Term
| Explain the absorption of monosaccharides |
|
Definition
| Absorption of glucose and galactose by mucosal cells in the small intestine is an energy requiring process which needs constant uptake of Na+ ions. Fructose is absorbed by GLUT5 transporters. All monosaccharides are transported from mucosal cells to portal vein by GLUT2. |
|
|
Term
| What are the two principal sites of carb digestion? |
|
Definition
| Mouth and intenstinal lumen |
|
|
Term
| What enzymes are responsible for carbohydrate digestion and where are they located? |
|
Definition
| Endoglycosidases, disaccharidases. The are present in the saliva, pancreatic juices and mucosal lining of the small intestine. |
|
|
Term
| What reaction breaks down carbs? How? |
|
Definition
| Hydrolysis breaks down carbs by adding a water molecule to break molecule. This is a huge reason why water is so important in the body. |
|
|
Term
| What reaction builds carbs? How? |
|
Definition
| Condensation reaction removes a water to join two molecules. |
|
|
Term
|
Definition
homopolysaccharide made of alpha-D-glucose
storage form of glucose in the body |
|
|
Term
| What are the types of starch and where are they found? |
|
Definition
Amylose - linear chains of glucose
Amylopectin - branched chains of glucose
Found in grains, legumes, tubers
Most are easily digested in GI tract but some are resistant (legumes) |
|
|
Term
|
Definition
| non-digestible carbohydrates + lignin |
|
|
Term
|
Definition
| non-digestible carbs, resistant starch, non-starch polysaccharides (cellulose, pectins, chitin) |
|
|
Term
| How is glycogen distributed through the body? |
|
Definition
Liver glycogen is stored and released to body in between meals through the portal vein. Can store enough for the whole body for about 10-18 hours.
Muscle glycogen cannot leave the liver because it cannot be dephosphorylated (no glucose-6-phosphatase). Its released to muscle cells during mucle contraction and exercise. |
|
|
Term
| What are the enzymes in glycogenolysis and what do they do? |
|
Definition
1) glycogen phosphorylase: cuts 1-4 glycosidic bonds until there are four glucose residues from a branching point
2) transferase: cuts three glucose segments and transfers them to a linear chain of glucose
3)debranching enzyme: cuts off glucose residues at the 1-6 bond
glycogen phosphorylase is the regulatory enzyme of glycogenolysis |
|
|
Term
| What are the inhibitors of glycogenolysis? |
|
Definition
Glucose and glucose-6-phosphorylase inhibit glycogen phosphorylase because they signal there is available glucose.
AMP and Ca+ activate glycogenolysis by activating glycogen phosphorylse. Ca+ binds to calmodulin which is a subunit of phosphorylase kinase which activates glycogen phosphorylase. |
|
|
Term
| What is glucogenesis? How does it work? |
|
Definition
| Glycogenesis is the synthesis of glycogen from glucose. Glucose is fused with UTP to make UDP glucose which is then synthesized to glycogen by the enzyme glycogen synthase. Branching enzyme branches the molecule which makes it very compact and able to fit in the body. |
|
|
Term
| What are the inhibitors and activators of glucogenesis? |
|
Definition
Glucogenesis is activated by glucose-6-phosphatase which activates glycogen synthase.
I believe insulin is also an activator because insulin would signal that there is glucose in the blood that needs to be used. |
|
|
Term
| What occurs in the first step of glycolysis? Include the function of the enzymes |
|
Definition
The first step of glycolysis requires energy. Glucose is the substrate and glyceraldehyde-3-phosphate is the product. Hexokinase and glucokinase phosphrylate glucose to glucose-6-phosphate. In the rate-limiting step, PFK phosphorylates fructose-6-phosphate to fructose 1-6 bisphosphate.
PFK-1 is inhibited by ATP and citrate.
PFK-1 is activated by AMP and inorganic phosphate. |
|
|
Term
| What are inhibitors and activators of glycolysis? |
|
Definition
Insulin activates glycolysis enzymes
Glucagon inhibits glycolysis enzymes
Insulin and glucagon regulate activity of pyruvate kinase though cAMP dependent PKA |
|
|
Term
| What are the products of glycolysis? |
|
Definition
| 2 ATP, 2 NADH, 2 pyruvate |
|
|
Term
| Explain the second phase of glycolysis. |
|
Definition
In the energy-producing step glycerhyde-3-phosphate is substrate and pyruvate is the product. Phosphoglycerate kinase produces 3-phosphoglycerate and ATP from ADP and 1,3-bisphosphateglycerate.
Pyruvate kinase forms pyruvate (and ATP) from phosphorenolpyruvate. Pyruvate is then either used to make lactate or used in the Krebs cycle. |
|
|
Term
| How is pyruvate converted to acetyl-CoA |
|
Definition
Pyruvate is converted to acetyl-CoA by the enzyme complex pyruvate dehdrogenase complex. This is five co-enzymes: CoA, NAD+, FADH, lipoic acid and thiamine pyrophosphate.
PDH is inhibited by acetyl CoA and NADH
PDH is activated by calcium during muscle contraction |
|
|
Term
| What are the regulatory enzymes of the Krebs cycle and what do they do? |
|
Definition
Citrase: condensation of acetyl CoA and oxaloacetate to form citrate
Isocitrate dehydrogenase: Rate limiting step. catalyzes oxidative decarboxylation of isocitrate yield the first NADH molecule and first release of CO2.
alpha-ketogluterate dehydrogenase complex: conversion of α-ketogluatartae to succinyl cOA |
|
|
Term
| What is oxidative phosphorylation? What's its role in the ETC? |
|
Definition
| Oxidative phosphorylation is the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers. Forms ETC in inner mitochondrial membrane and is major source of energy. |
|
|
Term
| How is cystolstic NADH (from Krebs) transported to mitcohondrial matrix for ETC? |
|
Definition
Glycerophosphate shuttle -> 2 ATP
Malate-asparate shuttle --> 3 atp |
|
|
Term
| How is ATP transported from ETC in the inner mitochondrial matrix to the cytoplasm? |
|
Definition
| Its transported by adenine nucelotide carrier |
|
|
Term
| How many ATP do NADH and FADH2 provide? |
|
Definition
Oxidation of NADH provides 3 ATP because it enters ETC at first proton pump
Oxidation of FADH2 provides 2ATP cuz it enters at second proton pump |
|
|
Term
| Where do the reduced coenzymes NADH and FADH2 come from for the ETC? |
|
Definition
The majority come from Krebs cycle which is in the mitochondrial matrix next to the ETC.
Some comes from glycolysis - these need shuttles to be transported from the cytoplasm to the mitochondrial matrix.
GLycerophosphate shuttle transfers FADH2
Malate-asparate transfers NADH |
|
|
Term
| What are the 3 types of inhibitors of the ETC? |
|
Definition
Site-specifc inhibitors: barbiturates, carbon monoxide
Uncouplers: increase the permeability of the mitochondrial membrane - aspirin
ATP synthase inhibitors: oligomycin |
|
|
Term
|
Definition
Uncoupling protein 1.
Proton pump is uncoupled from ATP synthase
fatty acids are oxidized to produce FADH and NADH
energy released as heat
Its a component of brown adipose tissue and is responsible for nonshivering thermogenesis |
|
|
Term
| What happens in the first phase of glycolysis? |
|
Definition
| In the energy producing phase, glucose/galactose/fructose are the substrates and G3P is the product. Hexokinase, glucokinase or fructose kinase phosphorylate the monosaccharide to glucose-6-phosphate. Galactose needs UDP glucose to be utilized in glyolysis. PFK-1 phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate so that it can be utilized later in the pathway. PFK-1 is inhibited by high levels of ATP and citrate. It is activated by AMP and inorganic phosphate. 2ATP are required to begin the process |
|
|
Term
| What happens during the second phase of glycolysis? |
|
Definition
| G3P is the substrate. Phosphoglycerate kinase, phosphorylates 1,3-bisphosphoglycerate to 3-phosphoglycerate. Pyruvate kinase produces pyruvate and lactase converts pyruvate to lactose in anaerobic conditions |
|
|
Term
| How is glucose transported into cells? |
|
Definition
| Glucose is transported into cells via GLUT 1-12 transporters. GLUT 4 is insulin dependent. GLUT2 can transport all monosaccharides out of the cell. GLUT5 transports fructose. |
|
|
Term
| What does pyruvate kinase do and what are its activators/inhibitors? |
|
Definition
| Pyruvate convers 2-phosphoenol pyruvate to pyruvate for use in the Krebs cycle. Its inhibited by ATP in the body. Its activated by fructose 1,6-bisphosphate (from first step of glycolysis) |
|
|
Term
| What does PFK-1 do? How is it regulated? |
|
Definition
PFK-1 phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate.
PFK-1 is activated by AMP and Pi. It is inhibited by high levels of ATP and citrate |
|
|
Term
| What is fructose 2-6-bisphosphates role in glycolysis? |
|
Definition
| When insulin is high it causes degratation of cAMP which inhibits PKA which activates PFK-2 which activates formation of fructose2,6-bisphosphate which activates PFK1 which increases glycolysis |
|
|
Term
| What is fructose-2-6-bisphosphates role in glucoeneogenesis? |
|
Definition
| Glucagon activates cAMP which activates PKA. PKA suppresses pyruvate kinase which prevents pyruvate from being produced so gluconeogenesis is utilized instead of glycolysis. |
|
|
Term
| What is the role of RBCs in glucose metabolism? |
|
Definition
| RBCs don't have mitochondria so they have no oxygen. GLUT1 transports glucose into the cell. Lactate is produced and released to the liver to be utilized as pyruvate. |
|
|
