Bio/Biochem Flashcards
Which sequence is Palindromic? A) 5’—GAACGTTC—3’ B) 5’—TATAAA—3’ C) 5’—TAGTTGAT—3’ D) 5’—GCGCCC—3’
DNA palindromes read the same from 5’-to-3’ on one strand as they do from 5’-to-3’ on the complementary strand.
For choice A, 5’—GAACGTTC—3’ is the reference strand, and the compliment to that strand is 3’—CTTGCAAG—5’. When the complementary sequence is read from 5’-to-3’ it is identical, making the sequence shown in choice A an example of a palindrome.
What are some characteristics of Ribosomes?
- They are composed of two subunits: one large and one small
- They bind tRNA molecules during translation
- They are composed of both rRNA and proteins
When a Sodium ion flows into a cell down its electrochemical gradient, will ΔG be positive or negative? How is Entropy affected?
Moving down the concentration gradient occurs spontaneously, therefore the ΔG will be negative.
If there is a concentration gradient, the system is displaced from equilibrium. Equilibrium represents an entropy maximum, so if there is activity that moves the system toward equilibrium, as there is in this case, entropy must increase.
Describe a G-protein cascade when cAMP is involved:
1) Hormone binds to a receptor on the cell membrane
2) G-protein associated with the receptor is activated by the binding of the hormone
3) G-protein migrates through membrane to activate adenylate cyclase
4) Adenylate cyclase converts ATP to cAMP (second messenger)
5) cAMP activates protein kinases and thereby alters cell metabolism
Describe the Cori cycle.
During prolonged exercise, anaerobic glycolysis becomes the primary source of ATP with pyruvate being converted to lactate in order to regenerate necessary NAD+ (NADH is oxidized to NAD+).
Lactate is transported to the liver where it is converted to glucose and metabolized.
What is the primary function of the colon and the rectum?
The colon includes the rectum, anus, and the large intestine.
The function of the large intestine is to absorb (reclaim) water from the waste.
The primary function of the rectum and anus is to store and expel waste.
List characteristics of bacterium.
- Unicellular
- Prokaryotic
- Has a circular chromosome
- Reproduces via binary fission
- Have a cell wall but it is made of peptidoglycan, NOT chitin (fungi have cell walls made of chitin)
Explain Nondisjunction in Meiosis
Nondisjunction is the failure of chromosomes to separate during anaphase.
In meiosis, there are two divisions, and the consequences of nondisjunction are different in anaphase I vs anaphase II.
- In anaphase I, the homologous pairs separate, so failure to separate during meiosis I would result in duplicated copies of both homologues in one cell. Therefore, two of the products of meiosis II would have too many chromosomes and two would have too few chromosomes. (either a trisomy or monosomy will result)
- If nondisjunction occurs in meiosis II however, the tetrads would still separate normally and the products of Meiosis I would be normal. This would result in half the daughter cells being normal and the other half having a problem with separation.
How does phosphorylation alter an enzyme’s function?
It creates a repulsive interaction that causes a conformational change in the enzyme.
Repulsive interactions, especially in a folded protein, would more likely be destabilizing.
What is Kd in enzyme kinetics and what does it mean when it increases/decreases?
Kd is the dissociation constant.
The higher the Kd for a pair of molecules, the more likely they are to dissociate, which is indicative of a weaker interaction.
Sometimes, binding thermodynamics data mention pK, which is the inverse log of Kd.
An increase in cholesterol has what impact on the plasma membrane?
Increased membrane fluidity at low temps and decreased fluidity at high temps.
At low temps, the membrane can become too rigid, but cholesterol interferes with close packing of the phospholipids.
At high temps, cholesterol stabilizes the membrane and raises its melting point.
