Signal Transduction, Glycolysis, TCA Cycle And Electron Tansport Chain

Question 1

What are the general steps of signal transduction?

Answer 1

1. Signals
2. Receptors
3. Signal Amplification
4. Cellular Response
5. Signal Termination

Question 2

What are the two outcomes of signal transduction pathways?

Answer 2

1. Change the activity of an enzyme or group of enzymes

2. Increase or decrease gene expression

Question 3

What are the signals in signal transduction?

Answer 3

• hormones and growth factors
• neurotransmitters
• smells
• taste sensations
• light
• extracellular matrix

Question 4

Adenylate Cyclase

Answer 4

• activated by the G-alpha subunit
• produces cAMP from ATP
• a part of the GPCR: epinephrine of glucagon cascade

Question 5

cAMP

Answer 5

• produced by adenylate cyclase
• 2nd messenger
• activates protein kinase A (PKA)

Question 6

PKA

Answer 6

• activated by cAMP

- PKA phosphorylates a number of metabolic enzymes

Question 7

Phospholipase C (PLC)

Answer 7

• activated by G-alpha unit in GPCR: vasopressin or oxytocin cascade
• cleaves PIP2

Question 8

PIP2

Answer 8

GPCR: Vasopressin or Oxytocin Cascade
- cleaved by PLC
- produces two 2nd messengers: DAG and IP3
GPCR: Insulin Cascade
- PIP2 is phosphorylated by PI-3-Kinase to give PIP3
- there is no cleavage of PIP2 and no 2nd messengers

Question 9

DAG

Answer 9

• produced by PIP2
• remains in the membrane (hydrophobic)
• activates Protein Kinase C (PKC) when coupled with Ca+ triggered by IP3

Question 10

IP3

Answer 10

• produced by PIP2
• diffuses away from the membrane
• binds to IP3 receptor located in ER membrane
• IP3 receptor is a gated channel for Ca+ release

Question 11

PKC

Answer 11

• phosphorylates a number of enzymes, many involved in growth control

Question 12

IRS - 1

Answer 12

• binds to phosphorylated receptor (self-phosphorylated, no G protein involved)
• phosphorylated by the receptor

Question 13

PI-3-Kinase

Answer 13

• binds to phosphorylated IRS-1

Question 14

PIP3

Answer 14

• produced by the phosphorylation of PIP2 by PI-3-Kinase

Question 15

PDK-1

Answer 15

• binds to PIP3 and becomes active

- phosphorylates Akt

Question 16

Response to GPCR: Epinephrine or Glucagon Cascade

Answer 16

Glycogen and triglycerides broken down to provide energy for the body

Question 17

Response to GPCR: Vasopressin or Oxytocin Cascade

Answer 17

PKC phosphorylates a number of enzymes, many involved in growth control

Question 18

Response to RTK: Insulin Cascade

Answer 18

Glucose transporters in skeletal muscle and adipose tissue are brought to the plasma membrane to transport glucose into the cell where it can be stored as glycogen (muscle) or synthesized into triglycerides

Question 19

Integration

Answer 19

• two hormones can work together or oppose one another in a pathway
• metabolic pathways can be linked together through a common hormonal signal

Question 20

Adenylate Kinase

Answer 20

• maintains ATP levels in equilibrium

2 ADP ATP + AMP

Question 21

Glucokinase/Hexokinase

Answer 21

• regulates the 1st step of glycolysis, phosphorylation of glucose into glucose 6-phosphate

Question 22

PFK-1

Answer 22

• regulates the 3rd step in glycolysis, phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate
• very important because it regulates the rate-limiting step