Metabolism Overview Flashcards
4 characteristics of GLUT 2?
found in liver and pancreas
high Km
not responsive to insulin
cannot be saturated under normal conditions
3 characteristics of GLUT 4?
found in adipose tissue and muscles
low Km
stimulated by insulin (mvt of GLUT 4 to the membrane by exocytosis)
What is the normal glucose concentration in peripheral blood?
4-6 mM
Where does glycolysis take place?
cytoplasm
Does glycolysis require O2?
No
What are the products of glycolysis?
Pyruvate + 2 ATP + 2 NADH
Where is pyruvate converted to acetyl-CoA?
Mitochondria
What are the products of pyruvate conversion to acetyl-CoA?
1 Acetyl-CoA + 1 CO2 + 1 NADH`
Does pyruvate conversion require O2?
No
In what organs does glycogenesis and glycogenolysis occur? For what purpose?
Liver: maintain constant levels of glucose
Muscles: provide glucose to the muscle during exercise
Where do glycogenesis and glycogenolysis occur in the cell?
Cytoplasm
Do glycogenesis and glycogenolysis require O2?
No
Where does gluconeogenesis occur in the cell?
First step takes place in the mitochondria (pyruvate to oxaloacetate)
The rest of the reactions take place in the cytosol
In what organs does gluconeogenesis occur? For what purpose?
Liver and kidneys
To maintain blood glucose levels during fasting
Does gluconeogenesis require O2?
No
What is the energy source for glycogenesis?
UTP
What is the energy source for gluconeogenesis?
1 ATP + 1 GTP
What happens to acetyl-CoA once it is synthesized from pyruvate? 2 options
- If ATP is needed: entry into TCA
2. If there is enough ATP: fatty acid synthesis
What happens to pyruvate after glycolysis? 2 options
- If there isn’t enough acetyl-CoA: converted to acetyl-CoA
2. If there is enough acetyl-CoA: converted to oxoloacetate to enter gluconeogenesis
What happens to the 2 NADH produced by glycolysis? 2 options
- If O2/mitochondria are present: oxidized by ETC
2. If O2/mitochondria aren’t present: oxidized by fermentation
Where does the pentose phosphate pathway occur?
Cytoplasm
What does the PPP generate?
NADPH and sugars
What happens to NADPH after PPP? 3 options
- used for fatty acid synthesis
- bactericidal bleach in white blood cells
- acts as a reducing agent to maintain glutathione stores to protect against reactive O species
What happens to the sugars after PPP?
Nucleotide synthesis
What metabolic processes does insulin stimulate?
- PPP
- Glycolysis
- Fatty acid synthesis
- Glycogenesis
What are the 3 pathways to generate acetyl-CoA?
- Glycolysis and generation from pyruvate
- Fatty acid oxidation = beta oxidation
- From C skeletons of ketogenic amino acids, ketone bodies, and alcohol
Does the citric acid cycle require O2?
No, but it cannot occur without O2 being present, since it will be used by the ETC, which is the next step –> the citric acid cycle is an aerobic process!
Does the ETC require O2?
Yes
What are the products of the citric acid cycle?
3 NADH + 1 FADH2 + GTP + 2 CO2 + CoA-SH
What is another name for glycolysis?
Aerobic respiration
How much ATP does 1 NADH generate?
1.5 or 2.5 ATP
How much ATP does 1 FADH generate?
1.5 ATP
How much ATP does 1 GTP generate?
1 ATP
Is the electron transport of the ETC spontaneous or nonspontaneous?
Spontaneous = exergonic
What are the 2 transport mechanisms to bring NADH into the mitochondrial intermembrane space? How much ATP does each generate?
- Glycerol-3-phosphate shuttle: 1.5 ATP/1 NADH
2. Malate aspartate shuttle: 2.5 ATP/1 NADH
How do I know which NADH shuttle a cell uses?
More aerobic organs will use the most efficient one: malate-aspartate shuttle
Where does oxidative phosphorylation occur?
Mitochondrial inner membrane, generating ATP into the matrix
How does low O2 affect oxidative phosphorylation?
Inhibits it
How does low O2 affect the concentration of NADH and FADH2?
Increases! They accumulate because they cannot enter the ETC
How does low O2 affect the citric acid cycle?
Inhibits it to stop producing NADH and FADH2, which are already abundant
How do high levels of ADP affect the citric acid cycle?
Stimulates it
How does citric acid cycle activation affect the concentration of NADH and FADH2?
Increases them
What metabolic processes does glucagon stimulate?
- Gluconeogenesis
- Fatty acid beta-oxidation
- Ketolysis
- Glycogenolysis
Where does fatty acid synthesis occur in the cell?
Cytoplasm
Where does fatty acid beta-oxidation occur?
Mitochondria (and a little in the peroxisome)
Where does conversion from pyruvate to acetyl-CoA occur?
Mitochondria
Where does ketogenesis occur?
Mitochondria
When does ketogenesis occur?
When acetyl-CoA accumulates in the fasting state
Where does ketolysis occur?
Mitochondria
What does ketolysis generate?
Acetyl-CoA