Lecture Set 6

Question 1

What are 6 reasons for needing energy

Answer 1

mechanical work, synthesis, concentration work, electrical work, produce heat, bioluminescence

Question 2

Difference between photo and chemo trophs?

Answer 2

phototrophs fixate carbon into organic molecules, chemotrophs obtain carbon from eating

Question 3

What drives reactions?

Answer 3

oxidation –> releases energy, electron transfer

Question 4

How can unfavourable reactions be made favourable?

Answer 4

creating non-standard conditions (ex. siphoning off products to prevent equilibrium, create large enough gradient)
coupling with very favourable reaction (ATP-driven)

Question 5

What is the difference between equilibrium, steady state, and homeostasis

Answer 5

equilibrium is when deltaG=0
steady state is when deltaG doesn’t = 0 but there is no net movement
homeostasis are the regulatory mechanisms to maintain a dynamic steady state

Question 6

Describe enzymes

Answer 6

lower energy of transition state, work by conformational change when multiple weak interactions with active site, very specific

Question 7

What does Km represent?

Answer 7

affinity (low Km = higher affinity), concentration of substrate such that V=1/2 Vmax

Question 8

What are the different types of inhibition?

Answer 8

Reversible vs irreversible

competitive (doesn’t lower Vmax, changes Km) vs. noncompetitive (doesn’t change Km, lowers Vmax)

Question 9

Describe allosteric regulation

Answer 9

binding of molecule to non-active site, causing conformational change
can be positive (bind cAMP to protein kinase A) or negative (noncompetitive inhibition)

Question 10

How are enzymes regulated?

Answer 10

covalent modifications, compartmentalization, allosteric regulation, association with regulatory protein

Question 11

Describe phosphorylation

Answer 11

addition of phosphate group to hydroxyl group of serine, threonine or tyrosine
can have on/off or more/less effect depending on number of phosphorylation sites

Question 12

Describe regulation of glycogen

Answer 12

Glycogen can be regulated through either covalent modification or allosteric regulation (ATP, glucose, AMP)
glycogen phosphorylase breaks 1-4 bonds by inserting phosphate group. Phosphorylase has a (active) or b (inactive) forms, conversion between the two through phosphorylase b kinase and phosphorylase a phosphatase

Question 13

Describe how enzymes can be covalently modified

Answer 13

phosphorylated

cleavage –> synthesized in zymogen form, then cleaved to make active form

Question 14

What is the rest of the enzyme beside the active site used for

Answer 14

structural support
regulatory sites
interact with other proteins
substrate channels