Exam 3 – Dr. Sullivant Carbohydrate Metabolism Flashcards
What are the body’s energy sources?
Food intake (CHOs, fats, proteins)
Metabolism
ATP
Why is metabolism important?
All cells and tissues must have energy for survival/homeostasis, growth, reproduction, repair, and movement
What is the main energy source used by the body?
ATP
Where is ATP present?
In cytoplasm and nucleoplasm of all cells
What is ATP a combination of?
Adenine
Ribose
3 phosphate radicals
What is ATP obtained from?
CHO, proteins, and fats
Where does the important stuff/magic happen in ATP?
In phosphate radicals
What does the breaking of a phosphate molecule from ATP do?
Causes a band of energy release, which powers muslce
Why does ATP provide so much energy?
High energy bonds
Removal of each of the last 2 phosphate radicals liberates 12,000 calories of energy
ATP is involved in energy utilization. What does it do?
Active ion transport
Muscle contraction
Synthesis of molecules
Cell division and growth
ADP and Pi are involved in energy production. What do they do?
Help proteins, CHOs, and fats that are involved in oxidation
What do kinases do?
Add a phosphate
What do phosphatases do?
Remove a phosphate
What does phosphorylase do?
Splits a compound by adding phosphate
What are 90% of CHOs in the body used for?
ATP production
What are the final products of CHO digestion in the gut?
Fructose
Galactose
Glucose (80%)
What happens after fructose and galactose absorption from the GI tract?
They are rapidly converted to glucose in the liver via glucose phosphatases; therefore, glucose is the final common pathway for transport/supply of CHO to all tissues
What is option 1 for the fate of glucose in the liver?
CHO is processed in the liver, then glucose formation, then transport out of liver to needy tissues for energy use
- Glucose has to go through a cell membrane
- Glucose foes through a series of reactions inside the cell to produce ATP (glycolysis, TCA)
- Hydrogen atoms that are released concurrently yield even more ATP (glycolysis, TCA)
What is option 2 for the fate of glucose in the liver?
CHO processed in the liver, then glucose formation, the glycogenesis (energy storage)
What is glycogen?
A large polymer of glucose
What is option 3 for the fate of glucose in the liver?
Glycogenolysis in the liver
What is glycogenolysis?
Breakdown of stored glycogen in times of energy needs
What produces ATP?
Glucose entry into the cell Glycolysis Citric acid cycle Chemiosmotic mechanism Pentose phosphate pathway Glycogenesis Glycogenolysis
Glucose is too large to pass through cell membranes. What allows it pass?
Facilitated diffusion
How does facilitated diffusion allow glucose to move into most cells?
A specialized “carrier protein” in the cell membrane binds with glucose
Glucose transporter “GLUT” are on the outside and release it intracellularly
Glucose moves from an area of high concentration to lower concentration
What is insulin?
An anabolic hormone secreted by pancreatic β cells
What does insulin do?
Speeds the process of facilitated diffusion, which makes it a more effective and efficient process
Where can glucose transport occur without insulin?
RBC
Brain
Liver
What is the rate of CHO utilization by most cells controlled by?
Rate of insulin secretion
Look at figure 67-3
Look at figure 67-3
What is a GLUT 1 transporter?
RBCs
What are GLUT 2 transporters?
Liver
Pancreas
GI tract
Kidney
What is a GLUT 3 transporter?
Brain
What are GLUT 4 transporters?
Muscle
Fat
What is the first step once glucose is in the cell?
It must be “locked” in the cell
Phosphorylation via glucokinase or hexokinase
Glucose becomes Glucose 6 phosphate via glucokinase and ATP
What is glycolysis?
The splitting of glucose to form 2 pyruvic acids molecule
How does glycolysis occur?
Via 10 successive chemical reaction inside the cell
Does not require oxygen
What does phosphofructokinase (PFK) do?
Converts fructose-6-phoppate to fructose-1,6-diphosphate
What does ATP do to PFK?
Inhibits it
What does ADP do to PFK?
Activates it
What is the initial energy source for glycolysis?
Phosphofructokinase
What is the net gain of ATP from glycolysis?
2 ATP
What is the first step to using glucose for energy?
Conversion of pyruvic acid from glycolysis into 2 molecules of acetyl CoA
No ATP formed
4 H+ atoms released for later oxidation
What is the second step to using glucose for energy?
TCA cycle
Acetyl CoA is degraded into CO2 and H+ atoms in the mitochondria
Requires oxygen
What does the Kreb’s cycle start with? What does it produce?
Acetyl CoA
ATP
How many ATP are produced in the citric acid cycle?
2 (1 per Acetyl CoA)
What is the fate of hydrogen atoms?
Most combine with NAD+ to form NADH+
What will happen with NADH+?
It will enter into multiple oxidative chemical reaction that form lots of ATP
What is the 3rd step for using glucose for energy?
Oxidative phosphorylation
What is oxidative phosphorylation?
The oxidation of hydrogen atoms released from all the previous stages of glucose metabolism
How much of the ATP that comes from glucose metabolism is formed from oxidative phosphorylation?
90%
How many ATP come from oxidative phosphorylation?
30
List the amount of ATP and where they come from
Glycolysis: 2 TCA cycle: 2 Oxidative phosphorylation: 30 Total: 34 4 remaining H+ atoms go on to produce 4 more ATP Total: 38 per glucose molecule
Why does glycolysis occur?
As means to produce some energy when oxygen is low or unavailable
What is an alternative pathway for glucose?
Pentose phosphate pathway
What is the pentose phosphate pathway responsible for?
About 30% of glucose breakdown in liver and more in fat cells
What is the pentose phosphate pathway?
Cyclical process in which one molecule of glucose is metabolized per revolution of cycle
What does the pentose phosphate pathway yield?
CO2
H+ atoms
5 carbon sugar, D-ribulose
What can glucose be stored in? As what?
Liver and muscle as glycogen
How does glycogenolysis occur?
Via phosphorylation, catalyzed by enzyme phosphorylase
