Integration of Metabolism

Question 1

what is the fed state metabolism controlled by?

Answer 1

• insulin

- pancreas sends insulin to liver, brain, and adipose tissue

Question 2

how is glucose transferred between blood and tissue

Answer 2

• facilitated diffusion

Question 3

where does glucose go first after it enters bloodstream and how (2)

Answer 3

• liver

- via portal vein

Question 4

glycolysis

Answer 4

glucose -> pyruvate -> acetyl-CoA

Question 5

what tissues pick up glucose (4)

Answer 5

• liver, brain, adipose tissue, muscle

Question 6

how happens to extra glucose (2)

Answer 6

• stored in muscle and liver as glycogen

- converted to acetyl-CoA in liver for FA synthesis

Question 7

where do proteins go first from the bloodstream and how? (2)

Answer 7

• liver

- via portal vein

Question 8

what are amino acids used for in liver and other tissues

Answer 8

• protein synthesis

Question 9

what happens to extra amino acids in liver?

Answer 9

• broken down to alpha-ketoacids and NH3

Question 10

what happens to NH3 in the liver

Answer 10

• converted to urea in urea cycle

Question 11

what happens to carbon skeletons (alpha-ketoacids) in the liver

Answer 11

• eventually converted to acetyl-CoA and used in FA synthesis

Question 12

what happens to some AA if carbs are low

Answer 12

• some AA used for gluconeogenesis

Question 13

gluconeogenesis

Answer 13

pyruvate -> glucose

Question 14

what is the first step in digesting lipids

Answer 14

• emulsify them using bile to form micelles

Question 15

what happens to emulsified lipids (TAG)

Answer 15

• broken down by intestinal lipases into MAG and 2FA to be absorbed by intestinal cells

Question 16

chylomicron (3)

Answer 16

• lipoprotein particles made up of TAG, apolipoproteins, and some cholesterol esters
• transports dietary TAG to adipose tissue
• remnants containing cholesterol are delivered to liver

Question 17

what happens to MAG and 2 FA in the intestinal cells?

Answer 17

• reassembly into TAG and then into chylomicrons

Question 18

fate of chylomicrons (2)

Answer 18

1. released from intestinal cells to lymphatic system

2. eventually merge into bloodstream and is distributed among tissues to be used for energy or stored

Question 19

lipoprotein lipase function

Answer 19

• breaks down TAG into MAG and 2 FA in tissues

Question 20

very low density lipoprotein (VLDL)

Answer 20

• transport of endogenous TAGs to adipose tissue via circulation

Question 21

how is cholesterol synthesized and where

Answer 21

• liver synthesizes cholesterol from acetyl-CoA

Question 22

low density lipoprotein (LDL) (3)

Answer 22

• used to deliver cholesterol to tissue
• picked up by tissue via receptor mediated endocytosis
• high LDL = atherosclerosis

Question 23

high density lipoprotein (HDL) (3)

Answer 23

• carried extra cholesterol from tissues back to liver
• known as good cholesterol: high HDL = lower risk of atherosclerosis
• pick up by liver via endocytosis

Question 24

what is the fasting state metabolism controlled by (2)

Answer 24

• glucagon

- pancreas releases glucagon to the liver

Question 25

what is the order of molecules used during fasting state?

Answer 25

• free glucose, glycogen, FAs stored in adipose tissue

Question 26

how is glycogen used during fasting state

Answer 26

• converted to free glucose in bloodstream

Question 27

what does hormone sensitive lipase released by glucagon do

Answer 27

• break down TAG completely into glycerol and 3 fatty acids

Question 28

what happens to free FAs during fasting state

Answer 28

• complexed with albumin and delivered to tissues (excluding brain)

Question 29

how is glucose synthesized during fasting state

Answer 29

• gluconeogenesis in liver from glucogenic AAs and propionyl-CoA

Question 30

what happens during prolonged fasting (2)

Answer 30

• acetyle-CoA cannot enter TCA cycle because OAA is being used for gluconeogenesis
• acetyl-CoA converted to ketone bodies and released to bloodstream to be used for energy by brain and heart