B MCAT - Bio, Biochem II Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Osmosis

A

Osmosis is the movement of water across permeable membranes from areas of lower solute concentration to areas of higher solute concentration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Osmolarity
When separated by a semipermeable membrane, how will water move?

A

Osmolarity describes concentration of solute/solution. Low osmolarity = small amount of solute compared to solution. High osmolarity = large amount of solute compared to solution. When separated by a semipermeable membrane, water will move from areas of lower solute concentration to areas of higher solute concentration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Otolithic organs

A

The otolithic organs are the saccule and utricle in the inner ear, related to vestibular sense. There are CA crystals adjacent to hair cells in a gel that are sensitive to gravity–they move with gravity when you stand up vs. lay down.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

endolymph fluid

A

fluid that fills the semicircular canals in inner ear to facilitate vestibular sense.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

mechanoreceptors

A

mechanoreceptors sense PRESSURE.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

tonicity

A

the ability of an extra-cellular solution to move water in or out of the cell.

If a cell is placed in a hypertonic solution, there will be a net flow of water out of the cell, and the cell will lose volume. A solution will be hypertonic to a cell if its solute concentration is higher than that inside the cell, and the solutes cannot cross the membrane.

If a cell is placed in a hypotonic solution, there will be a net flow of water into the cell, and the cell will gain volume. If the solute concentration outside the cell is lower than inside the cell, and the solutes cannot cross the membrane, then that solution is hypotonic to the cell.

If a cell is placed in an isotonic solution, there will be no net flow of water into or out of the cell, and the cell’s volume will remain stable. If the solute concentration outside the cell is the same as inside the cell, and the solutes cannot cross the membrane, then that solution is isotonic to the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

hydrostatic pressure

A

Hydrostatic pressure is the pressure a liquid exerts on its container, and reflects the volume of liquid in a space.

P=density x g x h

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

congenital disorder

A

present since birth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

receptor tyrosine kinases

A

Receptor tyrosine kinases are integral membrane proteins that relay a “message” from the extracellular side of the cell to the intracellular side of the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

hydrostatic vs. oncotic pressure in the capillaries

A

Hydrostatic pressure is the force that pushes blood out of the capillaries.

Oncotic pressure is the force that pushes blood into the capillaries.

Together, they determine fluid flow from the capillaries to surrounding tissue.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

heterocycllic

A

a compound whose molecule contains a ring of atoms of at least two elements (one of which is generally carbon).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

alveoli

A

tiny air sacs of the lungs which allow for rapid gaseous exchange.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

genetic recombination

A

Genetic recombination leads to the creation of an organism with DNA that differs from its parent organism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

viral replication–lytic vs. lysogenic

A

lytic virus replication = immediately take over host’s machinery, replicates itself, lyse (destroy) host, and spread to new hosts. “impatient”

lysogenic = (prophage) repressed/latent to start, host doesn’t know it is there until activated, then replicated with host DNA. “hitch a ride”
With a lysogenic virus, the new daughter cells are infected with the virus, eventually leading to a neoplasm, also known as tumor.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

retrovirus

A

(not quite lytic or lysogenic)

MAKES DNA FROM RNA.

Infect animals, not bacteria.

A retrovirus is an enveloped virus with 3 unique proteins.
Enters host through endocytosis or similar mechanism.
Replicates its RNA strand to DNA.
Then replicates again to double stranded DNA with “sticky” ends.
Then travels to host DNA and integrates. Host can’t tell it is foreign and it is transcribed like normal DNA.
Self assembly of new viruses–they bud off from cell membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Prion

A

A prion is similar to a virus but does NOT contain genetic material.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Two ways to cleave peptide bonds

A

1) Acid hydrolysis–add water and heat and peptide bonds will cleave. Non-specific.

2) Proteolysis–Use protease enzymes to target specific bonds in the polypeptide chain.
Ex. protease enzyme trypsin. Only cleaves on the carboxyl side (C-terminal) of basic amino acids like arginine and lysine. (trypsin also used by our pancreas to digest food).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Catalytic functions of enzymes

A

Enzymes can be proton carriers; speed up transfer of H to help lower Ea for rxn.
E+S>ES>E+P

Covalent catalysis–enzymes can carry electrons (be an “electron sink”) as they move around, for example in decarboxylation.

Electrostatic catalysis–enzymes can stabilize charge. For example, DNA is a very negatively-charged polymer because of all the phosphate groups. DNA polymerase includes metal Mg^2+ to stabilize the DNA’s neg charge.

Proximity and orientation effects–enzymes can help make sure that molecules are positioned to collide and react. Increase frequency of collisions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Cofactors and coenzymes

A

Help an enzyme along by carrying electrons or participating in a reaction.

Many coenzymes and cofactors come from our diet in form of vitamins and minerals.

Vitamins are organic cofactors and coenzymes. B3, or niacin, is a precursor to NAD and B12 is a precursor to CoA.

Minerals are inorganic (no C) cofactors. Mg^2+ is used by DNA polymerase. Ca can BOTH act as a cofactor, and is a critical molecule itself as well.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Induced fit model of enzyme binding
(vs. active site model)

A

A substrate for an enzyme is the reactant of the reaction that the enzyme catalyzes.

An enzyme and a substrate must come into close physical proximity for binding to occur, and such proximity can introduce physical forces that alter the shape of the enzyme.

The induced fit model of enzyme binding states that the substrate itself alters the enzyme active site.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Km

A

Km is the substrate concentration [s] where the enzyme rate V is at 1/2 of the maximum possible rate Vmax.
moles per liter (M)

Lower Km = more efficient enzyme.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Kcat

A

The turnover number; how many reactions an enzyme can turn over in a second. sec^-1

Higher Kcat = more efficient enzyme.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

catalytic efficiency of an enzyme =

A

catalytic efficiency of an enzyme = Kcat/Km

Higher Kcat = more efficient
Lower Km = more efficient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

homotropic vs. heterotropic in enzyme feedback loops

A

In enzyme feedback loops, a homotropic regulator acts as both the substrate and the regulator (eg. Abundance of ATP in cell says, “we have ATP” and inhibits glycolysis) .

A heterotropic regulator acts only as the regulator, and is not the substrate (eg. Abundance of AMP says, “we need ATP” and activates glycolysis).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Ligand

A

The ligand is a chemical messenger released by one cell to signal either itself or a different cell. The binding results in a cellular effect, which manifests as any number of changes in that cell, including altering gene transcription or translation or changing cell morphology.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Protein functions

A

Enzymes can be proteins (though not all enzymes are proteins).

Proteins also function as:

Receptors/ion channel proteins. Eg. insulin is a ligand that binds to a protein receptor on the cell membrane when glucose is abundant to trigger the absorption of glucose.

Transport proteins–Bind small molecules and transport them. Must have high affinity for their ligand when the ligand is in high concentration, and low affinity when the ligand is in low concentration. Eg. hemoglobin.

Motor proteins–myosin (generating contracted muscles), kinesin (intracellular transport), and dynien (intracellular transport and motility of cilia).

Antibodies–protein components of the adaptive immune system. The antigen is the antibody’s ligand.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Enzyme categories

A

Some enzymes are proteins (made up of primary, secondary, tertiary, and quaternary structures).

Enzymes can also be small inorganic molecules (eg. Mg^2+

Enzymes can be small organic substances that act as coenzymes (eg. flavin).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Covalent modifications to enzymes

A

Covalent modifications to enzymes are mostly to protein enzymes after synthesis of an AA polymer = post-translational modifications. Usually adding or removing small functional groups.

methylation (adding CH3)
acetylation (adding keytone + CH3)
glycosylation (adding a sugar)

We often think of competitive, noncompetitive, and uncompetitive enzyme inhibition. There is also “suicide inhibitors” in enzymes, which is a type of covalent modification. Permanently bind target, so after they bind, there are done.

29
Q

zymogen

A

Zymogens are inactive enzymes that require covalent modifications in order to become active.

eg. The pancreas releases TRYPSINOGEN (-ogen indicates it is a zymogen) into the intestine, where it is covalently modified by enterokinase into it’s active form TRYPSIN. This system keeps trypsin from breaking down proteins in the intestine that we need.

30
Q

properties of allosteric enzymes

A

Reversible, noncovalent binding of regulatory compounds

31
Q

Ribosome sedimentation coefficients of eukaryotes vs. prokaryotes

A

For translating mRNA into proteins, eukaryotes have an 80S ribosomes (made of a 40S+60S subunit), faster than prokaryote’s 70S ribosomes (a 30S+50S subunit).

Because bacteria’s ribosomes are different from those of eukaryotes, many antibiotics target the 30S or 50S subunit of a bacteria to stop translation.

Related, bacterial ribosomes start translation with a methylated methionine, which alerts eukaryotes to the presence of bacteria.

32
Q

Deacetylation of histones has which of the following effects?

A

Coiling of the histone structure, preventing it from being accessed by transcriptional machinery

33
Q

Methylation of CpG islands is essential to which process(es)?

A

Stable silencing of DNA as cells terminally differentiate

34
Q

What is the function of the spliceosome?

A

To cleave introns from RNA and ligate the cut ends.

35
Q

A non-conservative genetic mutation is one in which:

A

The new amino acid has different biochemical properties than the original.

36
Q

endogenous vs. exogenous mutagen or carcinogen

A

Endogenous means it is made in the body. Exogenous means it came from outside the body.

Not all mutagens are carcinogens.

37
Q

Synaptonemal Complex

A

During the first stages of meiosis, the chromosome axes are organized along a protein scaffold in preparation for recombination and their subsequent segregation. This scaffold, known as the synaptonemal complex (SC), is critical for the regular progression of recombination. A complex relationship exists between the organization of the SC, the frequency of recombination, and the likelihood of improper chromosome segregation.

The SC provides structural support for recombination (crossover), is made of proteins, and is formed between the sister chromatids.

38
Q

Hardy Weinberg equilibrium

A

For a population to be in Hardy-Weinberg equilibrium, mating must be random, and natural selection must not be occurring (in the context of a particular trait).

39
Q

Restriction Enzymes

A

Restriction enzymes destroy unprotected DNA, which is usually foreign. Hosts can protect their DNA by methylation.

In nature, restriction enzymes are found in bacteria as a defense against invading viruses.

40
Q

The bottleneck effect in nature

A

Sometimes when a population becomes very small (eg. flies dying in a drought), one trait can randomly be present in larger proportions than another trait in the remaining individuals.

(note the difference between this vs. adaptation or natural selection, which do NOT occur randomly and take generations).

41
Q

inbreeding

A

when a population has much shared ansestery.

42
Q

stabilizing selection

A

Stabilizing selection describes a process in which extremes of a trait (being very tall or very short for example) are selected against and an intermediary trait (like being average height) is selected for.

43
Q

High fecundity

A

A high fecundity means an organism is able to produce more offspring.

44
Q

pre-zygotic reproductive isolation

A

Pre-zygotic reproductive isolation refers to barriers that prevent two organisms from mating and occur before a zygote is successfully formed by the combination of a sperm and an egg.

45
Q

Temporal isolation

A

Temporal isolation is when organisms are separated by a factor of time, such as day and night or summer and winter, and therefore cannot reproduce.

46
Q

Disruptive selection

A

Disruptive selection occurs when two extreme phenotypes on a continuum are selected for.

47
Q

Coevolution

A

Coevolution occurs when two species evolve alongside each other and exert evolutionary pressures on one another.

48
Q

Differential reproduction

A

Differential reproduction is the idea that certain individuals are more likely to reproduce than others, and will therefore have their genetic traits expressed at a higher rate in future generations.

49
Q

Group selection

A

Group selection is the idea that traits that benefit the population as a whole will still be selected for even if they don’t directly help the individual expressing that trait to survive and reproduce.

Eg. One monkey putting himself in danger to alert other monkeys of an incoming predator.

50
Q

Genetic drift

A

Genetic drift refers to changes in the frequency of alleles in a gene pool, simply due to chance.

51
Q

Adaptive radiation

A

Adaptive radiation is when one lineage diverges into many others as isolated populations occupy different niches.

eg. As prehistoric humans moved to different regions of the globe, different populations began expressing different concentrations of melanin in their skin.

52
Q

describe enthalpy (delta H) in the context of sweating

A

H2O(l) > H2O(g)
delta H = H of H2O(g) minus H of H20(l)= positive value

When you sweat, your body releases energy as heat. It takes heat for H2O to turn from liquid to gas, so the delta H of the rxn is positive. The surroundings absorb the heat, and you cool off.

Enthalpy H units of Joules/mol

53
Q

Heat vs. temperature

A

Heat (q) is always in the context of heat transfer between a system and its surroundings.

Temperature is an absolute measure of average kinetic energy of a system.

54
Q

ATP/ADP e

A

Exergonic ATP hydrolysis releases energy to drive endergonic processes. ATP + H2O > ADP + 1Pi

ADP phosphorylation is an endergonic process.

55
Q

ATP > ADP rxn, endergonic/exergonic?

A

The exergonic ATP hydrolysis rxn releases free energy to drive endergonic processes. ATP + H2O > ADP + 1Pi

ADP phosphorylation is an endergonic process.

56
Q

glucose + O2 >

A

glucose + O2 > H2O + CO2

In aerobic respiration, electrons are ultimately transferred from glucose to oxygen (the final e- receptor).

57
Q

How does an antibiotic work?

A

An antibiotic increases the activation energy (Ea) of a certain bacteria’s chemical reactions by that depend on the enzyme that the antibiotic is bound to. The antibiotic distorts the binding site, inhibiting the bacterial enzyme.

If this fails, the bacteria can build resistance to the antibiotic.

58
Q

The electron transport chain is an important chemical reaction of cellular respiration. What would occur if oxygen was not present in the electron transport chain (anaerobic conditions)?

A

Release of free energy is typical of exergonic reactions.

Electron transport chain is characterized by decreasing free energy levels on each step.

Oxygen is the final electron acceptor in electron transport chain. Its absence would reduce the overall free energy released, thus this exergonic reaction would have a smaller magnitude ΔG in the absence of oxygen.

59
Q

Why does muscle contraction result in higher body temperature?

A

Muscle contraction depends on energy released from ATP hydrolysis, which has a negative delta G.

60
Q

free energy equation

A

deltaG=deltaH - (T)(deltaS)

61
Q

What is a good prediction for teh reduction potential for the half rxn of the reduction of NAD+?

A

Reduction potential will be less than zero.
The reducer is stronger when it has a more negative reduction potential.

NAD+ + H+ + 2e- > NADH

62
Q

carbohydrates

A

carbon + water

1 C + 1 H2O = monosaccharide (sugar)

Always a 1:2:1 ratio of carbon:hydrogen:oxygen.

Examples: glucose (energy), cellulose (cell walls), ribose (DNA)

glucose is a “hexose” with 6 carbons.

63
Q

Defining characteristic of a transcription factor

A

The defining characteristic of a transcription factor is that it has a DNA-binding domain that allows it to bind to regulatory nucleic acid sequences in a gene to alter transcription.

64
Q

Microglia cells

A

Microglia are phagocytotic innate immune cells specific to the brain. The other cells are adaptive immune system cells and require activation by microglia in order to mount an immune response.

65
Q

types of intercellular connections

A

Desmosomes are intercellular junctions that function as anchors to form strong sheets of cells.

Gap junctions are intercellular junctions that provide cytoplasmic channels between adjacent cells.

Intercalated discs are specialized intercellular junctions between cardiac muscle cells that provide direct electrical coupling among cells.

Tight junctions are intercellular junctions that prevent the movement of solutes within the space between adjacent cells. In blood capillaries, neighboring endothelial cells form tight junctions with one another to restrict the diffusion of harmful substances and large molecules into the interstitial fluid surrounding the brain (blood brain barrier).

66
Q

gallbladder

A

in stomach, stores bile and helps break down fatty foods

67
Q

neoplasm

A

an uncontrolled growth of cells.

68
Q

Which embryological stage divides the embryo in two halves establishing bilateral symmetry in mammals?

A

The formation of the neural tube during neurulation divides the embryo in two symmetric halves.