Practice exam #1 test corrections

only content issue material

In terms of expressed genes in somatic cell and germline cells, which of the two cannot pass their genes/mutations to offspring

somatic cells

Exons vs introns

exons are spliced(not removed) and introns are removed from mRNA. Exons will code for proteins while introns will not. You will see exons in DNA, pre-mRNA, and mature mRNA, you will not see introns as they are removed. Exons contain the info that is translated into a protein—they’re EXpressed. Introns stay IN the nucleus before being removed from the coding sequence by RNA splicing.

Splice acceptor sites

they help spliceosomes know where to cut. theyre located at the end of an intron. When this site is recognized, the exons are spliced and introns are removed. If mutation occurs to this site, exons may not be recognized

mature mRNA

mature mRNA that is secreted or that will locate to the cell membrane will contain the signal sequence. It will not contain introns because they are removed, nor is a promoter

nuclear localization signal

a sequence that tags for it to be transported into the nucleus

Steroid

composed of a 6-6-6-5 fused ring assembly, which is a total of 4 fused rings

Neuron firing threshold

this threshold makes it more challenging for a neuron to fire an action potential. It is like a cap that tells the neuron to stop firing because the threshold has been reached.

Na+ K+ ATPase

This deals with ATP hydrolysis which involves ion concentrations and enzymes to produce ADP+Pi. This relates to enzyme activity, reaction rate/activity, it does not involve free energy because that discusses whether the transport is energetically favorable

What is the function of the Na⁺K⁺ ATPase during a neuronal action potential?

The restoration and maintenance of the resting potential relies on Na⁺/K⁺ ATPase. This is achieved by moving three Na⁺ out of the cell for every two K⁺ ions that are brought into the cell.

In which direction does the Na⁺K⁺ ATPase transport ions across the cell membrane upon ATP hydrolysis?

Upon ATP hydrolysis, three Na⁺ are transported outside the cell and two K⁺ are transported inside the cell against their concentration gradient.

what is p65 and cRel?

They are transcription factors. By definition, transcription factors regulate the expression of other genes by binding to the promoter or the enhancer of the gene located on the DNA

Identifying chemical compound structures to decide how it enters a cell

Charged molecules cannot diffuse through a membrane(Na+, K+, Ca2+, Cl-, HCO3-). They enter via ion channels, ion pumps, and transport proteins(charged=protein transport)

Polarity: If not charged, check for polarity. Polar molecules will have lots of O, N, OH groups, NH2 groups, and carbonyls. They dissolve well in water, but cannot cross hydrophobic membrane. So they require carrier proteins, facilitated diffusions, and active transport. Nonpolar compounds(like aromatic) will have a lot of C and H w/ few to no O or N. These only need simple diffusion.

Size: Small molecules are most likely nonpolar and will need simple diffusion. For larger molecules(DNA, proteins, polysaccharides), these need endocytosis, vesicles, receptor mediated endocytosis

protein kinases

they activate proteins via phosphorylation

proteolytic cleavage

when a protease cuts a larger protein into a smaller, active form

GTP binding

when a protein binds GTP to turn itself on

membrane association

a protein binds to or inserts into a membrane to function

Transcription factors

are proteins that turn genes off and on and decide which genes get made into mRNA. for these genes to be affected by specific transcription factors, they need to have the specific binding sites for them

what does ATPase activity(ATP hydrolysis) produce

ADP and inorganic phosphate(Pi)

Cholesterol-rich domains

small regions of the cell membrane that contain a high concentration of cholesterol and certain lipids- often called lipid rafts

The initial filtration step in the glomerulus of the mammalian kidney occurs primarily by:

glomerular capillary pressure, capsular hydrostatic pressure, and blood colloid osmotic pressure; The glomerular capillary pressure will force filtrate from a capillary into Bowman's capsule; the other two forces promote movement of the filtrate in the opposite direction. This process is not a countercurrent exchange system, and water and electrolytes are not actively transported from the glomerulus into bowman’s capsule. It is not a countercurrent exchange system, water is not actively transported from the glomerulus into bowman’s capsule, electrolytes are not actively transported from the glomerulus into bowman’s capsule

Half life: If given the time it takes for urea to fall by 1/2= 0.5 hours, How long would it take for urea to be eliminated from the body given it takes 5 half lives

0.5 × 5= 2.5

Enzymes do their job by altering what

co-localizing substrates, altering pH of environment, and altering substrate’s shape. Altering the shape does not mean it alters its primary structure, that would mean it affects its amino acids

What is an enzyme

a biological catalyst that lowers activation energy, very specific, and cannot be used up. Usually ends in -ase

Enzymes: enzyme assay

used for measuring enzyme activity, it measures for its specific enzyme bc enzymes have specificity. Example: Ornithine decarboxylase assay is said to be highly specific, meaning it will measure ornithine decarboxylase activity only

What is needed to make more copies of a gene

mRNA; DNA, tRNA, and rRNA are not directly changed or correlated to making more of a protein via transcription.

Cell cycle: in which cycle does no cell division occur

INTERPHASE; The order goes interphase→PMAT and if cells are growth arrested, this infers no cell division. There is cell division however in PMAT steps

Do erythrocytes contain DNA?

NO, and because they do not have DNA they cannot affect other cells via DNA

Reasoning about research design and execution: why would a researcher want to growth arrest cells in a mixture of different cells when performing a cell count?

It ensures that the only cells the researcher wants to divide are counted. Example: endothelial cells and supportive cells are mixed together and a cell count is performed electronically. Pericytes are growth arrested so to allow proper cell count

How are two nucleotides linked together

by a phosphodiester bond between the sugar base of one nucleotide(thymine) and the phosphate group of the adjacent nucleotide(adenine) in a way that the 5’ end bears a phosphate and the 3’ end a hydroxyl group

How does Addison’s disease affect the secretion of the hypothalamic factor(CRH)

A person with Addison’s disease cannot secrete glucocorticoids or mineralocorticoids, cortisol or aldosterone. The hypothalamic factor stimulates the release of ACTH from pit. gland. ACTH triggers cortisol release, as cortisol levels increase, it will inhibit the hypothalamic factor(CRH), which stops the cycle. A person with addisons disease does not adequately

What is gluconeogenesis and what role does cortisol play in it

the process that forms glucose(a carbohydrate) when it is LOW. It does this by converting noncarbohydrates such as amino acids and lipids into glucose. Cortisol stimulates gluconeogenesis, so inhibiting cortisol will downregulate gluconeogenesis

glycolytic pathway: What role does insulin play in this pathway?

refers to glycolysis, the process of breaking down glucose IN CELLS. When insulin stimulates glycolysis(breaking down of glucose in cells) this results in a decrease of cellular concentration of glucose in the cell. Because there is less glucose INSIDE the cell, glucose uptake will increase to compensate for that change, therefore bringing in more glucose.

Which organelle would you see polypeptides being cleaved into mature form and secreted from the cell

Endomembrane system; this is referring to the ER and golgi apparatus in cells. They modify proteins(polypeptides) that will be secreted. Example: insulin cleavage is most likely to occur in the endomembrane system, not the nucleus, ribosomes, or cytoplasm.

Despite the effects of diabetes, the brains of diabetic patients still receive adequate nourishment. This is most likely because the brain uses:

insulin-independent transporters for the uptake of glucose; glucose is the main fuel for the brain, not fatty acids. The brain contains glucose transporters that are insulin independent. Meaning that the transporters do not need insulin in order to bind and transport glucose.