Lecture 14 Flashcards
Define standard free energy and relate it to exergonic and endergonic reactions
Difference in free energy when 1 mole of each reactant is converted to 1 mole of each product at 1 atm pressure at 25 degrees C; negative in an exergonic reaction and positive in an endergonic reaction
Relate free energy to ATP breakdown
Highly negative (exergonic)
How does galactose and glucose enter glycolysis?
Galactose and glucose can be converted through a series of reactions into fructose-6-phosphate and then enter glycolysis
Describe the uptake of glucose
Occurs via active sodium-glucose co-transport in GI tract and renal tubules; occurs via facilitated transport (higher to lower concentrations) in most tissues; presence of insulin increases glucose transport x10, phosphorylation of glucose prevents diffusion out of the cell, and phosphorylation can be reversed in liver, renal, and intestinal cells
What are the end products of glycolysis?
2 molecules of pyruvic acid, 4 molecules of hydrogen ions, and 2 molecules of ATP
What are the end products of the conversion of pyruvic acid to acetyl-CoA?
2 molecules of acetyl-CoA, 4 hydrogen ions, and 2 molecules of carbon dioxide
What is the fate of pyruvic acid when oxygen is not present?
Converted into lactic acid
What are the end products of the citric acid cycle?
16 hydrogen ions, 2 molecules of ATP, and 4 molecules of carbon dioxide
Define oxidative phosphorylation and state where it occurs
Occurs on mitochondrial cristae;
Define oxidative phosphorylation and state where it occurs
Occurs on mitochondrial cristae; think electron transport chain; per glucose molecule, we get 2 ATPs from glycolysis, 2 ATPs from the TCA cycle, and 34 ATPs from oxidative phosphorylation
What is the fate of the hydrogen atoms and the electrons generated during glycolysis and the citric acid cycle? Name and compare the hydrogen ion carriers
Hydrogens are removed in pairs with one becoming an ion and the other pairing with NAD+ to become NADH
List, in sequence, the components of the electron transport chain
Flavoprotein, several iron sulfide proteis, ubiquinone (Q), cytochrome A3 (cytochrome oxidase)
Describe the pentose phosphate pathway and explain what it is primarily used for
Cyclical pathway in which one molecule of glucose is metabolized for each revolution of the cycle; mostly used for the synthesis of fats and other substances
Describe the transport mechanism for hydrogen ions in the pentose phosphate pathway
Instead of using NAD+, hydrogens in this pathway are bound to NADP+, which can be used in the synthesis of fats from carbohydrates and NADPH participates in the conversion of acetyl-CoA into fatty acid chains
Describe how trigylcerides are synthesized from glucose
Can be synthesized via alpha-glycerophosphate or made into fatty acids and then into triglycerides
Explain how trigylcerides are absorbed from the intestinal lumen
Most triglycerides are digested into monoglycerides and fatty acids; intestinal epithelial cells resynthesize these into triglycerides that enter the lymph as chylomicrons
Define chylomicrons and explain how they are transported and removed from the blood. What is the role of lipoprotein lipase?
Transported to the venous system via the thoracic duct and removed from the blood by various tissues (adipose, skeletal, heart); lipoprotein lipase is synthesized by these tissues, is transported to surface of capillary epithelial cells, and hydrolzes chylomicron trigylcerides, releasing fatty acids and glycerol
Compare fat to carbohydrates as an energy source and explain under what conditions fat is used for energy
All normal energy requirements of the body can be provided by the oxidation of fatty acids without using carbohydrates or proteins as an energy source; starvation and diabetes mellitus increase the utilization of fat for energy
Define lipoprotein and compare the various types of lipoproteins
Lipoproteins transport lipids in the blood; chylomicrons are synthesized by intestinal cells and VLDLs (very low density), LDLs (low density), and HDLs (high density) are synthesized by the liver
VLDLs: high concentrations of triglycerides and moderate amounts of cholesterol and phospholipids; transport lipids mainly from liver to adipose tissue
LDLs: high concentration of cholesterol and moderate concentration of phospholipids
HDLs: high concentration of proteins and low concentration of cholesterol and fatty acids
How are triglycerides used as an energy source?
Hydrolyzed into fatty acids and glycerol, which are transported in blood to tissues; almost all cells except brain cells and rbcs use fatty acids for energy
Describe the formation of acetoacetic acid
Fatty acids degraded in the liver release many acetyl-CoA’s not used for metabolism; 2 acetyl-CoA’s condense to form acetoacetic acid; some of this is converted to beta-hydroxybutyric acid or acetone
Define ketone bodies and give examples. What is ketosis?
Ketone bodies are molecules that contain ketone groups and include beta-hydroxybutyric acid, acetoacetic acid, and acetone
Ketosis is the concentrations of ketone bodies increasing above normal in the blood
List and describe the sequence of steps in the formation of an atherosclerotic plaque
- Damage to vascular epithelium (increases the expression of adhesion molecules, decreases release of NO and other substances that prevent adhesion of macromolecules and cells)
- Circulating monocytes and LDLs accumulate at injury site
- Monocytes ( cross endothelium, enter intima, become macrophages)
- Macrophages ( ingest lipoproteins, become foam cells, form visible fatty streaks)
- Fatty streaks ( grow larger, coalesce)
- Surrounding fibrous and smooth muscle tissues (proliferate, form large plaques)
