MCAT Bio/Biochem Flashcards
How does cholesterol affect membrane fluidity at both high and low temperatures?
High Temp: Cholesterol stabilizes phospholipids and decreases fluidity
What are the key differences between Meiosis and Mitosis?
Both Meiosis and Mitosis consist of the separation of sister chromatids
Which viruses require RNA replicase? How about RNA transcriptase?
RNA replicase is only needed for negative-sense single-stranded RNA viruses –> Creates positive-sense RNA strands to be translated using host cell machinery
What are the 3-letter and 1-letter abbreviations for every amino acid?
Every 3-letter and single letter abbreviation of amino acids
Where does the active replication or synthesis of viral proteins occur in host cells?
Viral proteins are synthesized using host ribosomes, which are located in the rough ER
What are viral envelopes primarily made up of? Where are viral genetic material and associated enzymes located?
Viral envelopes are primarily made up of phospholipids (cell membrane) and glycoproteins (recognition and interaction with cell receptors); Viral genetic material and associated enzymes are contained in the virion, not the envelope
Describe the investment phase of glycolysis
By the end of the investment phase of glycolysis (first 5 steps), 1 molecule of gluose is converted to –> 2 G3P + Net loss of 2 ATP
What is difference between facultative and obligate aerobes/anaerobes?
Facultative Aerobes can use oxygen as an electron acceptor in presence of oxygen, but it can also survive in an anaerobic environment by deriving energy solely from glycolysis and subsequent fermentation
Which enzymes are used ONLY in gluconeogenesis and not glycolysis?
Enzymes only used in Gluconeogenesis include: Pyruvate carboxylase, Fructose 1,6-bisphosphatase, Glucose 6-phosphatase
What is the rate-limiting step of Glycolysis? Which enzyme is involved in this step?
Rate-limiting step of Glycolysis is the phosphorylation of F6-P into F1,6-BP by the enzyme Phosphofructosekinase-1; Uses 1 ATP
How are Glucokinase and Hexokinase regulated, respectively?
Hexokinase is inhibited by high levels of G6-P, Glucokinase inhibited by low blood sugar
What are the functions of DNA Polymerase A and DNA Polymerase D?
DNA Polymerase A initiates synthesis in eukaryotes; DNA Polymerase D synthesizes new nucleotides to each preceding 3’ OH group (Requiers RNA primer);
What is the function of Histone Deacetylase?
Histone Deacetylase removes negatively charged acetyl groups, causing them to be more positively charged and interact more closely with DNA surrounding them –> Reduces transcription of genes on DNA
What is 3’-5’ exonuclease activity? Which enzymes posses this activity?
DNA Polymerase can perform a proofreading mechanism termed 3’-5’ exonuclease activity, where DNA Polymerase excises mismatched bases and replaces them with the correct base at that position
What is the overall rate of a reaction consisting of three individual reaction rates: K1, K2, and K3?
Overall Rate of Reaction = K1 x K2 x K3…etc
What is alternative splicing? What is its benefit?
Alternative Splicing is a mechanism through which some exons can be spliced out, allowing for # of proteins to be 10x that of # of genes
What are the definitions of Penetrance and Expressivity, respectively?
Penetrance = How often a mutation is phenotypically expressed (Mutated genotype should display disease phenotype), Expressivity = Intensity or extent of variation in a phenotype
What is the relationship between genetic linkage and physical location of genes on a chromosome?
Genes that are further apart are less likely to be linked
What are the equations for allele frequency in a population under Hardy-Weinberg equilibrium?
Allele Frequency Equations: 1) p + q = 1 2) p^2 + 2pq + q^2 = 1
What is a key intermediate in the Kreb’s Cycle that is used in the export of gluconeogenic substrates from the mitochondria?
Malate is a key intermediate in the Kreb’s Cycle that is used in the export of gluconeogenic substrates from the mitochondria
What is the function of Complex I in the ETC?
Complex I receives electrons from NADH and results in translocation of 4 protons across inner mitochondrial matrix
What is the irreversible, rate-limiting step of the Kreb’s Cycle?
The decarboxylation of isocitrate to form A-ketoglutarate (5 C’s) is the irreversible, rate-limiting step of the Kreb’s Cycle
What is epidemiology?
Epidemiology is the study and analysis of the distribution, patterns and determinants of health and disease conditions in defined populations
Which nucleotides are Purines? Which are Pyrimidines?
Purines: A and G (Pure as Gold) Pyrimidines: C, U and T (CUT the Py)
What are the first two steps of Glycolysis? What enzymes catalyze these reactions?
Step 1: Glucose –> G6P (Catalyzed by Hexokinase) Step 2: G6P –> F6P (Catalyzed by G6P isomerase)
What is Substrate-Level Phosphorylation? When does it occur during Glycolysis?
*Substrate-Level Phosphorylation: Process by which a phosphate group is transferred to ADP/GDP to produce ATP/GTP *Occurs during anaerobic Glycolysis when ATP is produced from the breakdown of 1,3-BPG and PEP
Do eukaryotes and/or prokaryotes undergo ETC? If both, what is the difference between eukaryotic and prokaryotic ETC?
Both eukaryotes and prokaryotes perform the Electron Transport Chain; They differ in the location of the ETC (Eukaryotes = mitochondrial membrane, Prokaryotes = Cell Membrane)
What is the precursor molecule to Isocitrate?
The precursor molecule of Isocitrate is cis-aconitate
What is the role of Citrate Synthase? How do NADH and ADP act as regulatory molecules to Citrate Synthase in the Krebs cycle?
Activation of Citrate Synthase increases the production of citrate and subsequently, cis-aconitate (Catalyzed by Aconitase) ————————————- NADH: Inhibitor of Citrate Synthase, ADP: Activator of Citrate Synthase
What is the function of Allolactose?
Allolactose binds to repressor, causing it to dissociate from the operator region
What are three types of noncoding RNA?
Three types of noncoding RNA include tRNA, siRNA, and miRNA
What is cDNA? How is it made?
cDNA does not include introns! cDNA = complentary to mRNA (introns have been spliced out following transcription; reverse transcriptase used to make cDNA)
What is the charge of DNA and why? Explain the apparatus for gel electrophoresis, specifically the charge of the apparatus.
DNA molecules are negatively charged, so they move towards the anode. Apparatus works like electrolytic cell (Negative cathode, Positive anode)
Explain what each type of Blotting is used for: Southern, Western, Northern
Southern = DNA, Western = proteins, Northern = RNA
What are ddNTPs?
Dideoxynucleotide Triphosphates (ddNTP) are nucleotides that lack an OH group at both the 2’ and 3’ carbons
What is Acetylation? What is the effect of increasing Acetylation on the overall rate of gene transcription?
Acetylation removes a positive charge on Lysine residues in histone proteins, decreasing the level of attraction between + charged histones and - charged DNA backbone –> Creates space between histone and DNA, making gene transcription easier
What are the structures of all 4(5) nucleotides?
Structures of nucleotides!
Describe the flow of ions across the cell membrane during the peak of an action potential.
Peak of action potential = Na not flowing, K flowing out
What is the specialized part of a neuron where action potentials are summated?
Action potentials are summated at a specialized part of a neuron called the Axon hillock
What are the functions of the following brain regions: Temporal lobe, basal ganglia, inferior colliculus?
*Temporal Lobe = Houses auditory cortex and processes auditory info *Basal Ganglia = Controls fine motor movement *Inferior colliculus = Part of auditory pathway that transmits signals to medical geniculate nucleus located within the thalamus
What are Efferent nerves responsible for?
Efferent nerves = Responsible for carrying out reflexive action (Ex: Extension of leg)
What are the resident macrophages of the CNS?
Microglia are a type of glial cell that function as the resident macrophages of the CNS
Which neurotransmitter is crucial to muscle contraction?
Acetylcholine (ACh) = Neurotransmitter released by somatic neurons in order to induce muscle contraction
What are Nociceptors? Are they Afferent or Efferent? Sensory or Motor?
Nociceptors are neurons that convey sensations of pain to the CNS –> These neurons are Sensory and Afferent
Which of the following induce changes in how stimuli are encoded via effects on gene expression: Steroid Hormones, Peptide Hormones, Methylation?
Steroid Hormones and Methylation can affect gene expression (Steroid Hormones = Bind with nuclear receptors that regulate expression through transcription factors, Methylation = DNA-level covalent modification that is an example of epigenetics) ———————————————— Peptide Hormones do not affect gene expression (Peptide Hormones = Bind to membrane receptors and trigger intracellular signaling cascades that impact cellular activity)
During periods of extended fasting, free fatty acids are converted to what? Where are these molecules used?
During periods of extended fasting, free fatty acids are converted to ketone bodies, which may be utilizes by neurons via the TCA cycle
Which fatty acid derivative prevents the loss of water from the leaves of plants? Why?
Biological waxes are fatty acid derivatives that prevent the loss of water from their leaves (long-chain fatty acids esterified to long-chain alcohols –> Hydrophobic and used as waterproofing)
What is Enzymatic Promiscuity?
Enzymatic Promiscuity refers to the case in which a single enzyme can exercise catalytic effects on a wide variety of structurally diverse substrates (not highly specific)
What role does each of the following play in the transport of Cholesterol: VLDL, HDL, Chylomicrons, LDL?
LDL= Maojr transporter of cholesterol to the tissues of the body; HDL = also transports cholsterol, but brings it to the liver; Chylomicrons and VLDL = Primarily transport triglycerides
Which enzymes catalyzes breakdown of fatty acids and throuh what mechanism? Where is this enzyme expressed?
Hormone-sensitive Lipase is highly expressed in adipose tissues and steroidogenic tissues (adrenal cortex, ovaries, testes) –> This lipase catalyzes the breakdown of triacylglycerols to fatty acids and glycerol through the hydrolysis of ester linkaes
How would removing the anterior pituitary gland affect tropic hormones and their function?
Anterior pituitary gland secretes vital Tropic Hormones, one of which is Thyroid-stimulating Hormones (TSH) –> TSH increases the basal metabolic rate
What type of Steroid hormone is Aldosterone? What are the effects of Aldosterone on sodium, potassium, and water?
Aldosterone is an adrenal mineralocorticoid –> Acts on distal tubules and collecting ducts of nephrons to stimulate Na retention, water retention, and K secretion
All of the followin act as second messengers EXCEPT: cAMP, ATP, cGMP, Calcium ions
Calcium ions, cAMP, and cGMP are common secondary messengers
How do Steroid and Peptide hormones induce physiological effects, respectively? Timing?
Steroid Hormones = Pass through plasma membrane and affect gene transcription (Longer-lasting) ———————————- Peptide Hormones = Act through more rapid second messenger pathways
What are the 4 types of Pancreatic cells and what are their functions?
Alpha cells = Produce glucagon, Beta cells = Produce insulin (Type 1 diabetes), Delta cells = Produce somatostatin, Epsilon cells = Produce Ghrelin
Where are CRH and ACTH secreted, respectively? What is the function of ACTH?
*CRH = Secreted by the hypothalamus *ACTH = Released by anterior pituitary gland, Acts on adrenal cortex to release cortisol
What is the physiological effect of Insulin?
Insulin does all of the following: 1) Stimulates glycogenesis (Glycogen synthesis) 2) Increases triglyceride synthesis 3) Decreases fatty acid oxidation (store sugars rather than break down fats for energyg use) 4) Facilitates uptake of glucose into cells, resulting in reduced blood glucose levels
What is the function of Luteinizing Hormone? In males and females?
*Females = Luteinizing Hormone causes mature follicles on the ovaries to undergo ovulation (11-21 days of menstrual cycle) *Males = LT binds to receptor on Leydig cells and stimulates Testosterone synthesis and secretion
What is the correct ejaculatory pathway of sperm?
SEVEN UP = Seminiferous tubules, Epididymis, Vas deferns, Ejaculatory ducts, Nothing, Urethra, Penis
