carbs (monosaccharides), lipids (fatty acids), proteins (amino acids)
Which nutrients provide us with energy?
acetyl CoA production, acetyl CoA oxidation, Electron transfer and oxidative posphorylation
What are the three main stages of Catabolism?
Separate metabolic pathways converge as acetyl-CoA is produced
Describe the first stage of catabolism
In Acetyl-CoA oxidation, the citric acid cycle removes electrons and produces NADH and FADH2. Very little ATP is formed.
Describe the second stage of catabolism
Electrons are transferred from NADH and FADH2 ultimately to O2. The final product is H2O which allows ATP to be produced. Accounts for 90% of cellular ATP production
Describe the third stage of catabolism
brain prefers glucose, quick energy, used in pentose phosphate pathway for nucleotide synthesis, synthesize structural polymers, stored as starch or glycogen for later
What are five reasons for why we need glucose?
Ingest food containing glucose, starch, glycogen, or disaccharides. Polysaccharides are broken down with amylase (salivary glands, pancreas). It is then transported through intestinal epithelial cells and into the bloodstream by wya of the liver.
How does glucose get into our bloodstream?
Occurs when the lactase activity of intestinal epithelial cells stop. Lactose cannot be digested or absorbed by the small intestine. In the large intestine, bacteria converts it into toxic products. It also increases the osmolarity of intestinal contents-- causing water retention.
Explain lactose intolerance
Na+glucose symporter is a secondary active transport that allows sodium and glucose to enter the epithelial cell. GLUT2 is a facilitated transport that moves glucose into the blood.
Describe the transport of glucose from intestinal lumen through the intestinal epithelial cells.
Glucose in the hepatic portal vein is transported into the hepatocyte by GLUT2. When in the liver, glucose can be converted to glucose-6-phosphate. G6P is used for glucose storage in the form of glycogen. G6P can be reconverted to glucose as regulated by the liver and GLUT2 transports glucose out of the hepatocyte and back into the bloodstream
Describe the transport of glucose through the liver.
Basal glucose uptake into nearly all mamalian cells through GLUT1 and GLUT3 that have a high affinity for glucose.
How does glucose get into the cell when levels are average?
Glucose is imported into the liver by GLUT2 (low affinity-release) to be synthesized into glycogen for storage. Glucose is imported into the pancrease by GLUT2 and insulin is secreted. Insulin increases number of GLUT4 receptors in muscle and adipose tissue. Muscle tissue converts glucose to glycogen and adipose tissue converts glucose to fat.
How does glucose get into the cell when levels are high?
The pancreas secretes glucagon into the bloodstream which causes the liver to break down stored glycogen. Glucose is exported from the liver through GLUT2
How does glucose get into the cell when levels are low?
Insulin increases glucose transporters which helps the body get glucose into the cells that need it (like muscles)
Why do some athletes illegally obtain and inject insulin?
GLUT2 is a secondary active transport (passive) so the direction of transport depends on the gradient that has been established.
What characteristic of GLUT2 allow it to work both as an importer and as an exporter?
It is a central pathway. Most intermediate serve as branch points to other metabolic pathways.
Why does glycolysis contain so many reactions?
It keeps the intracellular concentration of glucose low so that the cells are able to import more glucose. Phosphorylated sugars can't use the GLUT transporters (trapped in cell). Some intermediates will transfer the P back to ADP to form ATP. Phosphorylation also provides more of a "hook" for the enzyme active site, leading to increased specificity
What are four reasons for the phosphorylation of glucose during glycolysis?
Glucose + ATP > glucose 6-phosphate + ADP, Fructose 6-phosphate + ATP > fructose 1,6-bisphosphate + ADP, Phsphoenolpyruvate + ADP > pyruvate + ATP
What are the three irreversible reactions of glycolysis?
Glucose + 2Pi + 2NAD + 2ADP > 2H2O + 2ATP + 2Pyruvate + 2NADH + 2H
What is the net reaction of glycolysis?
galactose > glucose 6-phosphate
fructose and mannose > fructose 6-phosphate
fructose > glyceraldehydes 3-phosphate
What are the three feeder pathways for glycolysis?
Pyruvate enters mitochondria and is converted to acetyl CoA. It goes through the citric acid cycle, electron transport chain, and oxidative phosphorylation. Lots of ATP is produced.
What is the fate of glucose under aerobic conditions?
In yeast, pyruvate is converted to ethanol (beer, wine)
In microorganisms and tumors, it is converted to lactic acid.
What is the fate of glucose under anaerobic conditions?
Tumors are characterized by their dependence on glycolysis for ATP (10x faster) and their tolerance to a low pH. They increase synthesis of glycolytic enzymes and transporters. HIF-1 induces peptide hormone VEGF which stimulates vessel growth. There is also a mutation of protein p53.
Describe the glycolysis of tumors
Muscle anaerobically breakdown glycogen for ATP and produce lactate during rapid contraction. Lactate is taken to the liver which uses ATP to convert lactate into glucose. Glucose then returns to the muscles to be stored as glycogen.
Describe the Cori cycle
since they lack organelles such as mitochondria, they convert pyruvate to lactic acid via fermentation.
Describe the fate of glucose in RBCs