Biochemistry- Carbohydrates Flashcards
What 2 monosaccharides make up lactose?
glucose and galactose
What 2 monosaccharides make up sucrose?
glucose and fructose
Which polysaccharide is comprised of glucose units linked by 1,4 alpha bonds?
amylose
What polysaccharide has glucose linked at 1,4 and 1,6 linkages?
glycogen
what polysaccharide has long chains of 1,4 linkages and every 25 molecules has a 1,6 branch?
Amylopectin
What polysaccharide has glucose molecules bound at beta 1,4 linkages?
cellulose (we can’t digest it! = fiber)
Which disaccharide has two glucose units?
Maltose
Sailvary amylase cleaves what type of bond?
alpha 1,4
maltase cleaves which linkage?
alpha 1,6
The enzymes maltase, sucrase, dextrine and lactase are found where?
brush border of mucosal cells
what is the rate limiting enzyme in the reaction of fructose to glucose?
fructokinase
What is the rate limiting enzyme in the reaction of galactose to glucose?
galactokinase
Dextrin is only released from the hydrolysis of which polysaccharide?
amylopectin
What hormone is released when glucose levels are high?
insulin
Which organ keeps a constant level of glucose in the blood by storing and producing it as needed?
the liver
Which organ does not require insulin to take up glucose?
the liver
Which hormone is released when glucose levels are down?
glucagon
Which of the catecholamines stimulates gluconeogenesis?
epinephrine
Glucokinase is only found in which organ?
the liver
in what part of the cell does glycolysis occur?
cytosol
What enzyme allows the liver to trap glucose in the form of glucose-6-phosphate?
glucokinase (hexokinase in other tissues)
What are 3 rate limiting enzymes of glycolysis?
gluco/hexokinase, phosphofructokinase, pyruvate kinase,
How many molecules of pyruvate do we get from one molecule of glucose?
2
What mineral is required for the phosphorylation reactions of glucokinase, hexokinase and phosphofructokinase?
Magnesium
What is the net ATP gained from aerobic glycolysis?
8 ATP (-2 ATP, +6 ATP from 2 NADH, +4ATP)
Which Krebs cycle intermediate inhibits action of phosphofructokinase and therefore inhibits glycolysis?
citrate
What is the aerobic fate of pyruvate?
Acetyl-CoA
Under anaerobic conditions pyruvate if reduced into:
Lactate
What enzyme complex converts pyruvate into Acetyl-CoA?
Pyruvate dehydrogenase complex
What vitamins are needed for the pyruvate dehydrogenase complex?
B1 (thiamin)
B2 (FAD)
B3 (NAD)
B5 Pantothenic acid
What mineral is required for the pyruvate dehydrogenase complex?
Magnesium
Pyruvate carboxylase converts pyruvate into what?
oxaloacetate
What cofactor is important in the carboxylation reaction of pyruvate to oxaloacetate?
Biotin
Why is the production of oxaloacetate from pyruvate important?
starts the Krebs cycle
What acts to promote pyruvate dehydrogenase and the subsequent formation of Acetyl-CoA?
The presence of pyruvate
What inhibits pyruvate dehydrogenase and promotes pyruvate carboxylase, thus shuttling pyruvate into oxaloacetate?
The presence of Acetyl-CoA
Where does the Krebs cycle take place?
In the mitochondria
Which metabolite of the Krebs cycle is used for fatty acid synthesis?
Citrate
Which 2 Krebs cycle metabolites are important for amino acid synthesis?
oxaloacetate and alpha keto-glutarate
Which krebs cycle metabolite is used in porphyrin/heme metabolism?
succinyl-CoA
Acetyl-CoA joins with what substance to form citrate?
oxaloacetate
What regulates the Kreb cycle?
ratio of ADP to ATP
What does high levels of ATP do to the Krebs cycle?
slows it down
What coenzymes are needed in the Krebs cycle?
B3- NAD
B2- FAD
B5 to make succinyl CoA
Name 4 uses for Acetyl CoA
ATP production, Fatty Acid synthesis, Ketone synthesis, Cholesterol formation
Which enzyme regulates the levels of Acetyl CoA?
Pyruvate dehydrogenase complex
What are 3 ways that the body can produce acetyl CoA?
- from pyruvate
- via beta oxidation of fatty acids
- alanine–>pyruvate, or from citrate
What are the 2 reducing equivalents?
NAD and FAD
What metabolite of the Krebs cycle is an important indicator of energy status of the cell?
Citrate
How is oxaloacetate transported out of the mitochondrion?
via converstion to malate (malate shuttle)
In what organs does the gluconeogenesis occur?
liver, sometime kidney
Which hormone, by its involvement with glucagon, inhibits glycolysis and promotes gluconeogenesis?
Epinephrine
What steroid hormone promotes the gluconeogenic pathway?
Cortisol
name 3 substrates for gluconeogenesis
- alanine
- glycerol
- lactate
What affect do fructose 1,6 diphosphate and 2,6 diphosphate have on gluconeogenesis?
inhibit it, by inhibiting fructose 1,6- diphosphotase
What are 2 products of the hexose monophosphate shunt?
NADPH, Ribose
What is the net output of the Krebs cycle?
3 NADH, 1 FADH, 1 GTP
What is the key rate limiting enzyme in glycogen synthesis?
glycogen synthase
What cytokine activates glycogen synthase?
insulin
What hormones inhibit glycogen synthase?
cortisol, glucagon
What substance in low quantities inhibits glycogen synthase?
cAMP
Which tissues have high amount of glycogen?
liver and skeletal muscle
Which metabolite in glycolysis is transformed into glycogen?
glucose-6-phosphate
What substance carries glucose molecules to the growing glycogen chain?
UDP
What is the rate-limiting enzyme in glycogenolysis?
phosphorylase
How is NADPH used in the body?
maintains Fe in RBCs
How many ATP molecules do you get from NADH?
3
How many ATP molecules do you get from 1 FADH?
2
Where does FADH enter the electron transport chain?
ubiquinone
What mineral is important in the electron transport chain?
Fe
What is the overall net energy output from 1 molecule of glucose?
8 ATP from glycolysis 2 NADH from pyruvate to acetyl CoA --> 6 ATP 6 NADH --> 18 ATP 2 FADH -->4 ATP 2 GTP--> 2 ATP Total 36-38 ATP
What is the final electron acceptor in the electron transport chain?
oxygen
The process of forming ATP from electrons is called what?
Transduction
