New Quizzes/ HW Q's Flashcards
(30 cards)
a futile cycle is
when two opposing metabolic pathways are active at the same time
which of the following is false statement about ketone bodies
ketone bodies are used only by the brain
Pyruvate dehydrogenase uses a complex mechanism to convert pyruvate to acetyl-CoA. Which of the following is NOT a substrate, product or coenzyme in the pyruvate dehydrogenase reaction?
ATP
High intake of sucrose increases the risk of obesity because:
Fructose metabolism bypasses the highly regulated PFK-1 step in glycolysis
The initial reaction in glycolysis is NOT the commitment step because
Glucose-6-phosphate can be utilized in other pathways
Which of the following is NOT a fate of acetyl CoA in human?
precursor for glucose synthesis
Which of the following is FALSE regarding Nicotinamide coenzymes?
they act as prosthetic groups on enzymes
Which of the following is the reason why oxidation of FADH2 generates less ATP than oxidation of NADH in oxidative phosphorylation?
Oxidation of FADH2 occurs in complex II, bypassing one proton-pumping step across the inner mitochondrial membrane.
Which of the following statements is INCORRECT about the regulation of fatty acid synthesis?
Malonyl CoA inhibits fatty acid synthesis.
Brown adipose tissue is common in hibernating animals because of
they need to generate heat while energy need is low
Which of the following amino acids can be made from pyruvate via transamination reaction?
alanine
which of the following is not a fate of cholesterol in human
broken down to acetyl CoA through fatty acid oxidation
Which of the following lipoproteins has the role in reverse cholesterol transport?
HDL
Which of the following pairs is INCORRECT for the metabolite and its precursor amino acid?
serotonin from phenylalanine
which of the following is least soluble in water
cholesterol ester
You have just finished a carbohydrate-rich dinner and are hanging out on the couch watching football. Indicate in the table which metabolic enzymes are likely activated or inhibited in the liver. (pyruvate carboxylase, glucokinase, pyruvate kinase, glucose-6-phosphatase, and PFK-1)
pyruvate carboxylase- inhibited
glucokinase- activated
pyruvate kinase- activated
glucose-6-phosphatase- inhibited
PFK-1- activated
Explain why the first irreversible reaction in glycolysis is NOT the commitment step.
The resulting intermediate of the first reaction, glucose-6-phosphate, can
enter other pathways – gluconeogenesis, glycogen synthesis, pentose
phosphate pathway – and is not ‘committed’ to glycolysis
which enzyme mediates the commitment step of glycolysis
PFK-1
name one positive and one negative regulation mechanism of this enzyme
Positive: AMP or fructose-2,6-bisphosphate
negative: ATP, citrate or H+
Describe why high intake of sucrose (glucose + fructose disaccharide) increases the risk for obesity.
The majority of fructose metabolized in liver will bypass the highly regulated
PFK-1 step. Thus, energy state of the cell does not control fructose
metabolism. The propensity for fructose to be converted to glycerol, fatty
acids and triglycerides is very high and not as regulated
Anaplerotic reactions are used to add intermediates to the TCA cycle. The most important anaplerotic
reaction is mediated by the enzyme 1. Deficiency in this enzyme can be treated with 2, which gets
converted to the TCA cycle intermediate 3
- pyruvate carboxylase
- triheptonin
- succinyl-CoA
Explain why oxidation of FADH2 generates less ATP than oxidation of NADH in oxidative phosphorylation
FADH2 enters ETS in Complex III, while NADH enters in Complex I. FADH2
thus skips one proton-pumping step in ETS (4 H+), resulting in fewer H+ being
transported into the intermembrane space, and available for ATP synthesis.
Energy yield (bonus):
2.5 mol of ATP per 1 NADH – 10 H+
1.5 mol of ATP per 1 FADH2 – 6 H
between cholesterol and cholic acid which one is more soluble?
cholic acid is more soluble because it has extra hydroxyl groups and a carboxyl group
what does cholesterol structure look like
bland and only one OH group
