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173 Cards in this Set
- Front
- Back
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what are the seven intermediates of amino acid catabolism
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alpha ketoglutarate
oxaloacetate pyruvate fumarate succinyl CoA acetyl CoA acetoacetate |
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glucogenic amino acids
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amino acids whose catabolism yields pyruvate or one of the intermediates of the citric acid cycle. serve as substrates of gluconeogenesis
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ketogenic amino acids
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amino acids whose catabolism yields either acetoacetate or one of its precursors (acetyl CoA or acetoacetyl CoA)
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what are the only solely ketogenic amino acids
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leucine and lysine
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basic aims of metabolism
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formation of ATP
formation of reducing power formation of building blocks for biosynthesis |
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what are the control points of glycolysis
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hexokinase
phosphofructokinase (most important) pyruvate kinase |
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what inhibits PFK activity and therefore inhibits glycolysis
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high levels of ATP
decreased pH (acidic environment) high levels of citrate |
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what activates PFK
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fructose 2-6-bisphosphate
AMP and ADP |
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What does it mean to be ampipathic |
In reference to fatty acids. Containing a hydrophilic and and hydrophobic end |
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In unsaturated fatty acids what conformation are the double bonds |
Cis-formation |
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What is the first stage in triglyceride catabolism |
Hydrolysis |
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What is the fate of glycerol after it has been hydrolysed from triglycerides |
It is converted by intracellular enzymes to glycerol 3 phosphate. This then enters the glycolytic pathway for breakdown and energy use |
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In What form are 70% of the cholesterol in the lipoproteins of the plasma |
Cholesterol esters |
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What is the greatest source of cholesterol |
75% are endogenous. Made by the liver |
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Four main types of lipoproteins |
HDL- high protein concentration, small cholesterol and phospholipids IDL LDL VLDL- high triglyceride content |
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What is the primary function of lipoproteins |
Transport of lipid components in the blood |
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Where does VLDL mainly transfer triglycerides synthesized by the liver |
Adipose tissue ...and skeletal muscle |
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Which enzyme acts on VLDL and where is it found |
Lipoprotein lipase. The inner lining of the capillaries |
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How are triglycerides packaged for transport in the lymph |
Cholymicrons |
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Four main functions of bile salts |
Only legitimate pathway for cholesterol excretion Helps to keep cholesterol in solution Helps in digestion I.e. emulsification Facilitates in absorption of fat soluble vitamins ADEK |
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What is the bile salt precursor that is formed in the liver from cholesterol |
Cholic acid |
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Other functions of cholesterol |
Adrenocorticol hormones Testosterone Estrogen/progesterone Deposits in corneum of skin make it resistant to absorption of water soluble substances |
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Glutamate is metabolically converted to alpha-kg and NH4+ by a process described as |
Oxidative deamination |
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Which amino acid is an immediate precursor to urea |
Arginine |
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How does the urea cycle begin |
It begins with the coupling of free NH3 with HCO3 to form carbomyl phosphate |
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Dark urine upon standing in patients with alcaptonuria is due to: |
Accumulation of homogentisate due to absence of homogentisate oxidase. This intermediate is excreted in the urine is oxidized to a melanin like substance |
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What is PKU cause by |
An absence or deficiency of phenylalanine hydroxylase which converts phenylalanine to tyrosine |
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In maple syrup urine disease, the metabolic defect involves |
Blocked oxidative decarboxylation of alpha ketoacids because the branched chain dehydrogenase is missing or defective |
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What inhibits phosphofructokinase activity |
High levels of ATP Decreased pH levels (I.e. increased levels of lactic acid). High levels of citrate |
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Which enzyme converts pyruvate to acetyl CoA and where |
Pyruvate dehydrogenase in the matrix of the mitochondria. Irreversible reaction |
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What enzyme is the link between the TCA cycle and ATP formation in the electron transport chain |
Succinate dehydrogenase. It is embedded within the mitochondrial matrix and directly associated with the ETC |
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What hormones do alpha cells secrete |
Glucagon |
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Which hormones do beta cells of the pancreas secrete |
Insulin and amylin |
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What are the major effects of glucagon on glucose metabolism |
Increased glycogenolysis and gluconeogenesis |
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What effect does glucagon have on lipid metabolism |
It causes the activation of various hormones such as hormones sensitive lipases and adipose cell lipase which increase the amount of fatty acids available |
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How does insulin inhibiting carnitine acyl transferase affect lipid metabolism |
This keeps all of the fatty acid in the cytoplasm and outside the mitochondria thus decreasing beta oxidation |
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What enzyme does insulin activate in the capillary walls of the adipose tissue |
Lipoprotein lipase |
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What enzyme controls the rate limiting step of fatty acid biosynthesis |
Acetyl CoA carboxylase |
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Where does fatty acid synthesis occur |
It occurs in the cytoplasm |
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Where does beta oxidation occur |
In the mitochondrial matrix |
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Which tissues utilize ketone bodies |
Brain heart and kidney cortex |
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Where are ketone bodies formed |
The liver |
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What are the three principle ketone bodies |
D-beta- hydroxybutyric acid, acetone, acetoacetic acid |
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Percent body composition of water protein fat and minerals |
Water- 60% Protein-18% Fat-15% Minerals -7% |
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How does the urea cycle begin |
With the coupling of free NH3 with HCO3 to form carbomyl phosphate catalyzed by carbomylphosphate synthetase |
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Which reactions of the urea cycle occur in the mitochondrial matrix |
Formation of NH4+ by glutamate dehydrogenase Its incorporation into carbomyl phosphate as NH3 Synthesis of citrulline |
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Which reactions of the urea cycle occur in the cytoplasm |
Condensation of citrulline and arginine to form arginosuccinate Cleavage of arginosuccinate Hydrolysis of arginine to generate urea and ornithine |
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How does ammonia get from the peripheral tissues to organs that detoxify or excrete them |
Ammonia in the form of NH4 is combined to glutamate yielding glutamine (in peripheral tissues). In the liver glutamine is converted back to glutamate and ammonia. |
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How is ammonia toxic to human brain cells |
It can easily enter the mitochondria which leads to the formation of glutamate and alpha-kg. Leads to depletion of akg from Krebs cycle thus lowering rate of glucose oxidation and depriving the brain of glucose |
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Which animals are uricotelic |
Birds, lizards, and snakes |
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In which two ways is nitrogen transferred from the muscle to the liver |
Nitrogen is transaminated to glutamate which donates the amino group to pyruvate to form alanine. Liver takes up alanine and converts it back to transaminstion. Pyruvate goes thru gluconeogenesis and amino group goes to the cycle 2) glutamine |
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Which drug can be used to treat hyperuricimia |
Allopurinol which is a xanthine oxidase derivative |
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How is PKU caused |
An absence or deficiency of phenylalanine hydroxylase leading to an accummulation of phenylalanine in the blood |
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Which metabolite of the phenylalanine minor shunt pathway leads to mental retardation |
Phenylpyruvic acid |
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What are the clinical features of PKU |
Mental retardation Light pigmentation Impaired gait, stance, posture Eczema Epilepsy |
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What was the first identified inborn error of metabolism |
Alcaptonuria. Metabolic disorder caused by the absence of homogentisate oxidase |
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How is branched chain ketonuria or maple syrup disease caused |
Missing or defective alpha-ketoacid dehydrogenase leading to increased levels of alpha- ketoacids from valine, isoleucine, and leucine in the blood and urine |
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What kind of reaction does alpha ketoacid dehydrogenase catalyzd |
Oxidative decarboxylation |
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What is albinism caused by |
A defect in tyrosine metabolism resulting in a deficiency of melanin production |
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How does glucose absorption into liver cell membranes differ from that of the GIT and renal tubules |
Its absorbed against its concentration gradient by active sodium glucose co transport in the GIT and tubules |
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The phosphorylation of glucose is catalyzed by which enzymes |
Glucokinase in the liver and hexokinase in other cells |
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Which enzyme is able to reverse the irreversible phosphorylation of glucose and in which cells is it found |
Glucose phosphotase. Liver cells. Renal tubular epithelial cells and intestinal epithelial cells |
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Which irreversible step serves as the rate limiting step of glycolysis |
Conversion if fructose 6 phosphate to fructose 1,6 bisphosphate by phosphofructose kinase |
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What inhibits PFK |
ATP and a decrease in pH |
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What enzyme catalyzes the substrate level phosphorylation of 1,3 BPG to 2 phosphoglycerate |
Glyceraldehyde 3 phosphate dehydrogenase |
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How is NAD+ regenerated |
Through metabolism of pyruvate |
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What acts as a cofactor for pyruvate decarboxylase |
Thiamine pyrophosphate which is derived from Vit B1 |
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Where does homolactic fermentation take place |
Occurs in cells lacking oxygen and mitochondria or in muscle cells during intense activity |
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What enzyme catalyzes the reduction of pyruvate to lactate |
Lactate dehydrogenase |
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What kind of reaction is the conversion of pyruvate to acetyl CoA and where does it occur |
Oxidative decarboxylation. Mitochondria |
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What is glucokinase used for in the liver |
It provides G6P for glycogen and the formation of fatty acids. |
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Why is glucokinase's low affinity for glucose metabolically relevant |
It ensures that the brain and muscles get first supply when glucose is limited and ensures the glucose is not wasted when it is abundant |
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What inhibits hexokinase |
Rising levels of G6P |
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What are the two major outputs of the Pentose phosphate pathway in animal cells |
Ribose 5-phosphate for nucleic acid synthesis NADPH for biosynthetic reduction or plasma membrane reduction and maintenance |
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What substrate is needed to keep the membrane in reduced form that is recycled by NADPH |
Glutathione |
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Transketolase reaction |
Transfer 2-carbon keto groups from a variety of ketose sugars to an aldehyde |
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How many molecules of NADPH are regenerated through oxidative generation of the PPP |
Two |
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What enzyme catalyzes the dehydrogenation of G6P |
Glucose 6 phosphate dehydrogenase |
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Why are transketolase and transaldolase reactions linked to PPP |
Some cells need NADPH more than they need ribose 5 phosphate for nucleotide synthesis. Therefore these enzymes are used to produce glyceraldehyde 3 phosphate and fructose 6-phosphate from R5P |
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What molecule transiently holds on to the keto group before transfer |
Thiamin pyrophosphate cofactor |
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What reaction does the transketolase catalyze in PPP |
R5P + xylulose 5 phosphate to form glyceraldehyde 3 phosphate |
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Transaldolase reaction |
Transfer 3 carbon dihydroxyacetone unit from a ketose donor to an aldose acceptor |
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What inhibits dehydrogenation of G6P |
Low levels of NADP+ because it is needed as an electron acceptor |
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Which hormones stimulate glycogen degradation in the liver |
Glucagon and adrenaline |
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Which hormone stimulates glycogen degradation in striated muscle |
Adrenaline |
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What stimulates glycogen degradation in skeletal muscle |
Depolarisation |
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What stimulates glycogen synthesis in the liver |
Glucose |
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What stimulates glycogen synthesis in skeletal muscle |
Insulin |
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What is the primary enzyme involved in the control of glycogen metabolism |
Glycogen phosphorylase |
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Which hormones stimulate the breakdown of glycogen |
Glucagon and epinephrine |
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What enzyme inactivates glycogen phosphorylase |
Protein phosphatase 1 |
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Which steps in gluconeogenesis bypass the irreversible steps of glycolysis |
1) Formation of phosphoenolpyruvate by way of oxaloacetate from pyruvate 2) formation of fructose6 phosphate from fructose 1,6 bisphosphate by hydrolysis of the ester 3) formation of glucose from glucose 6-phosphate catalyzed by its phosphatase |
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Which reaction of gluconeogenesis takes place in the mitochondrial matrix |
Reaction catalyzed by pyruvate carboxylase |
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What kind of reaction is the conversion of alanine to pyruvate |
Deamination |
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What are the two ways for mitochondrial oxaloacetate to enter the cytosol to be available for gluconeogenesis |
1) conversion to PEP. Occurs in matrix by action of PEP carboxykinase 2) reduction to malate. Malate enters the cytosol and is converted to oxaloacetate using cytosolic PEP carboxykinase |
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How does glucagon and insulin affect PEPCK activity |
Glucagon increases its transcription. Insulin decreases its transcription |
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What kind of reaction is defective in maple syrup disease |
Oxidative decarboxylation of alpha ketoacids |
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What is an enzyme that is active in both glycolysis and gluconeogenesis |
3-phosphoglycerate kinase |
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Which are reducing sugars |
Sugars with a C1-4 and C1-6 glycosidic linkage. Glucose Fructose Glyceraldehyde Lactose Arabinose Maltose Isomaltose |
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What are non reducing sugars |
Sugars with C1-1 and C1-2 glycosidic linkage. Trehalose Sucrose Glycogen Insulin |
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Which enzymes hydrolyze lactose to galactose and glucose |
Lactase in humans and beta galactosidase in bacteria |
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Describe the structure of maltose |
Produced from 2 molecules of glucose joined by an alpha 1,4- glycosidic linkage |
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Describe the structure of cellobiose |
Identical to maltose except it is formed by beta 1-4 glycosidic linkage |
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What are some causes of low biopsy enzyme activity |
Subnormal expression of the enzyme gene Normal expression of a mutant enzyme gene Presence of abnormal intracellular inhibitor Lack of normal intracellular inhibitor |
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The C1 aldehyde in the open chain form of glucose reacts with the C5 hydroxylase group to form what |
An intramolecular hemiacetal |
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The C2 keto group in the open chain form of fructose can react with the C5 hydroxyl group to form what |
An intramolecular hemiketal |
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Specific rotation |
The observed rotation of light of wavelength 579 nm passing through 10cm of a 1g/ml solution |
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What conformation is the most favored in solution and why |
The chair form of beta-D-glucopyranose is the predominant one because all axial positions are occupied by hydrogen bonds |
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O-glycosidic bond |
Bond formed between the anomeric carbon atom of a sugar and the hydroxyl oxygen atom of an alcohol |
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What conformation are all N-glycosidic bonds always found in nature |
Beta position |
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Phosphorylation makes sugars anionic. Why is this important |
It prevents sugars from spontaneously exiting the lipid bilayer membranes |
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Where does chymotripsin cleave the polypeptide chain |
On the carboxyl side of aromatic amino acids |
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What are the nine essential amino acids |
Valine Leucine Isoleucine Methionine Phenylalanine Tryptophan Threonine Lysine Histidine |
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Which amino acid is not optically active |
Glycine |
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Structure of cellobiose |
Two molecules of glucose formed by beta 1,4 glycosidic linkage |
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Structure of cellulose |
An anhydride of glucose linked by beta 1,4 linkages |
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Characteristics of reducing sugars |
C1-4 and C1-6 glycosidic linkages Glycosylaldose or glycosylketose Hemiacetal or hemiketal Exhibit mutarotation |
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Which sugars are reducing sugars |
Glucose Fructose Glyceraldehyde Lactose Arabinose Maltose Isomaltose |
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Characteristic of non reducing sugars |
C1-1 and C1-2 glycosidic linkage Glycosylglycosides. No free aldehyde or ketone group Do not exhibit mutarotation |
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Non reducing sugars |
Trehalose Sucrose Glycogen Insulin |
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Which compounds contain glucoronic acid |
Hyaluronic acid Chondroitin Dermatan sulfate Heparin |
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The C1 aldehyde in the open chain form of glucose reacts with the C5 hydroxyl group to form what |
An intramolecular hemiacetal |
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What is a enzymatic biopsy used to determine mainly |
Inborn error |
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What are some causes of low biopsy enzyme activity |
Subnormal expression of the enzyme gene Normal expression of mutant enzyme gene Presence of abnormal intracellular inhibitor Lack of a normal intracellular inhibitor |
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Substrate induced cleft closing is a general feature of kinases |
Fact |
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Which kinds of reactions are typically catalyzed by proton transfer |
Esterification and adol reactions |
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Affect of competitive inhibitor on Km and Vmax |
Increases the Km but Vmax remains the same |
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Affect of non competitive inhibition on value of Vmax and Km |
Decreases Vmax but Km remains unchanged |
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An allosteric enzyme is normally the committing enzyme for a metabolic pathway |
Fact |
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What does aspartate transcarbomylase (ATCase) catalyze |
The first step in the biosynthesis of pyrimidines. A condensation reaction of aspartate and carbomyl phosphate. Committed step in formation of pyrimidine nucleotidw |
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What inhibits ATCase activity |
CTP |
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Which amino acids have basic side chains |
Arginine, lysine, and histidine |
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Which amino acids have acidic side chains |
Aspartate and glutamate |
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At what pH are amino acids neutrally charged |
At their isoelectric point |
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Where does the majority of fat digestion occur |
Small intestine |
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What is the first step of fat digestion |
Physical breakdown (emulsification) of fat globules into small sizes |
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List the essential amino acids that are glucogenic |
Histidime Methionine Threonine Valine |
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List the essential amino acids that are glucogenic and ketogenic |
Isoleucine Phenylalanine Tryptophan |
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List the essential amino acids that are ketogenic |
Leucine Lysine |
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Which kind of reactions convert glutamate to alpha kg |
Transamination or oxidative deamination by glutamate dehydrogenase |
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What is the cofactor for amino acid transamination |
The active form of Vitamin B6 which is pyridoxal phosphate |
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Which amino acids can be catabolised to pyruvate |
Alanine Cysteine Glycine Serine Threonine Tryptophan |
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What process is defective in Maple Syrup Urine Disease and why |
Oxidative decarboxylation of alpha ketoacids because the branched chain dehydrogenase is missing or defective |
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What is the inherited autosomal recessive trait that leads to an increased osmotic pressure in the lumen of the intestines causing abdominal distention, cramps, pain, nausea and watery diarrhea |
Lactose intolerance because of a deficiency in lactase |
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What is a reducing sugar |
They have free aldehyde or ketone groups that forms an aldehyde or ketone in solution |
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Which sugars are reducing sugars |
Glucose Fructose Glyceraldehyde Lactose Arabinose Maltose Isomaltose |
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Definition of a non reducing sugar |
They do not have a free aldehyde or ketone group because they reduce each other there is none available for further reduction |
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What is the storage sugar of plants |
Sucrose |
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How do plants make sucrose |
By the elimination of water from glycosidic hydroxyl groups or alpha D glucose and beta D fructose |
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Milk sugar |
Lactose |
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Structure of lactose |
Galactose and glucose joined by a beta 1,4 glycosidic linkage |
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Structure of maltose |
Two molecules of glucose by an alpha 1,4- glycosidic linkage |
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Structure of cellobiose |
Identical to maltose (two glucose molecules ) except beta 1-4 glycosidic linkage |
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Structure of isomaltose |
Similar to maltose except it has an alpha 1-6 linkage |
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Function of polysaccharides |
Energy storage Maintaining the structural integrity of an organism |
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How is starch formed |
Formed by the condensation of glucose residues |
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What is the composition of starch |
15-20% amylose and 80-85% amylopectin |
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What is amylose |
An anhydride of glucose that results from 1-4 glucoside linkage |
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Structure of dextran |
Glucose residues joined almost exclusively by alpha 1-6 glycosidic linkages |
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How is dextran synthesized |
Synthesized from sucrose by lactic acid bacteria |
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Structure of insulin |
A polyfructose |
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Structure of pectin |
A soluble polymer of D galacturonic acid |
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Structure of chitin |
Linear polymer of N-acetyl-D-glucosamine units joined by beta 1,4 glycosidic linkages |
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What is one of the simplest heteropolysaccharide |
Antigens of pneumococcus type III |
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Structure of antigen of pneumococcus type III |
Glucose and glucoronic acid |
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Structure of hyaluronic acid |
D glucoronic acid and N acetyl glucosamine (NAG) linked with alternating beta 1-4 and 1-4 glycosidicbonds |
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Structure of chondroitin |
A sulfated glycosaminoglycan made up of alternating sugars 1,3 Nacetylglucosamine and glucaronic acid joined by 1,4 linkages |
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What stimulated glycogen degradation in the liver |
Glucagon and adrenaline |
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Product of the intestinal digestion of triglyceride include |
An oil phase consisting of triglyceride and diglyceride and a micellar phase of monoglyceride, bile salt and free acid |
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Glycoholic and taurocholic acids are major conjugated bile acids |
True |
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Some of the conjugated bile acids are returned to the liver from intestine via the enterohepatic circulation |
True |
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The major component of bile besides the conjugated bile acids are phosphatidyl choline and cholesterol |
True |
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What interferes with collagen crosslinking my effecting lysyl oxidase |
Copper deficiency Nitrile inhibitors Lathyrus odoratus |
