Overview of Carbohydrate Metabolism

Question 1

The concentration at which the reaction is half maximal is called the ________

Answer 1

Km.

Question 2

what is the rate limiting step in glycolysis

Answer 2

Fructose 6 phosphate conversion to Fructose 1,6 bis-phosphate by enzyme Phospho-Fructo-Kinase (PFK)

Question 3

The steps of glycolysis result in a net production of energy in the form of ATP and NADH which can be produced in the absence of _____ and _____

Answer 3

oxygen,

mitochondria

Question 4

Glycolysis is the main source of energy for which cells?

Answer 4

1) cells that do not have mitochondria (red blood cells) 2) tissues that have mitochondria but do not get enough oxygen (ischemic tissues, muscle during high intensity exercise)

Question 5

If sufficient oxygen is not present or the cell in question does not have mitochondria, pyruvate will be converted to _________ and exported from the cell.

Answer 5

lactate

Question 6

why is pyruvate converting to lactate and exported from the cell when oxygen isn’t present an important step?

Answer 6

This step is important because it regenerates the NAD from NADH which allows glycolysis to continue.

Question 7

When glucose is abundant in a liver cell, _________ predominates. When glucose is in short supply, _________ predominates.

Answer 7

glycolysis,

gluconeogenesis

Question 8

This reaction only occurs in liver and kidney (not muscle or adipose tissue)

Answer 8

glucose-6- phosphate to free glucose catalyzed by glucose-6-phosphatase

Question 9

This polymer of glucose (Glycogen) is synthesized from ________

Answer 9

glucose-6-P

Question 10

glycogen synthesis proceeds by adding individual glucose molecules in a _____ orientation.

Answer 10

1-4

Question 11

NADPH is a source of energy for which synthetic reactions?

Answer 11

fatty acid biosynthesis,
cholesterol biosynthesis,
defense against oxidative stress,
white cell function

Question 12

the pentose phosphate pathway (hexose monophosphate shunt) has what two main functions.

Answer 12

1) generate NADPH

2) generation of five carbon sugars (ribose) for use in nucleotide synthesis

Question 13

Name counter-regulatory hormones:

Answer 13

glucagon, catecholamines, growth hormone, and cortisol

Question 14

which pathways are active and suppressed, and which hormones are high and low Following a meal,

Answer 14

Insulin is high and counter-regulatory hormones are low. Glycolysis and glycogen synthesis are active and glucose is assimilated by peripheral tissues. Gluconeogenesis and glycogen breakdown are suppressed