GI System Biochem 1 Flashcards
What 2 monosaccharides make up lactose?
Galactose and glucose
What 2 monosaccharides make up sucrose?
Glucose and fructose
Which polysaccharide is composed of glucose units linked by alpha-1,4 linkages?
Amylose
What polysaccharide has glucose linked by alpha-1,4 and alpha-1,6 linkages?
Glycogen
What polysaccharide has long chains of alpha-1,4 linkages and every 25 molecules has an alpha-1,6 branch?
Amylopectin
What polysaccharide has glucose molecules bound at beta 1,4 linkages?
Cellulose
Which disaccharide has 2 glucose units?
Maltose
Salivary and pancreatic amylase breaks down what type of linkages?
Alpha-1,4
Maltase cleaves which linkage?
Alpha-1,4
Isomaltase cleaves which linkage?
Alpha-1,6
The enzymes maltase, sucrase, dextrinase and lactase are found where?
In the brush borders of the 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. These processes are called gluconeogenesis or glycogenesis.
Which tissues do not require insulin to take up glucose?
The liver, brain, RBC. Only skeletal muscle and adipose require insulin to uptake glucose. Brain and RBCs require a constant supply of sufficient oxygen and thus can’t afford to rely on a fluctuating insulin status. Liver is involved with the constant homeostasis of glucose and also thus should not be dependent on insulin status.
Which hormones are released when glucose levels are down?
Glucagon, epinephrine, cortisol. These hormones all mitigate hypoglycemia by influencing insulin.
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 of the cytoplasm.
What enzyme allows the liver to trap glucose in the form of glucose-6-phosphate?
Glucokinase
What are the 3 rate-limiting enzymes of glycolysis?
Hexokinase/glucokinase
Phosphofructokinase
Pyruvate kinase
How many molecules of pyruvate do we get from one molecule of glucose?
Two
What mineral is required for the phosphorylation reactions of glucokinase and phosphofructokinase?
Magnesium
What is the net harvest from aerobic glycolysis?
8 atp (2 atp, +6 atp from 2 nadh, +4 atp)
Which Krebs cycle intermediate inhibits action of phosphofructokinase and therefore inhibits glycolysis?
Citrate
What is the net harvest of anaerobic glycolysis?
2 atp (nadh still gets produced but under anaerobic conditions does not get oxidized)
What is the aerobic fate of pyruvate?
Acetyl-CoA
Under anaerobic conditions pyruvate is reduced to what?
Lactate
What enzyme complex converts pyruvate into Acetyl-CoA?
Pyruvate dehydrogenase complex. This enzyme requires Mg.
What vitamins are needed for the pyruvate dehydrogenase complex?
Vitamin B1 or thiamin
Vitamin B2 in the form of fad
Vitamin B3 in the form of nad
Vitamin B5 in the form of CoA
What mineral is required for the pyruvate dehydrogenase complex?
Magnesium
Pyruvate carboxylase converts pyruvate into what?
Oxaloacetate. Pyruvate carboxylase requires biotin.
What cofactor is important in the carboxylation reaction of pyruvate to oxaloacetate?
Biotin
Why is the production of oxaloacetate from pyruvate important?
In order for the Krebs cycle to run
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
In which cells does the Krebs cycle not take place?
Rbc, as they lack 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 ketoglutarate
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 Krebs cycle?
The ratio of adp to atp
What does high levels of atp do to the Krebs cycle?
It slows it down
What coenzymes are needed in the Krebs cycle?
B3 as nad
B2 as fad
B5 to make Succinyl-CoA
Name four 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 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 conversion to malate
In what organs does gluconeogenesis occur?
Mostly liver but also kidney
Which hormone by its involvement with glucagon inhibits glycolysis and promotes gluconeogenesis?
Epinephrine. Glucagon is a hormone (made by the pancreas) that influences the liver to break down glycogen into glucose.
What steroid hormone promotes the gluconeogenic pathway?
Cortisol
Name 3 substrates for gluconeogenesis.
- Alanine (and other amino acids)
- Glycerol
- Lactate
What are the 2 key products of the hexose monophosphate shunt?
Nadph
Ribose (used in nucleotide synthesis)
What is the harvest from the Krebs cycle?
3 nadh
1 fadh
1 gtp
What is the key rate-limiting enzyme in glycogen synthesis?
Glycogen synthase
What hormone activates glycogen synthase?
Insulin
What hormones inhibit glycogen synthesis?
Cortisol, glucagon
What substance in low quantities inhibits glycogen synthase?
cAMP
Which tissues have high amounts of glycogen?
Liver and skeletal muscle
Which metabolite in glycolysis is tranformed 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 by the body?
It maintains iron as Fe2+ in RBCs
How many atp do you get from nadh?
Three
How many atp from fadh?
Two
Where does fadh enter the electron transport chain?
At ubiquinone
What mineral is important in the electron transport chain?
Iron
What is the overall harvest of energy from 1 molecule of glucose?
8 atp from glycolysis
2 nadh from pyruvate to acetyl SCoA
–> 6 atp
6 nadh –> 18 atp
2 fadh –> 4 atp
2 gtp –> 2 atp
Total of 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
How many carbons in a short chain FA?
2-6
How many carbons in a medium chain FA?
8-10
How many carbons in a long chain FA?
16-22
Animal fat is a good source of what type of FA?
Saturated
Oleic, linoleic and alpha linolenic acids are examples of what type of FA?
Unsaturated
Hydrogenation of fatty acids produces what?
Cis and Trans fatty acids
What are the 2 essential fatty acids?
Linoleic acid
Alpha linolenic acid
Essential fatty acids mean the human body can’t make it and thus must ingest it.
What is a good source of linoleic acid?
Vegetables, nuts and seeds
What is a good source for alpha-linolenic acid?
Flaxseeds
What is the name of the enzyme that converts linoleic and alpha-linolenic acids into their metabolites?
Delta-6-desaturase
Which efa is omega-3?
Alpha-linolenic acid
What efa is omega-6?
Linoleic acid
Which FA is the precursor for pro-inflammatory, series 2 eicosanoids?
Arachidonic acid. Series 2 eicosanoids produce prostaglandins. Arachidonic acid is also a precursor for series 4 eicosanoids which produce leukotrienes.
Which efa is precursor for series 1 eicosanoids?
Linoleic acid. Series 1 is correlated with inflammation.
Which efa is precursor for series 3 eicosanoids?
Alpha-linolenic acid. Series 3 is correlated with anti-inflammation.
Linoleic acid is converted by delta-6-desaturase into what fatty acid?
Gamma-linolenic acid
What are some good sources of gamma-linolenic acid?
Evening primrose oil, borage oil, blackcurrant oil
What important fatty acid, also known as 20:5(n-3) can alpha-linolenic acid be converted into?
Eicosapentaenoic acid
What is a good source of eicosapentaenoic acid?
Cold water fish oils
What is the name of the enzyme that releases arachidonic acid from cell membranes?
Phospholipase A2. Corticosteroids inhibit Phospholipase A2. Angiotensin II and epinephrine activate this enzyme.
What is the name of the enzyme that converts arachidonic acid into prostaglandins?
Cyclooxygenase aka COX. NSAIDs inhibit this event.
What is the name of the enzyme that forms leukotrienes from arachidonic acid?
Lipoxygenase
What products inhibit phospholipase A2?
Corticosteroid anti-inflammatories
What product inhibits activity of cyclooxygenase?
NSAIDs
What hormone promotes the conversion of carbohydrates into triglycerides?
Insulin
What enzyme causes the release of fatty acids from triglycerides?
Hormone sensitive lipase
What are free fatty acids usually bound to in the blood?
Albumin
What hormone inhibits action of hormone sensitive lipase?
Insulin
What promotes hormone sensitive lipase?
Growth hormone, glucagon and Epi
Esterification is used in the forming of triglycerides from what 2 substances?
Acetyl-CoA and glycerol-6-phosphate
Free fatty acids are mobilized from what cell?
Adipose
What is the action of lipase?
It breaks down ester bonds
What is the optimal pH for gastric lipases?
4.5 to 6.0
Where does lipolysis of dietary triglycerides occur?
20-30% in the stomach, 80-70% in the small intestines
What constitutes a triglyceride?
3 Fatty acids attached to a glycerol backbone
Lecithin or phosphatidylcholine is found in what substance?
Phospholipids
What mineral is important in cell membranes?
Phosphorus. Lecithin (which contains phosphorus) is an integral component for cell membrane production.
What does saturated refer to?
All carbons of a fatty acid are saturated with hydrogens so no double bonds. Versus unsaturated means it contains at least 1 double or triple bond.
Double bonds are seen in what kind of FA?
Unsaturated
How are lipids transported in the blood?
Via lipoproteins. Versus TAG travels in general circulation via chylomicrons.
What are 2 effects of trans-fatty acids on the body?
- Interfere with essential fatty acid metabolism
- Atherogenesis
What substance emulsifies FAs?
Bile. Bile salts are amphipathic and thus can turn larger fat globules into smaller ones. This allows more surface area for lipase to impact on.
How do triglycerides cross the intestinal membrane?
They drop 2 fatty acids leaving one at the number 2 site on glycerol, cross membrane and get reformed on the other side
How do triglycerides travel in general circulation?
Via chylomicrons in the lymphatics and blood stream. Versus lipids are transported in the blood by lipoproteins.
Where does beta oxidation take place?
In the mitochondrion of all cells. Versus fatty acid synthesis occurs in the cytosol.
What is the activated form of FA?
Acetyl-CoA
How is Acetyl-CoA transported into the mitochondrion?
Via carnitine
What co-enzyme is needed in the activation of FA into Acetyl-CoA?
Vitamin B5
What co-enzymes are needed in the beta-oxidation pathway?
Vitamin B2 as fad
Vitamin B3 as nad
Where does FA synthesis take place?
In cytosol of all cells
What is the rate-limiting enzyme of FA synthesis?
Acetyl-CoA carboxylase
What is the immediate substrate for FA synthesis?
Acetyl-CoA
Acetyl-CoA carboxylase acts on Acetyl-CoA to produce what?
Malonyl-CoA
What co-enzyme is important for the production of Malonyl-CoA from Acetyl-CoA?
Biotin
What reducing agent is used in FA synthesis?
Nadph
How does Acetyl-CoA get out into the cytoplasm for FA synthesis?
Citrate leaves the mitochondrion and the action of citrate lyase forms Acetyl-CoA and oxaloacetate
What hormone activates Acetyl-CoA carboxylase?
Insulin
What is the end product of de novo FA synthesis?
Palmitate. De novo means to make new.
What substance is the activated end product of lipogenesis and will cause feedback inhibition on Acetyl-CoA carboxylase?
Palmitoyl-CoA
What 3 tissues undergo lipogenesis?
Liver, skeletal muscle, and cardiac muscle
Where does chain elongation take place?
In the mitochondrion and smooth ER
Which tissues undergo de novo synthesis?
Liver and adipose cells
Where does de novo synthesis take place?
In the cytoplasm
What are the 3 Ketone Bodies?
Acetoacetate, acetone and beta hydroxybutyrate
Ketone production takes place when which substance is low?
Oxaloacetate
In what tissue does ketone synthesis take place?
Liver
Where in the cell does ketone synthesis take place?
In the mitochondrial matrix
What is the fate of acetone?
It is usually exhaled
What is the fate of 3 hydroxybutyrate?
It gets oxidized to acetoacetate
What 2 tissues can use acetoacetate?
Brain and skeletal muscle
What apoprotein marks hdl for hepatic uptake?
Apoprotein E
How is dietary fat carried into the body?
In chylomicrons via the lacteals
Which tissues synthesize chylomicrons?
Mucosal cells of small intestine
Apoprotein A is found on what lipoprotein?
hdl
Which lipoprotein functions to carry triglycerides from the liver to extrahepatic tissue?
vldl
Which lipoprotein functions to carry cholesterol from liver to extrahepatic tissue?
ldl
Which apoprotein allows for uptake of cholesterol by cells?
Apoprotein B
Chylomicron remnants are formed from the action of which enzyme?
Apoprotein lipase
What enzyme facilitates cholesterol transfer to hdl from tissues?
Lecithin-cholesterol acyltransferase
What apoprotein activates Lecithin-cholesterol acyltransferase?
Apoprotein A on hdl
Which transfer protein facilitates transfer of cholesterol from ldl and vldl to hdl?
Cholesterol transfer protein
In which tissues does cholesterol synthesis take place?
Liver and intestines
Where in the cell does cholesterol synthesis take place?
Cytoplasm
What is the precursor for cholesterol synthesis?
Acetyl-CoA
What pathway is the greatest producer of Acetyl-CoA?
Beta-oxidation
What is the rate-limiting, regulatory enzyme of cholesterol synthesis?
hmg-CoA reductase
What hormone promotes the action of hmg-CoA reductase?
Insulin
What are the 2 significant intermediates in cholesterol synthesis?
hmg-CoA and mevalonate
What is the function of cholesterol?
Membrane fluidity, precursor to all steroid hormones
What type of fatty acids increase cholesterol? Which decrease it?
Increase: Saturated fats
Decrease: Unsaturated fats
What are the 2 primary bile acids?
Cholic acid
Chenodeoxycholic acid
Primary bile acids are made by the liver.
What are the 2 secondary bile acids?
Deoxycholic acid
Lithocholic acid
Secondary bile acids are produced by bacteria in the colon.
Where are bile acids formed?
Liver and intestines
Where are bile acids stored?
Gallbladder
Where does bile acid reabsorption take place?
Ileum
What are the 2 functions of bile acids?
Fat emulsification
Cholesterol excretion
What metabolite is formed from mevalonate?
CoQ10
What 2 hormones are released in response to fatty chyme reaching the duodenum?
Secretin and Cholecystokinin
What hormone secreted from the intestines is responsible for increasing bile production in the Liver and stimulating bile secretion from the liver?
Secretin
What hormone produced by the intestines stimulates the hepatopancreatic sphincter to relax, stimulates secretion of pancreatic juices, and cause the gallbladder to contract and release bile?
Cholecystokinin (CCK)
What role do bile salts play in fat absorption?
They emulsify fats to enhance their absorption
What 2 substance acts as a conjugating agents to convert bile acids into bile salts?
Taurine and glycine
What enzyme is the rate limiting step in bile acid formation?
7-alpha-hydroxylase
What vitamin is needed for the activity of 7-alpha-hydroxylase?
Vitamin C
Testosterone is produced in which tissues?
Adrenal cortex, testes
Estrone and estradiol and produced in which tissue?
Ovaries and small amount in adrenal cortex
Dhea, progesterone, cortisol and aldosterone are produced in which tissue?
Adrenal cortex
What is precursor for steroid hormones?
Cholesterol
What vitamin is needed for steroid hormone production?
Vitamin C
Trytophan is a precursor for what neurotransmitters?
Serotonin and melatonin
The reaction of trytophan to serotonin requires what vitamin as a co-factor?
Vitamin B6 (pyridoxine)
Tryptophan can also be turned into what molecule?
Niacin
Tyrosine is the precursor for which three neurotransmitters?
Dopamine, norepinephrine and epinephrin. These are catecholamines.
What is the rate limiting cofactor in the conversion of tryptophan to 5-hydroxytryptophan, phenylalanine to tyrosine, and tyrosine to dopamine?
5-methyltetrahydrofolate (active folic acid)
What is the rate-limiting enzyme for the production of L-dopa (and therefore catecholamines in general) from tyrosine?
Tyrosine hydroxylase
What factors inhibit and promote the activity of tyrosine hydroxylase?
Promotes: Cold, stress
Inhibits: Norepi
What vitamin is needed as a cofactor for the production of norepi from dopamine?
Vitamin C
What is the name of the enzyme that breaks down norepi and epinephrine?
Monoamine oxidase (mao)
What is the breakdown product of mao’s action on norepi and epi?
Vanillylmandelic acid (vma)
What are the 3 branched chain amino acids?
Valine, isoleucine and leucine
Post-translational modification of proline and lysine to form hydroxylysine and hydroxyproline in collagen formation requires which vitamin?
Vitamin C
Which 3 amino acids can be post-translationally modified by phosphorylation?
Serine
Threonine
Tyrosine
Gaba (Gamma-aminobutyric acid) is formed from what amino acid?
Glutamate/glutamic acid
The conversion of glutamic acid to gaba requires what vitamin as a cofactor?
Vitamin B6 (pyridoxine)
Histamine is formed from what amino acid?
Histidine
Which amino acid is the main methyl donor in the body?
Methionine
What are the 6 amino acids that can be catabolized by skeletal muscle?
Valine
Aspartic acid
Leucine
Asparagine
Isoleucine
Glutamic acid
What are the 3 amino acids that make up the tripeptide glutathione?
Cysteine, glycine and glutamic acid
What are the 2 initial precursors for heme synthesis?
Glycine and Succinyl-CoA
What 2 amino acids form cysteine?
Glycine and arginine
What amino acid is the main transporter of nitrogen (ammonia) in the blood?
Glutamine
Alanine can be converted into what substance?
Pyruvate
What amino acid is a major component of actin and myosin? What form does it take?
Histidine in the form of 3-methyl-histidine
What type of bond holds together the amino acid sequence of peptides?
Covalent. Covalent bonds involve electron sharing.
What are the only 2 sulphur-containing dietary amino acids?
Methionine and cysteine
What 2 bonds hold a secondary protein structure?
Disulfide and weak
3-D folding of proteins is seen in which structure?
Tertiary
2 or more single polypeptide chains bonded by weak bonds is called what?
Quaternary structure
The heme molecule is an example of what type of protein structure?
Quaternary
2 Cysteine residues can form what type of bond?
Disulfide
A water-soluble protein is known as what?
A globular protein
Hydrogen bonds, salt bridges (or ionic attraction) and hydrophobic interactions are classified as what type of bond?
Weak
Atoms that share 1 or more electrons are bonded by what type of bond?
Covalent
What are the 10 essential amino acids?
Threonine, lysine, valine, leucine, methionine, tryptophan, phenylalanine, histidine, isoleucine, arginine.
The removal of an alpha-amino group from an amino acid is the first stage in amino acid catabolism and is known as what?
Transamination
Catabolism of amino acids uses what 2 types of reaction?
Oxidative deamination and transamination
The effect of transamination reactions is to collect the amino groups from all the other amino acids in the form of only one amino acid, which one?
Glutamate
Transaminases require what vitamin as a cofactor?
Vitamin B6, pyridoxine
In which tissues does oxidative deamination occur?
In the liver and kidneys
In what part of the cell does oxidative deamination take place?
The mitochondria
What is the main amino acid to undergo oxidative deamination?
Glutamate
What is the main enzyme in oxidative deamination?
Glutamine dehydrogenase
Which amino acid is present in blood in the highest levels?
Glutamine. It is the major carrier of amino groups. It allows transport of toxic nitrogen in a non-toxic form from extrahepatic tissues to the liver.
Glutamine synthetase is the enzyme that catalyzes the reaction of glutamate into glutamine. Its levels are especially high in which tissue?
The brain, as it is especially sensitive to ammonia. Glutamine synthetase regulates glutamate levels in the brain. It is mostly found within astrocytes.
Which amino acid transfers ammonia from muscle to the liver?
Alanine
Urea is formed from what 2 molecules?
CO2 and ammonia
Where does the urea cycle take place?
The liver
How is the urea cycle regulated?
Substrate availability, i.e. dietary protein
Where do the 2 nitrogen atoms in urea come from?
One from ammonia and one from aspartate
Which Krebs cycle intermediate is produced by the urea cycle?
Fumarate
What are the 4 major constituents of urine?
Urea, ammonia, creatinine and uric acid
What is the role of hcl in protein digestion?
To denature the protein and provide optimal pH for pepsinogen conversion to pepsin
What enzyme has optimum activity at pH2?
Pepsinogen which is converted into pepsin
What three aromatic amino acids have their peptide bonds hydrolyzed by pepsin?
Tyrosine, phenylalanine and tryptophan
Enterokinase is the enzyme that activates which zymogen released by the pancreas?
Trypsinogen
Which enzyme activates all the other zymogens released by the pancreas?
Trypsin
What is the overall fate of proteins that we eat?
They form free amino acids and enter the liver via the portal blood supply
What is the role of brush border enzymes in protein digestion?
They break down the smaller peptides to release free amino acids which are transported across the epithelial cells and enter blood capillaries
Which bonds need to be broken for a protein to become denatured?
Weak and disulfide bonds
What are the building blocks of nucleic acids called?
Nucleotides
What are the 3 characteristic components of a nucleotide?
Nitrogenous base (purine or pyrimidine), a pentose sugar (ribose or deoxyribose) and a phosphate group.
A nucleotide minus the phosphate group is known as what?
A nucleoside
What kind of bond joins nucleic acids in RNA and DNA?
3’,5’ unequal -phosphodiester bonds
Where does purine and pyrimidine synthesis occur?
In the liver
What other tissue produces significant quantities of purine and pyrimidine?
The brain
What metabolic pathway produces ribose residues for nucleic acid synthesis?
Hexose monophosphate shunt
What molecule is the precursor for adenine and guanine?
IMP or inositol monophosphate. Adenine and guanine are purines.
What molecule is the precursor for cytosine, uracil, and thymine?
UMP or uridine monophosphate. Cytosine, uracil, and thymine are pyrimidines.
What are the precursors for pyrimidine synthesis?
Glutamine and CO2
What is an important co-enzyme in purine and pyrimidine synthesis?
Folic acid
In de novo synthesis of purines what is the starting material?
Ribose-5-phosphate
What does DNA stand for?
Deoxyribonucleic Acid
What makes RNA different from DNA?
Smaller strand of genetic information
No de-oxy sugar
Contains uracil, not thymine
What are the 3 different types of RNA?
mRNA - Messenger RNA
tRNA - Transport RNA
rRNA - Ribosomal RNA
What is the function of tRNA?
To bring the correct amino acid in line with the correct codon
What is the function of mRNA?
It carries the genetic sequence information from the genes to the ribosome to be coded
What is the function of rRNA?
Aids transfer RNA in translation
Making RNA from a DNA template is known as what?
Transcription
Regarding RNA and DNA what does translation mean?
It the process by which the information from mRNA is decoded and used to assemble the polypeptide
What factors can separate DNA strands?
An increase in temperate
Changing the salt concentration around it
Salt neutralizes the charge on the sugar phosphate backbone of DNA (making it less hydrophilic).
Heat can denature the DNA strands.
Three consecutive base pairs are known as what?
A codon
What are the four nucleotide bases that make up DNA?
Adenine,
Guanine,
Cytosine,
Thymine.
What are the 2 pyrimidines found in DNA?
Cytosine and Thymine
What are the 2 pyrimidines found in RNA?
Cytosine and Uracil
What are the 2 purines in RNA and DNA?
Adenine and Guanine
Adenine pairs with which other nucleotide bases?
Thymine, Uracil
Cytosine pairs with which base?
Guanine
Where does pyrimidine and purine catabolism occur mainly?
The Liver
In RNA what nucleotide base stands in for thymine?
Uracil
Purine degradation generates what molecule?
Uric acid
Pyrimidines are degrade into what molecules?
Carbon dioxide and water
What is the name for the last enzyme in the production of uric acid from purines?
Xanthine oxidase
What mineral is needed as a cofactor in the conversion of purine into uric acid?
Molybdenum
What do enzymes do in chemical reactions?
They lower the activation energy of a reaction and increase the rate of the reaction
What 2 things affect enzyme activity?
pH and temperature. pH changes may affect the shape and charge of both enzymes and substrates (so it can’t bind to active sites). Temperature increases reaction rates.
The synthesis of an enzyme needed for breakdown of a certain substrate is initiated by the presence of that substrate is known as what?
Induction
Modulation of an enzyme by the non-covalent binding of a specific metabolite at a site other than the active site is an example of what?
Allosteric activity
Molecules that must undergo cleavage reactions in order to become active are known as what?
Zymogens. Examples of zymogens are angiotensinogen, trypsinogen, and pepsinogen.
Substances that hold an enzyme in certain configurations so that it can function are known as what?
Co-factors or co-enzymes
Phosphorylation or dephosphorylation of an enzyme is an example of what?
Covalent modification
An enzyme bound to its co-enzyme is known as what?
An holozyme
Multiple forms of an enzyme that catalyze the same reaction but differ from each other in amino acid sequence, substrate affinity and regulatory properties are known as what?
Isozymes
Vitamin B1 is known as what?
Thiamine. Deficiency in Vitamin B1 can manifest as Beriberi.
What is the active form of B1/thiamin called?
Thiamin pyrophosphate
What mineral is often required in reactions involving vitamin B1/thiamin as a cofactor?
Magnesium
Transketolase in the hexose shunt requires what vitamin?
Vitamin B1 (thiamin)
Where is vitamin B1 (thiamin) absorbed?
Jejunum or ileum
Vitamin B2 is known as what?
Riboflavin. Deficiency in Vitamin B2 can manifest as glossitis or seborrhea.
Where is vitamin B2 (riboflavin) absorbed?
Duodenum or jejunum
Vitamin B3 is known as what?
Niacin or nicotinic acid. Deficiency in Vitamin B3 can manifest as Pellegra.
Vitamin B5 is known as what?
Pantothenic acid. Deficiency in Vitamin B5 can exhibit a phenomenon called burning feet.
Vitamin B6 is known as what?
Pyridoxine. Mg is needed to activate this vitamin. Deficiency in Vitamin B6 can induce dermatitis.
Vitamin B12 is known as what?
Cobalamin
Oxidative carboxylation in the pyruvate dehydrogenase complex needs what vitamin?
Vitamin B1 (thiamin), vitamin B2 (fad), vitamin B3 (nad), and vitamin B5 (CoA)
What vitamin plays a role in transamination reactions?
Vitamin B6 (pyridoxine)
Fad and fmn are active constituents of what vitamin?
Vitamin B2 (riboflavin)
What vitamins are used in oxidation-reduction reactions/ electron transfer reactions (dehydrogenase enzymes)?
Vitamin B3 (niacin) and vitamin B2 (riboflavin)
What form of niacin is used in synthesis pathways?
nadph
Nad and nadh are the oxidized and reduced forms of what vitamin?
Vitamin B3 (niacin)
What amino acid can form niacin?
Tryptophan
Where is pantothenic acid absorbed?
Jejunum
Which vitamin is essential for reactions using CoA?
Vitamin B5 (pantothenic acid)
Pyridoxal phosphate is the active form of what vitamin?
Vitamin B6 (pyridoxine)
What mineral is needed to activate vitamin B6?
Magnesium
Which vitamin serves as CO2 carrier in carboxylation reactions?
Biotin
Which vitamin is essential for nucleotide synthesis and for single carbon transfer?
Folic acid
What vitamin is needed as a co-factor to activate folic acid?
Vitamin B12 (cobalamin)
What is the first active form of B12?
Methylcobalamin
List some of the biochemical activities of Vitamin C
(1) Reducing agent
(2) Co-factor for hydroxylation reactions eg. proline, dopamine and norep/epi synthesis
(3) Carnitine synthesis
(4) Enhances iron mobilization
(5) Bile acid formation
(6) Influence on cholesterol metabolism
What is the active form of vitamin A in the blood?
Retinol
What is the active form of vitamin A in the eyes?
Retinal
What is the active form of vitamin A in epithelial cells?
Retinoic acid
This mineral is a constituent of dna and rna.
Phosphorus
Which vitamin is a co-factor in post synthetic modification of proteins via a carboxylation reaction, which allows for the chelation of calcium?
Vitamin K
What is the storage form of vitamin A in the liver?
Retinyl palmitate
Where is vitamin A absorbed?
Lumen of S.I.
Which of the active forms of vitamin D increases serum calcium?
1,25-(OH2)D3
Which of the active forms of vitamin D lowers serum calcium?
24,25-(OH2)D3
Where are the inactive metabolites of vitamin D converted to active form?
Kidney primarily, also in neurons, leukocytes, and other peripheral tissues
Which hormone plays a role in activating vitamin D?
Parathyroid hormone
Where is vitamin E stored?
Adipose tissue
Fat soluble-vitamins, like Vit E, depend on what for their absorption from the intestinal lumen?
Pancreatic esterases and bile salts
What converts 7-hydroxycholesterol into cholecalciferol?
Sunlight on the skin
Beta-carotene is a precursor to what vitamin?
Vitamin A
What vitamin is required for the biosynthesis of clotting factors?
Vitamin K
What is the active form of vitamin K?
Hydroquinone
Which mineral is important for energy-producing reactions?
Phosphorous
The production of osteocalcin is dependent on what vitamin?
Vitamin K (which is needed for carboxylation)
What mineral is important for clotting?
Calcium. It plays a vital role in protein structure and function in clotting.
This mineral, once it is attached to a substance, traps it inside the cell.
Phosphorous
All the reactions using atp use this mineral as a cofactor.
Magnesium
This mineral activates a number of B vitamins.
Magnesium
Which mineral is the most abundant intracellularly?
Potassium
What mineral is in cytochromes?
Iron
Which mineral is an insulin cofactor?
Chromium
Which mineral is a part of glutathione peroxidase?
Selenium
Which mineral is a part of vitamin B12?
Cobalt. Vitamin B12 is also known as cobalamin.
Which mineral is important for the biosynthesis of thyroid hormones?
Iodine
Which mineral is needed for cholesterol synthesis?
Manganese
What is the blood transport form of iron?
Transferrin
What is the main storage form of iron?
Ferritin
What stores excess iron?
Hemosiderin
What substance is protective in that it keeps iron away from bacteria?
Lactoferrin
What are the 3 sources of glucose in the body?
Gluconeogenesis, dietary, and glycogen breakdown
How is glucose transported in the body?
Free
Glycogen is formed in all tissues but especially which 3?
Liver, cardiac and skeletal muscle
Complete oxidation means what?
The complete breakdown of carbohydrates, proteins or fatty acids into atp, CO2 and water.
Incomplete oxidation or anaerobic glycolysis forms what substance?
Lactate
Excess glucose is converted to what?
Fatty acids especially in adipose and liver
What are the 2 sources of blood triglycerides?
Diet and synthesis by liver and mucosal cells of intestine
How are dietary triglycerides transported?
By chylomicrons
How do triglycerides travel from liver into the blood?
Via vldl
True or false: Triglycerides can cross membranes.
False, they need lipoprotein to cross membranes
What kind of bonds does lipoprotein lipase break?
Ester bonds. Lipoprotein lipase catabolizes TAG.
What is the fate of triglycerides?
They get broken down by lipoprotein lipase and free fatty acids are released
How are free fatty acids transported?
Via albumin in the blood
What are the 2 sources of blood cholesterol?
Diet and synthesis by liver
Blood levels of cholesterol are mainly affected by what?
Liver synthesis
What are the 2 main carrier proteins in the blood?
Albumin
Globulin
Albumin carries insoluble molecules like fatty acids, steroids, and thyroid hormones. Globulin carries lipids and fat soluble vitamins/minerals.
What enzyme catalyzes the conversion of lactate into pyruvate?
ldh (Lactate Dehydrogenase)
How many ldh isoenzymes are there?
Five
What enzyme catalyzes the conversion of creatine into creatine phosphate?
cpk (Creatine Phosphokinase)
What enzyme transfers an amino group from alanine to alpha-ketoglutarate?
alt or sgpt
What enzyme transfers an amino group from glutamate to oxaloacetate to form aspartate?
ast or sgot
What are the major sources for sgot/ast?
Cardiac tissue
Liver
Skeletal muscle
RBCs
What are the major sources for sgpt/alt?
Highest concentration in the liver
Also found in the heart, skeletal muscle, and RBCs
Glucokinase, hexokinase, phosphofructokinase and pyruvate kinase are found in which pathoway?
Glycolysis
Which enzyme, when turned on, allows Acetyl-CoA to be used for gluconeogenesis?
Pyruvate Carboxylase. Carboxylase enzymes add carboxyl groups.
Which enzyme, when turned on, allows Acetyl-CoA to be used for atp production?
Pyruvate dehydrogenase complex. Dehydrogenase enzymes remove hydrogen atoms.
Glucose-6-phosphatase, fructose 1,6-bisphosphatase and pyruvate carboxykinase are found in what pathway?
Gluconeogenic pathway
Carnitine is found in which pathway?
Lipolysis/beta oxidation
Palmitoyl-CoA is found in which pathway?
Lipogenesis
Malonyl-CoA is found in which pathway?
Lipogenesis
Acetyl-CoA carboxylase is found in which pathway?
Lipogenesis
Ubiquinone and cytochromes are found in which pathway?
Electron transport chain
Citrate lyase is found in which pathway?
Lipogenesis
Delta-6-desaturase is found in which pathway?
Eicosanoid production pathway
Phospholipase A2 is found in which pathway?
Eicosanoid production from arachidonic acid
Cyclooxygenase is found in which pathway?
In the prostaglandin synthesis pathway from arachidonic acid
Hmg-CoA reductase is found in which pathway?
Cholesterol synthesis
7 alpha hydroxylase is found in which pathway?
Bile synthesis
Mevalonate is found in which pathway?
Cholesterol synthesis
