NS4: BBCF

Question 1

what happens if you inhibit cytochrome c oxidase?

Answer 1

Cytochrome c oxidase is an enzyme responsible for electron transfer in the electron transport chain (ETC), so inhibiting it would slow or stop the ETC. As a result, ATP production would be dramatically reduced.

Question 2

carbonic anhydrase

Answer 2

enzyme that assists rapid inter-conversion of carbon dioxide and water into carbonic acid, protons and bicarbonate ions

can work in both directions

• • forward decreases pH
• • backwards increases pH

Question 3

integrins vs cadherins

Answer 3

Integrins are transmembrane receptors that modulate cell-to-extracellular matrix interactions. Specifically, these proteins often attach the cell to collagen and fibronectin fibers.

Vs. Cadherins are transmembrane proteins which play a primary role in cell-to-cell adhesion (remember that C stands for cell-to-cell), forming adherens junctions to bind cells within tissues together.

Question 4

how does dna replicate

Answer 4

Dna replicates in a semiconservative manner, meaning that each replicating strand of double-stranded DNA (dsDNA) produces two daughter molecules, each of which contains one parental and one new strand.

Question 5

calcium functions

• osteoblasts
• osteoclasts

Answer 5

Calcium plays a key role in multiple physiological functions, most notably in bones, neurotransmitter release, muscle contractions, and as a second messenger within the cell.
– levels are regulated by parathyroid hormone and calcitonin to facilitate bone remodeling, or the degradation of older, existing bone and the formation of new bone in its place

osteoblasts are cells that help build bone, and therefore reduce blood calcium levels by “storing” calcium in bone tissue

osteoclasts are cells that break down bone, releasing calcium into the bloodstream

Question 6

calcitonin

Answer 6

released by C cells of the thyroid and decreases plasma concentrations of Ca2+ stimulates bone formation by increasing osteoblast activity and decreasing osteoclast activity

Question 7

parathyroid hormone

Answer 7

secreted from the parathyroid in response to low blood calcium levels and elevates blood calcium levels by decreasing bone formation by osteoblasts and increasing bone degradation by osteoclasts

Question 8

vitamin D

Answer 8

inactive form = CHOLECALCIFEROL, which will turn into the active form CALCITRIOL

Calcitriol has a similar function to PTH in that it increases serum calcium levels, but it does so primarily through a different mechanism: it promotes the absorption of Ca2+ from the gastrointestinal tract.

Question 9

antibiotics

antibiotic resistance

Answer 9

Antibiotics: compounds designed to kill prokaryotes, generally work by targeting structures specific to prokaryotes, thus not harming eukaryotic host cells

Antibiotic resistance: caused by genes found on plasmids (non-chromosomal bits of circular prokaryotic DNA) and spread through conjugation

Question 10

types of symbiosis

Answer 10

occurs when two distinct organisms live in close proximity with each other, affecting each other’s life cycle

Parasitism benefits one species at the cost of harm to another.

Competition is when two species compete for access to a limited resource.

Mutualism requires that both species benefit.

Commensalism is when one species benefits but the other species is neither helped nor harmed

Question 11

sarcomere

Answer 11

fundamental unit of contraction; consists of a band of thick myosin fibers and half of each of the two adjacent bands of thin fibers

divided into I-band, A-band, H-zone, Z-line, and M-line

The M-line defines the middle of the sarcomere, running through the middle of the thick filaments, while the Z-lines define the edges, running through the middle of the thin filaments.

The I-band refers to the region where only thin actin filaments are present, and the A-band is everything else, that is, the entire region where thick filaments are present, including areas of overlap with the thin filaments.

The H-zone refers to the region where only thick filaments are present, making it analogous to the I-band.

During contraction, the M-lines and Z-lines come closer together, the A-band stays the same, and the I-band and H-zone become shorter.

Question 12

what is the signal for contraction

Answer 12

The signaling for contraction occurs when the neurotransmitter acetylcholine is released into the neuromuscular junction.

Acetylcholine binds to receptors on the cell membrane, which is known as the sarcolemma in muscle cells

Sarcolemma then depolarizes in response. This results in an action potential, and when the action potential reaches the sarcoplasmic reticulum, Ca2+ is released into the sarcoplasm (recall that this is just muscle-speak for the cytoplasm).

Once in the sarcoplasm, Ca2+ can bind to troponin, which allows contraction to take place

Question 13

what is the basic mechanism of contraction; aka sliding filament model

Answer 13

Striated muscle fibers contain long rod-like myofibrils that are composed of alternating units of thick (myosin) and thin (actin) fibers that overlap with each other.
– contraction allows for the interwoven myosin and actin fibers to slip past each other

During contraction, the actin and myosin filaments slide past each other through what is known as a cross-bridge cycle, in which a cross-bridge is formed between myosin and actin, and a power stroke provides the force of contraction. Immediately after a power stroke, myosin and actin are bound together, and the cycle begins again.

Question 14

what is the specific binding pathway of skeletal muscle contraction

Answer 14

ATP binds to the myosin head, causing a conformational change that releases it from actin.

Then, a protein called tropomyosin moves back into place to block strong interactions between actin and myosin.

The ATP molecule is then hydrolyzed. This is a strongly exergonic reaction and is used to move the myosin head into the “cocked position,” where it can interact weakly with actin.

Tropomyosin is ultimately removed by Ca2+ through a somewhat complex mechanism. At this point, the myosin head can bind tightly to actin.

The power stroke then occurs via a conformational change that happens when Pi is released, resulting in a force of about 2 pN.

ADP is then released and actin and myosin are essentially stuck together until another ATP binds to myosin so that the process can start again.

Question 15

mnemonic “More blasting gas, I’m nervous”

Answer 15

outlines the process of morula to blastula to gastrula to neurulation

morula: solid ball of cells that arises after zygote undergoes a series of cleavages
blastula: hollow ball of cells; has two poles (animal and vegetal)
gastrula: cell migration to the interior of the blastula via the blastopore, resulting in the formation of the germ layers

Question 16

define the following:

• blastocyst
• inner cell mass
• trophoblast
• blastocoel

Answer 16

The blastocyst consists of an inner cell mass (ICM), along with an outer cell layer called the trophoblast, which surrounds both the ICM and blastocoel (fluid filled cavity)

The inner cell mass is the mass of cells within the blastocyst that will eventually give rise to the fetus.

Question 17

Isoelectric focusing

Answer 17

requires the use of a gel that has a stable pH gradient in order to separate proteins by isoelectric point, which depends on the amino acid composition of the protein

The protein will cease to migrate when it reaches the region of the gel where the pH of the gel equals the pI of the protein. At this point, the protein will stop migrating because the net charge of the protein will be 0, so it will not experience any electric force.

Question 18

anode v cathode charges

• ief
• galvanic
• electrolytic

Answer 18

In an IEF setup, the cathode is the negatively-charged electrode.

Vs. In a galvanic (voltaic) cell, the anode is considered negative and the cathode is considered positive.

Vs. in an electrolytic cell, the anode is taken to be positive while the cathode is now negative.

Question 19

stereospecific enzymes

Answer 19

Many of the enzymes used in the body are stereospecific – they will only react with one particular stereoisomer form of a molecule and will only catalyze a reaction that produces a particular isomer of the product. Often drugs are administered as a racemic mixture because the workup in the lab produces such a mixture even though only one of the isomers has any biological effect.

Question 20

autonomic nervous system

Answer 20

controls involuntary responses in the body

Sympathetic nervous system: fight or flight response

Parasympathetic: rest and digest response

Question 21

substitutions

Answer 21

aka point mutations; genetic mutations of a single nucleotide

Silent: mutated codon codes for the same AA as the original

Missense: mutated codons codes for a different AA than the original

Conservative: missense AA encoded but has similar functional properties as the original, thus has a smaller effect on functionality of the protein coded for by the gene

Non-conservative: missense AA encoded with dissimilar functional properties as the original, thus leading to malfunctioning or nonsense mutations

Question 22

Frameshift mutation

Answer 22

caused by insertion of deletion of nucleotides

Deletion: literal deletion of part of a sequence

Insertion: insertion of a sequence

Question 23

UTR

Answer 23

untranslated region

region of mRNA that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript, thus must be transcribed but not necessarily (fully) translated

Question 24

In the first trial of the PCR procedure, only one primer was added to the mixture. What was the most likely outcome during this trial?

Answer 24

When performing PCR, if only one primer is added to the mixture, then that primer will bind to one of the strands and initiate replication of that strand to produce the complementary strand. For one double-stranded template DNA molecule, after one cycle, we are left with two of the complementary strand while still having only one of the strands where the primer binds. In the next cycle, the primer again binds to the strand to which it is complementary. Therefore, only the complementary strand will be replicated again; this time we have three of the complementary strand.

Question 25

mature mrna

DNA coiling in order of compactness

Answer 25

A mature mRNA consists of a 5’-cap (one base pair), the 5’ UTR, coding regions, the 3’ UTR, and a poly(A) tail.

In increasing order of compactness: DNA helix > euchromatin > heterochromatin > nucleosome

Question 26

intermediate filaments vs microtubules

Answer 26

Intermediate filaments such as keratin are directly responsible for structural integrity in skin.

Microtubules are not involved in structural integrity, but in mitosis, meiosis, cell trafficking of vessels, and ciliar/flagellar motion. Microtubules are composed of tubulin protein dimers.

Question 27

reflex arc

Answer 27

Voluntary muscles may contract involuntarily due to a reflex arc. The classic example is the patellar tendon reflex, in which sudden stretching of the patellar tendon leads to an involuntary contraction of the quadriceps. Such contraction occurs before the signal has even reached the brain.

This arc contains a sensory neuron, which carries sensory information from peripheral receptors toward the spinal cord, and a motor neuron, which carries a signal from the spinal cord to an effector muscle. This particular reflex arc also contains an interneuron, which is a neuron within the spinal cord that synapses on both the sensory and motor neurons, connecting them.