (G2). Throughout interphase, chromatin is loosely packaged (euchromatin) to allow transcription and replication.

68
Q

What happens during G1 of cell cycle?

A

The cell grows

69
Q

What happens during G2 of the cell cycle?

A

The cell grows

70
Q

What happens during S of the cell cycle?

A

DNA is replicated. S is located between G1 and G2 and allows checkpoints.

71
Q

Where do checkpoints occur during the cell cycle?

A

G1/S=restriction point, when a cell commits to division. TThe presence of DNA damage or other external factors can cause a cell to fail this checkpoint and not divide. The G2 checkpoint that takes place before cell division similarly checks for DNA damage after DNA replication, and if damage is detected, serves to “pause” cell division until the damage is repaired.

72
Q

What happens after interphase?

A

Cell undergoes division (mitosis in non-sex/germ cells). Mitosis proceeds through prophase (where the nuclear membrane disappears, chromosomes condense, and the mitotic spindle forms), metaphase (where chromosomes line up along the metaphase plate), anaphase (where chromosome are pulled apart), and telophase/cytokinesis (where the nuclear envelope and nucleolus reappear and the cell divides). Meiosis occurs in sex/germ cells and turns a diploid (2n) parent cell into 4 haploid (n) daughter cells in a two-stage process, in which crossover between homologous chromosomes and the random allocation of maternal/paternal chromosomes to daughter cells work together to create genetic variability.

73
Q

What happens during prophase?

A

1st step of mitosis, nuclear membrane disappears, chromosomes condense, mitotice spindle forms. The DNA condenses such that distinct chromosomes become visible, as sister chromatids (or copies of a given chromosome) join at a region known as the centromere. The kinetochore assembles on the centromere, and is the site where microtubule fibers that extend from the centrosome and form the mitotic spindle attach to pull the sister chromatids apart in later stages of mitosis.

74
Q

What happens during metaphase

A

2nd stage of mitosis after prohphase, chromosomes line up along the metaphase plate

75
Q

What happens during anaphase?

A

3rd stage of mitosis after prophase and metaphase. Chromosomes are pulled apart

76
Q

What happens during telophase/cytokinesis?

A

4th stage of mitosis after prophase, metaphase, and anaphase. Nuclear envelope and nucleolus reappear and the cell divides.

77
Q

What happens during meiosis?

A

Meiosis occurs in sex/germ cells and turns a diploid (2n) parent cell into 4 haploid (n) daughter cells in a two-stage process, in which crossover between homologous chromosomes and the random allocation of maternal/paternal chromosomes to daughter cells work together to create genetic variability.

78
Q

Is DNA charged? Why or why not?

A

DNA is negatively charged due to its phosphate backbone.

79
Q

What are the subunits of DNA?

A

H1, H2A, H2B, H3, H4

80
Q

What makes up the histone?

A

The core a histone contains two dimers H2A and H2B and a tetramer of H3 and H4 while H1 serves as a linking unit. Approximately 200 base pairs of DNA can be wound around a histone, and the complex formed by DNA and a histone is known as a nucleosome.

81
Q

What are the two distinct forms of chromatin?

A

Euchromatin and heterochromatin

82
Q

Define euchromatin

A

Euchromatin is a loose configuration that is difficult to see under light microscopy and allows DNA to be readily transcribed. Throughout interphase (i.e., most of the cell cycle), DNA generally exists as euchromatin.

83
Q

Define heterochromatin

A

Heterochromatin is the tightly coiled, dense form of chromatin that is visible during cell division and is present to a lesser extent even during interphase.

84
Q

How does charge play a role in the interactions between histones and DNA?

A

Histones are highly alkaline and are positively charged at physiological pH, hich facilitates their interaction with the highly negatively charged phosphate groups on the backbone of DNA. Modifications like acetylation of histones reduce that positive charge, making histones interact with DNA less closely, which in turn facilitates transcriptional activity.

85
Q

Define spindle fibers. What are they made of?

A

Spindle fibers move chromosomes in mitosis and are made up of microtubules

86
Q

What is cytokinesis?

A

Cytokinesis is the splitting of the cell into two that occurs after both metaphase and anaphase

87
Q

What are the phases of mitosis?

A

prophase, metaphase, anaphase, and telophase

88
Q

How is meiosis different from mitosis?

A

Meiosis is essential for sexual reproduction. It takes place in germ cells (also known as sex cells). Meiosis differs from mitosis in that it has two stages and results in the formation of four daughter cells, each of which has only one copy of each chromosome (haploid, n), in contrast to mitosis, which generates cells with two copies of each chromosome (diploid, 2n) that are essentially identical to their parent cell.

89
Q

What happens in prophase I?

A

In prophase I of meiosis, homologous chromosomes (i.e., the maternal and paternal copies of a given chromosome) pair up with each other in a process known as synapsis, forming tetrads. While paired up, homologous chromosomes may exchange genetic information in a process known as crossing over. The crossing-over points are known as chiasmata. This process results in recombinant DNA that is another source of variation in sexual reproduction, in addition to the variability inherent to the process.

90
Q

What happens in metaphase I?

A

In metaphase I of meiosis, homologous pairs, which take the form of tetrads, line up at the metaphase plate. The orientation of the homologous pairs is random in terms of which side of the metaphase plate the maternal or paternal copy of a given chromosome in a homologous pair winds up.

91
Q

What happens in anaphase I

A

In anaphase I of meiosis, the homologous pairs are separated, and one member of each pair is pulled to each side of the cell.

92
Q

What happens in meiosis II

A

In meiosis II, which operates similarly to mitosis, the sister chromatids are split up into two haploid daughter cells.

93
Q

Define chemoreceptors

A

Chemoreceptors, including those of the taste buds in the tongue, olfactory receptors in the nose, carotid and aortic bodies, and chemoreceptor trigger zone of the medulla, are neurons involved in sensing molecules dissolved in gases or liquids.

94
Q

Define mechanoreceptors

A

Mechanoreceptors are neurons that respond to mechanical pressure or distortion. Cutaneous mechanoreceptors are responsible for somatosensation, while those embedded in muscles and ligaments are responsible for sensing muscular stretch and load, including in the afferent arm of a number of reflex arcs.

95
Q

Define osmoreceptors

A

Osmoreceptors (water homeostasis): respond to the osmolarity of blood

96
Q

Define photoreceptors

A

Photoreceptors (sight) respond to the visible spectrum of electromagnetic waves

97
Q

Define exteroreceptors and interoceptors

A

These receptors can also be broadly divided into exteroceptors, which respond to stimuli from the outside world, and interoceptors, which respond to stimuli generated within the body

98
Q

How are meiosis and mitosis similar?

A

During mitosis and meiosis II, sister chromatids are separated. mitosis separates sister chromatids to create two diploid daughter cells. Meiosis I separates homologous chromosomes to create haploid daughter cells, each of which divides again, separating sister chromatids in Meiosis II to create two haploid cells.

99
Q

Define parsimony

A

We want the phylogenetic tree that requires the fewest “events” (mutation, transfer, etc…) to produce the genetic picture.

100
Q

Define the Hardy-Weinberg equaiton

A

p+q=1 where p and q are the only two alleles in the population. Squaring the equation yields: (p + q)^2 = 12 → p^2 + 2pq + q^2 = 1. This second equation allows us to connect genotypes and phenotypes, because the p2 and q2 terms correspond to individuals homozygous for p and q, respectively, while the 2pq term gives the frequency of heterozygotes.

101
Q

What is the function of glycolipids? (cell)

A

Glycolipids act to provide energy and also serve as markers for cellular recognition.

102
Q

What is the funciton of phospholipids (cell)?

A

Phospholipids are a structural component of the membrane

103
Q

Which components of cells are physically connect by gap junction?

A

The cytoskeleton of one to the cytoskeleton of the other

104
Q

Chronic hyperglycemia leads ot the presence of what in the urine?

A

ketone bodies and glucose

105
Q

Meiosis I results in?

A

2 haploid cells with 23 chromosomes, each chromosome consisting of 2 sister chromatids.

106
Q

How is energy related ot equilibrium constant?

A

ΔG° = -RTlnK, For ΔG° to be negatvie ln(K) must be positive so K>1

107
Q

Define southern blotting

A

Southern blotting is a technique used to identify specific DNA sequences.

108
Q

Define western blotting

A

Western blots are used to identify protein

109
Q

Define northern blotting

A

Northern blots are used to identify RNA sequences

110
Q

Define Edman degradation

A

Edman degradation is a technique used to sequence proteins via successive cleaving of terminal amino acid residues

111
Q

Define nucleoside

A

A nucleoside is composed of a nitrogenous base and a five-carbon sugar (ribose or deoxyribose). Adenosine, is such a molecule. For adenosine, the nitrogenous base is adenine, while the five-carbon sugar is ribose (note the presence of both a 2’ and a 3’ hydroxyl group).

112
Q

Spontaneity is equivalent to what? (in terms of energy and equilibrium)

A

∆G < 0, Keq > 1, and E° > 0

MCAT (6 decks)

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