Important Enzymes and Intermediates

Question 1

Hexokinase

Answer 1

Glucose to Glucose 6-P in Glycolysis 
Slow 
Low Vmax and Km
In all cells 
Uses ATP

Question 2

Glucokinase

Answer 2

Glucose to Glucose 6-P in Glycolysis 
Fast
Only in liver and kidney 
High Vmax and Km
Uses ATP

Question 3

Glut 4 tansporter

Answer 3

Insulin Sensitive

Question 4

Glut 2 Transporter

Answer 4

NON-insulin sensitive
Only in brain, liver and pancreas
(Brain and liver need to be able to take up glucose all of the time. And the pancreas needs to be able to “sense” glucose even without insulin so it does its freaking job)

Question 5

Phosphofructokinase-1

Answer 5

Enzyme for Fructose 6-p to Fructose 1,6 PB
RATE LIMITING STEP FOR GLYCOLYSIS
Consumes ATP
Allosterically regulated
Ex: High glucose/High insulin&raquo_space; decreased cAMP&raquo_space; decreased protein kinase A&raquo_space; activated PFK2&raquo_space; increases Fructose 2,6 PB&raquo_space; stimulates PFK1!!!!

PFK1 is downregulated by ATP and citrate (both from TCA cycle) and upregulated by AMP, F2,6BP

Question 6

Pyruvate kinase

Answer 6

Enzyme for PEP to Pyruvate.

Creates 2 ATP (4 per glucose molecule)

Question 7

Lactate dehydrogenase

Answer 7

Enzyme for Pyruvate to Lactate.

Uses NADH to create NAD+, which can be used in glycolysis

Question 8

Pyruvate dyhydrogenase

Answer 8

Enzyme for Pyruvate to Acetyl CoA

Relies on Thiamine as a cofactor (people who only consume alcohol don’t have this enzyme – difficulties creating acetyl CoA and all the stuff that follows)

Question 9

What are the steps you need to know in Glycolysis (intermediates)?

Answer 9

Glucose&raquo_space; Glucose6-P&raquo_space; Fructose 6-P&raquo_space; Fructose 1,6-P&raquo_space;&raquo_space; PEP&raquo_space; Pyruvate&raquo_space; Acetyl CoA OR Lactate

Question 10

Glucagon

Answer 10

Think of it like “hungry insulin”… released during fasting.
PHOSPHORYLATES
Promotes gluconeogenesis

Question 11

Insulin

Answer 11

Released in presence of glucose (fed state)
Promotes glycolysis
DE-phosphorylates

Question 12

What are the steps (intermediates) of the TCA cycle

Answer 12

Pyruvate&raquo_space; Acetyl CoA&raquo_space; Citrate&raquo_space; alpha ketogutarate&raquo_space; Succinate&raquo_space; Fumarate&raquo_space; L-malate&raquo_space; Oxaloacetate

Question 13

Products of TCA cycle

Answer 13

NADH
FADH
GTP
CO2

Question 14

Where do amino acids enter the TCA cycle?

Answer 14

alpha-ketoglutarate

Succinate

Question 15

Pyruvate carboxylase

Answer 15

Enzyme for Pyruvate to Oxaloacetate in gluconeogenesis

Uses 2 ATP

Activated by high Acetyl CoA

Question 16

PEPCK

Answer 16

Enzyme for Oxaloacetate to PEP in gluconeogenesis

Uses 2 GTP

Question 17

Fructose 1,6 bisphosphatase

Answer 17

Enzyme for Fructose 1,6 BP to Fructose 6-P in gluconeogenesis

Question 18

Glucose 6 phosphatase

Answer 18

Enzyme for Glucose 6-P to Glucose in gluconegenesis

Question 19

What are the main steps (intermediates) in gluconeogenesis?

Answer 19

Pyruvate&raquo_space; Oxaloacetate&raquo_space; PEP&raquo_space;&raquo_space;Fructose 1,6PB&raquo_space; Fructose 6P&raquo_space; Glucose 6 P&raquo_space; Glucose

Question 20

Precursors for Gluconeogenesis

Answer 20

Lactate: generated in skeletal muscle. Lactate can be converted to pyruvate

Amino Acids: provide carbon skeletons to the TCA, which results in the production of glucose via oxaloacetate

Glycerol: Released during hydrolysis of trigylcerides in adipose. Bypasses PEP and continues from there. Enters cycle as Glyceraldehyde 3-P

Question 21

Where in the cell, and in which organs, does gluconeogenesis take place?

Answer 21

Cytosol of liver (and kidneys)

Question 22

Glycogen

Answer 22

A storage form of glucose, mainly in muscle and liver

Glycogenesis (Synthesis): Occurs in well-fed state. Key enzyme in glycogen synthase. Branching enzyme. Insulin dephosporylates glycogen synthase (activating it) which inhibits glycogen breakdown.

Glycogenolysis (Breakdown): Occurs in fasting state. Key enzyme is glycogen phosphorylase. De-branching enzyme. Activated by glucagon in liver or epinephrine. Phosphorylates glycogen phosphorylase.

Question 23

Fatty acid synthase

Answer 23

Enzyme in fatty acid synthesis that converts Malonyl CoA to Fatty acid

Question 24

Acetyl CoA carboxylase

Answer 24

Enzyme in fatty acid synthesis that converts Acetyl CoA to Malonyl CoA. Is the RATE LIMITING STEP

Question 25

Malonyl CoA

Answer 25

What finally "becomes" fatty acid during synthesis. Is and INHIBITOR of the carnitine shuttle, used in fatty acid breakdown (B-oxidation)

Question 26

Citrate Shuttle

Answer 26

In the mitochondrial membrane Fatty acid synthesis Acetyle CoA in the mitochondria to OUT into the cytoplasm

Question 27

Basic steps of fatty acid synthesis

Answer 27

Acetyle CoA (in mitochondria) >> Citrate Shuttle >> Acetyl CoA in cytoplasm >> Malonyl CoA >> Fatty acid

Question 28

Fatty acid elongation and desaturation

Answer 28

Elongation takes place in the ER and the mitochondria | Desaturation takes place in the ER

Question 29

Fatty acid CoA synthase

Answer 29

Enzyme that converts Fatty Acid CoA to Aycl CoA in Fatty Acid breakdown (beta oxidation)

Question 30

Acyl CoA Dehydrogenase

Answer 30

Enzymes that converts Acyl CoA to Acetyl CoA in fatty acid breakdown (beta oxidation)

Question 31

Basic steps in Fatty Acid breakdown (Beta oxidation)

Answer 31

Fatty acid in cytoplasm >> Acyl CoA >> Carnitine Shuttle >> Acyl CoA in mitochondria >> Acetyl CoA

Question 32

What are ketone bodies and how do they get into your blood?

Answer 32

In Diabetes (hyperglycemia) all of the oxaloactetate is being used in gluconeogensis (hence the hyperglycemia). With OAA to help run the TCA cycle, Acetyl CoA will be used to make ketone bodies to help "feed" the muscles and brain Also, if you are reallllly hungry, your liver will start breaking down the fatty acids. During this time, your body is probably also still trying to do gluconeogenesis. Regardless, ketones are made via fatty acid breakdown in order to got the brain and muscles for fuel, where ketones will be reconfigured into the much-desired Acetyl CoA

Question 33

HMG CoA reductase

Answer 33

RATE LIMITING STEP in cholesterol synthesis | Stimulated by insulin

Question 34

HMG CoA

Answer 34

Cholesterol synthesis

Question 35

Mevalonate

Answer 35

Cholesterol synthesis

Question 36

Squalene

Answer 36

Cholesterol synthesis

Question 37

What is consumed in Cholesterol synthesis

Answer 37

NADPH >> NAD

Question 38

Lipoproteins

Answer 38

Apolipoprotein + (Cholesteol or Triglycerides or Phospolipids) VLDL, IDL, LDL, HDL

Question 39

Pancreatic Lipase

Answer 39

In intestine, degrades triglycerides into Free Fatty Acids

Question 40

Lipoprotein Lipase (LPL)

Answer 40

Found in vascular epithelium in adipose and muscle cells. Tryglycerides >>> free fatty acids

Question 41

Hepatic Triglyceride Lipase

Answer 41

Degrades IDLs into LSL

Question 42

Hormone Sensitive Lipase

Answer 42

Intracellular; Degrades TGs in adipose cells

Question 43

Apolipoprotein E

Answer 43

Mediates remant uptake in liver | Chylomicron, Chylomicron remnant, VLDL, HDL

Question 44

What amino acid can modestly increase dTMP levels in the setting of folate deficiency

Answer 44

Thymidine

Question 45

De novo synthesis of pyrimidines requires what amino acid(s)?

Answer 45

Aspartate

Question 46

De novo synthesis of purines requires what amino acid(s)?

Answer 46

Aspartate, glycine, glutamine, | And THF