Biochem: Carbohydrates Flashcards
_________ are absorbed by enterocytes in the small intestine.
Monosaccharides
What are the three major disaccharides and what are their components?
MLS
Maltose = glucose + glucose Lactose = glucose + galactose Sucrose = glucose + fructose
T/F: Glycosaminogylcans (GAGs) are repeating disaccharides.
True
High viscosity and low compressibility
T/F: GAGs are negatively charged and attract water.
True
What is the most abundant GAG?
Chondroitin sulfate
What are the only two GAGs that do not end in “sulfate”?
Heparin and hyaluronic acid
Why do PGs attract water?
Large number of alcohol groups
The central protein in a PG contains which two amino acids?
Serine and threonine
Cariogenic bacteria synthesize _______ and ________ from their metabolism of dietary _________.
glucans (dextrans); fructans (levans); sucrose
Strep Mutans contains which enzyme that hydrolyzes sucrose to form dextrans (glucans)?
glucosyl transferase
T/F: Glycogen is stored in the liver.
True
What is the major buffer found in saliva?
Bicarbonate
What is the major antibody found in saliva?
IgA
Which gland produces the majority of the saliva?
Submandibular
During glycolysis glucose gets converted to __________.
pyruvate
When oxygen is present, pyruvate will be converted to _________. Without oxygen, pyruvate will be converted to ________.
Acetyl-CoA (Kreb’s Cycle); Lactic acid
What three major coenzymes make up the pyruvate dehydrogenase complex?
- Coenzyme A
- NAD
- Thiamine
What is the function of the pyruvate dehydrogenase complex?
To get pyruvate into the mitochondria
What is the first step of the citric acid cycle?
Citrate synthase converts Acetyl-CoA, Oxaloacetate, and water into citrate
What happens to convert pyruvate to Acetyl-CoA?
Oxidation by pyruvate dehydrogenase
Glycolysis -> Kreb’s Cycle
What happens to convert pyruvate to lactic acid?
Reduction by lactate dehydrogenase
Anaerobic
What happens to convert pyruvate to oxaloacetate?
Carboxylation by pyruvate carboxylase
Gluconeogenesis and replenish TCA cycle
What happens to convert pyruvate to alanine?
Transamination by alanine aminotransferase
Amino acid synthesis
If Acetyl-CoA is not acted on by citrate synthase, what are the other possible routes?
Acetyl-CoA is either converted to Malonyl-CoA or HMG-CoA
What enzyme converts Acetyl-CoA to Malonyl-CoA?
Acetyl-CoA carboxylase
Occurs in cytosol in liver; rate limiting step in fatty acid synthesis
What are the two routes for HMG-CoA?
- Cholesterol synthesis via HMG-CoA reductase
2. Ketone body synthesis via HMG-CoA lyase
What are the three major components of gluconeogenesis?
LAG
Lactate, amino acids, glycerol
What is the net yield of ATP through glycolysis (cytosol)?
uses two, makes four
Net = +2
What is the net yield of ATP in the TCA cycle (mitochondrial matrix)?
Net = +2
What is the net yield of ATP in the ETC (inner mitochondrial membrane)?
+34
What enzyme allows glucose to be brought from the blood into tissue?
Hexokinase/glucokinase uses an ATP to convert glucose (blood) to glucose-6-phosphate (tissues)
What is the purpose of the pentose phosphate shunt?
Produce ribose (DNA synthesis) and NADPH (fatty acid and steroid synthesis)
Which part of the nervous system would stimulate glucagon release?
Sympathetics
Would result in gluconeogenesis to put glucose into the blood stream
Which part of the nervous system would stimulate insulin release?
Parasympathetic
T/F: Acetyl-CoA is used in gluconeogenesis to make new glucose.
False
LAG
Lactate, amino acids, glycerol
T/F: Insulin will stimulate glycogenolysis.
False
Insulin -> glycogenesis (store glucose)
Glucagon -> glycogenolysis (lyse glycogen to release glucose)
What is the goal of the cori cycle?
Lactate from muscles is brought to liver to convert to glucose
T/F: Glycogen phosphorylase converts glycogen to glucose-1-phosphate.
True
Stimulated by glucagon, epinephrine
Describe how glucose is converted into glycogen?
glucose -> glucose-6-phosphate -> glucose-1-phosphate -> UDP-glucose
Glycogen synthase attaches UDP-glucose to the nonreducing end of glycogen
T/F: Ketone bodies can be a source of energy for the brain when in fasting.
True
