Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
|
What are the high affinity glucose transporters? What speed do they work at? What tissues?
|
High affinity transporters: GLUT 3, 4
They work at high speed all the time. (Glut 3-neurons, placenta, testes. Glut 4- muscle and adipose tissue) |
|
|
What are the low affinity glucose transporters? What speed do they work at? What tissues?
|
GLUT 1-ubiquitous, esp in RBC
GLUT 2- liver, beta cells, sm intestine, kidney. Their speed depends on the glucose concentration. Increased glucose, increased speed. |
|
|
What three characteristics make glucose transport different than non facilitated transport
|
Speed and specificity, saturation kinetics, and susceptibility to competitive inhibition.
|
|
|
Name the tissues that the different GLUT proteins operate in. What is the relative affinity/Km of each (high/low)
|
GLUT 1-ubiquitous, especially in RBC (low affinity, high km)
GLUT 2- liver, beta cells, small intestine, kidney (low affinity, high Km) GLUT 3- neurons, placenta, testes (high affinity, low Km) GLUT-4-muscle and adipose (high affinity, low Km) |
|
|
What does a low Km mean? What does it mean for glucose uptake and the role of insulin?
|
High affinity. Glucose uptake is the rate limiting step. Found in insulin dependent cells. (on page 116)
High affinity (liver cells) means that transport changes linearly with the blood glucose concentration. Lots of blood glucose=uptake, low blood glucose=eflux |
|
|
What is the first step of glycolysis? Is it reversible? Why or why not?
|
Phosphorylation of glucose. This traps the glucose molecules inside the cell. This REQUIRES ATP. It is irreversible because of the high negative delta G.
|
|
|
Where is hexokinase found? Glucokinase? What is metabolic coupling?
|
Hexokinase- most cells, broad specificity
Glucokinase-ONLY in liver parenchymal cells and Pancreatic beta cells. Coupled metabolism means that a high affinity transporter works with a high affinity hexokinase. |
|
|
Where do you find low affinity hexokinase? What inhibits hexokinase?
|
Low affinity hexokinase is found in the brain and muscle cells and allow them to have first call on glucose when supply is limited.
Hexokinase is inhibited by GLUCOSE-6-PHOSPHATE |
|
|
What is special about glucokinase?
|
Higher Km means that when there is an increase in the blood glucose concentration, the rate of glucose uptake also increases. It allows the liver to adjust the amount of glucose stored as glycogen.
|
|
|
Describe the features of the committed step of glycolysis.
|
Catalyzed by PFK-1
-Rate limiting step. -Requires ATP -allosteric control -Irreversible -highly regulated -there is an addition of a phosphate at the 1 carbon |
|
|
Describe the positive and negative regulators of PFK-1. Why does this make sense?
|
NEGATIVE: ATP, citrate, PEP
POSITIVE: AMP, fructose-6-phosphate, fructose-1,6-bisphosphate, fructose-2,6-bisphosphate. The negative regulators are products of glycolysis, and the positive regulators are substrates and end product of PFK-1 reaction. |
|
|
What steps of glycolysis require ATP?
|
PFK-1 and phosphorylation of glucose
|
|
|
When does the "reward phase" of glycolysis start?
|
at glyceraldeyde-3-phosphate
|
|
|
What happens in the glyceraldehyde-3-phosphate to 1,3-BPG reaction?
|
It's the first oxidation/reduction reaction. NADH is produced, Pi is added. This is an example of coupled oxidation phosphorylation.
|
|
|
When is the net ATP yield zero in glycolysis?
|
After the production of 3-phosphoglycerate. This is substrate level phosphorylation.
|
|
|
What does phosphoglycerate mutase do?
|
Shifts the phosphate group from C3 to C2. The intermediate is 2,3-BPG
|
|
|
In what process is 2,3-BPG found and in what cells is it abnormally high?
|
It is an intermediate in the phosphoglycerate mutase. Very high in erythrocytes-detour from the glycolytic pathway using bisphosphoglycerate mutase and 2,3-BPG phosphatase. The oxygen affinity of hemoglobin is mediated by 2,3 BPG which stabilizes the de-oxy state.
|
|
|
What kind of reaction is carried out by enolase?
|
dehydration
|
|
|
Under what conditions is pyruvate kinase induced?
|
High carbohydrate and high insulin. well fed individual has a better capacity to metabolize carbs
|
|
|
Where does substrate level phosphorylation take place
|
in the pyruvate kinase step (production of kinase) and 3-phosphoglycerate kinase.
|
|
|
What steps act as controls in glycolysis?
|
Pyruvate kinase step and PFK-1.
|
|
|
What steps of glycolysis produce ATP?
|
3-phosphoglycerate kinase and pyruvate kinase (same as substrate level phosphorylation)
|
|
|
What step produces NADH? What does it require?
|
Step carried out by GADP and requires an inorganic phosphate. The P gets added and produces 1,3-BPG
|
|
|
When does lactate dehydrogenase activity act?
|
When there is not enough oxygen to regenerate NAD+. Used in "step 11" pyruvate to lactase
|
|
|
What happens in glycolysis in RBC?
|
Even under aerobic conditions glycolysis always terminates in lactate because the mitochondria which are required for aerobic respiration are not present. They synthesize and degrade 2,3 BPG-they have a much greater concentration of 2,3 BPG than other cells
|
|
|
What tissues normally derive energy from glycolysis and produce lactate?
|
Brain, GI tract, renal medulla, retina, and skin.
|
|
|
When does lactic acidosis usually occur?
|
When there is a circulatory system collapse and O2 cannot get to cells. There is no more oxidative phosphorylation and they get energy anaerobically.
|
|
|
What is the overall production of ATP in aeorobic glycolysis?
|
+8 ATP. Loose 2 in the phosphorylative and PFK-1 step. then you generate 2 NADH (3 each) and finally one in each sub phosphorylation step.
|
|
|
Where is NAD+ produced?
|
Through oxidative phosphorylation in the Mitochondria. In lactate production "step 11"
|
|
|
What step does glucose cleavage happen?
|
Aldolase
|
|
|
How many ATP are generated in anaerobic respiration?
|
2 because there is no NADH production. -2 from the first two steps, and +2*2 because of pyruvate kinase and phyroglycerokinase.
|
|
|
where is the only redox reaction in glycolysis?
|
glyceraldehyd 3 phosphate to 1,3 BPG
Pi added is coupled to oxidation |
