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BIOCHEMISTRY (CHEM 212) EXAM 3 - STUDY GUIDE
2025 - 2026. ACTUAL EXAM QUESTIONS WITH CORRECT
DETAILED ANSWERS/PORTAGE LEARNING
Origins of energy
● From the sun ● Have to use plants as an intermediary attempt ● Creates carbohydrates that we can get energy
- Glucose, use oxygen to help conbust ● In plants: photosynthesis ● In human bodies: cellular respiration
- Opposite reactions
Energy Requirements For Life
● Energy must be released from food gradually ● Energy must be stored in a readily accessible form ● Release of energy from storage must be finely controlled so that it is available exactly when and where it is needed ● Just enough energy must be released to maintain body temperature ● Energy in a form other than heat must be available to drive chemical reaction that are not favorable at body repretures
Metabolism
● Metabolism: All chemical reactions that take place in an organism ● Catabolism: process that breakdown food (lipids, carbohydrates and proteins) to produce energy ● Anabolic: process that requires energy to build molecules from small ones ● Yellow is catabolic, blue is anabolic
● Stages of catabolism:
- DIgestion of macromolecules into subunits ❖ Lipids into fatty acids and glycerol ❖ Carbohydrates into glucose and other sugars ❖ Proteins into amino acids
● TCA
● 6 dif enzymes,
Spiral Sequence
● One enzyme or group of enzymes breakdown a polymer one moner at a time ●
High energy Molecules
● Coenzymes
- Acetyl-SCoA: high energy form ❖ Coenzyme A ❖ Function as carrier of acetyl groups (2 carbon groups into TCA cycle) ❖ Vitamin: Pantothenic Acid
- NADH ❖ NAPPH is a derivative, has addition of PH ❖ Derived from Niacin ❖ NAD+ and NADP+ is low energy form ❖ NADH and NADPH high energy form ❖ Used in redox reactions
- FADH ❖ ADAH2 is high energy form ❖ FAD is low energy form, oxidized ❖ Vitamin: riboflavin ❖ Used in redox reactions
- An organic compound that is required for catalysis
- Derived from water soluble vitamins ● ATP
- Energy currency of cell
- Delta g is 7.3 kcal/mol
- Considered an energy store
- Stable at ph 7
- Requires an enzyme for hydrolysis: other anhydrides break down in water
- Easy bond to leave: negative charge on O repel each other so bonds are strained
- Precursor for other high energy molecules
- Uniersial energy works in all cells
- People typically generate and consume 3 moles of ATP/hr ● Endergonic reaction coupled with exergonic reaction to achieve a total free energy charge that is negative
Classification of Carbohydrates
● Carbohydrate
- A member of a large class of naturally occurring polyhydroxy ketones and aldehydes ● Monosaccharide (simple sugar)
- A carbohydrate that cannot be chemically broken down into a smaller sugar by hydrolysis with aqueous ……. ● Disaccharide
- A charboydiriate composed of two monosaccharides
- covalent bonds ● Polysaccharide (complex carbohydrate)
- A carbohydrate which is a polymer of monosaccharides ● Aldose
- A monosaccharide that contains an aldehyde group
- Ends in alcohol group
- Glucose: blood sugar ● Ketose
- A monosaccharides that contains a ketone group
- Ends in alcohol group
- Fructose: fruit sugar ● Names ending in - ose indicates a carbohydrate
Isomers of Carbohydrates
● Isomers are compound with the same molecular formula but different 3D structure ● D and L isomers (enantiomers)
- Monosaccharides that are mirror images of one another
- D form of all monosaccharides is the most prevalent in nature
- D: OH group on last chiral carbon is on the right side
- L: OH group is on the left side ● Diastereomers
- Diastereomers: stereoisomers but not mirror images of one another
of isomers is 2 to the n
- Whatever carbon is bonded to the Oh group on fisher projection, is the anomeric carbon...determines where the hhh gets trapped ❖ Alpha vs beta form
- Hemiacetal: a carbon atom bonded to both and OH and OR group ● Anomers
- A monosaccharide has alpha and beta isomers that occur in different ratios in nature. The beta form of glucose is most prevalent in nature Reactions of Carbohydrates
● Can be a possible receptor ● Will either bind to a Asn or Ser or Thr residue ● Carbohydrates determine blood type
- Will bind in certain configuration that makes the different blood groups
- They have different groups which explain the inability to transfuse different blood groups
- AB is the universal recipient
Cellulose
● Most abundant polysaccharide in the world ● Beta-d-glucose units linked by b1,4 glycosidic bonds ● Fibrous substances that provides structure in plants ● Humans do not have enzymes that is necessary to hydrolyze cellulose ● Buct can be digestible as indigestible fiber ● Als used to make material for houses, paper, cardboard
Plants starches
● Amylose:
- 20% of plant starch
- Polymer of a-1,4 D-glucose
- Fully digestible polymers of glucose
- Present only in plants ● Amylopectin
- 80% of plant starch
- Energy storage in seeds
- Polymer of a-1,4 D-glucose with branches at a-1,6 D glucose
Glycogen
● Found in animals ● energy storage (liver and muscles) ● Similar to amylopectin found in plants ● But it has more branches and is much larger
Carbohydrate digestion
● In second section, a pancreatic a-amylase is produced ● In third section, absorption and through small intestine ● Glycolysis: conversion of glucose to pyruvate ● Gluconeogenesis: synthesis of glucose from amino acids, pyruvate, and non-carbohydrates ● Glycogenesis: synthesis of glycogen from glucose ● Glycogenolysis: breakdown of glycogen to glucose ● Pentose phosphate Pathway: conversion of glucose to five carbon sugar phosphates ●
Glycolysis
● Energy investment phase (steps 1 - 5)
- Investing 2 molecules of ATP getting out 4 molecules of ATP ● Energy generation phase (6-10)
- Generation of a super-high=energy compound Production of 2 ATPs
- Pathway for synthesis of glycogen
- Occurs when there's excess amount of glucose 6 phosphate ● Glycogenolysis
- The pathway for breakdown of glycogen to free glucose
- Occurs in muscle cells when there is an immediate need for energy
- Occurs in the liver when blood glucose levels are low
Signalling cascade
- Messenger moleuve or neurotransmitter
- Binds to certain cell to turn it on and signal
- Hormone binds to surface of the cell to signal a biochemical response
- Inulin replenishes energy stores and glucagon breaks down energy stores to make new glucose
- Glucose is gone so secrete glucagon
- Pancreas: sensus blood glucose levels and releases according hormos
- Liver: release or extracts glucose from the blood
Glucagon/epinephrine
● Hormone that when bound to receptors on the surface of cell cause activation of adenylate cyclase within the cell ● Glucagon is a peptide hormone whose main site of action is liver ● epinephrine/adrenaline is an amino acid derivative with receptors mainly on muscle ● Both signaling cause glycogen to breakdown, glucose to be synthesized and blood glucose levels to increase ● Accomplished by
- Phosphorylated glycogen synthase to deactivate it (MAKES IT)
- Phosphorylated glycogen phosphorylase to activate (BREAKS DOWN)
Insulin
● Insulin is a protein hormone whose receptor is a pryose kinase present in most cells ● It signaling causes glycogen to be synthesized and blood glucose levels to decrease ● Accomplished by
- Phosphorylated glycogen synthase to activate
- Dephosphorylation glycogen phosphate to deactivate it
Regulation of glycogen synthase
● Starts with hexokinase ● In liver NOT feedback inhibited by glucose - 6 - P ● Isomerase brings next step to compilation ● Regulation of glycogen synthase
- Non hormonal: glucose- 6 - P is a positive allosteric regulator
- Hormonal: epinephrine and glycogen inhibits glycogen synthesis
- Insulin stimulates glycogen synthesis ● ● Glycogen storage diseases
- Von gierke's disease: glucose - phosphate deficiency
- Enlarged liver
- Dangerously low blood sugar ● Mcardles
- Muscle glycogen defincues
- The normal pancreas in plasma lactate following exercise is absent
- Muscles are damaged because of inadequate energy supplies and glycogen accumulation blood analysis shows increased levels of creatine phosphokinase, aldolase, myoglobin ● Pentose Phosphate Pathway ● AN alternate pathway for carbohydrate oxidation ● Anabolic role ● Primary functions is to provide NADPH for biosynthesis pathways
- The provide ribose 5 - phosphate for nucleic acid biosynthesis
- Occurs when cell is dividing
- Metabolism of dietary pentose sugars ● Cori Cycle
● Chosestoreal
- Ridged ring like structure ● Prostaglandin
- 20 carbon unit
- Contractions are due to type of prostaglandin Fatty Acids ● Saturated fatty acids
- Long alkane
- A Long chain carboxylic acids containing only C-C single bonds
- Beta carbon will be catalyzed
- Can pack together very densely
- No double bonds
- Chains pack together as a result of hydrophobic interactions and van der waal forces ● Unsaturated fats
- A long chain carboxylic acid containing one or more C-C double bonds
- Unsaturated fatty acids: one double bonds
- Polyunsaturated fatty acids: have more than one c-c double bonds
- Cis is naturally occuring unsatuated fatty acids
- Because of kinks, cant pack together
- Have low melting points
- Linoleic are two essential unsaturated fatty acids ● What determines the melting temp
- Chain length: the longer the carbon chain the higher the melting temp
- Degree of saturation: the more double bonds the lower the melting temperature Fat vs. Oil ● Two types of TAG’s: fat and oil ● Non polar, hydroponic, non ironic ● Animal fat contains more saturated fats than plant oil ● Because of the high degree of saturation in animal fat, it is a solid at room temp
● Because of the higher content of unsaturated fatty acids in plant oil it is commonly liquid at room temperature ● Double bonds in naturally occurring fatty acids are always “cis” in configuration ● Form of the double bonds in unsaturated are CIS
Reactions with triglycerides
● Saponification: hydrolysis of fats and oils carried out by strong aqueous bases to form soaps
- Fat → boil in presence of sodium hydroxide and makes glycerol and fatty acids salts
- Laundry detergent is anionic
- Non ionic - cold water/sanitizers/toilet bowl cleaners
- Catonic is fabric softener ● Hydronigation
- Unsaturated fatty acid to saturated fatty acid
- Ionine number=the number of grams of iodine which will react with 100g of fat or oil
- Higher the ionization number the more double bonds
- Trans fats are byproducation of of trans fatty acids
- Trans fatty acids do not exist in nature, increases LDL and decreases HDL and increases coronary heart disease
Cell membranes
● Phospholipids
- Hydrophobic region and hydrophilic region
- X can be replaced with choline, serine, and ethanolamine
- Also can be replaced with sugar (inositol) ● Phospholipids congreates away from water
Cholesterol
● Four fused rings ● Our bodies can synthesize cholesterol ● Synthesized from acetyl CoA ● Precursor for steroid hormones, vitamin D, and bile ● 50% found in cell membranes Biosynthesis of fatty acid ● Link between carbohydrates, lipid, and protein metabolism
Lipid transport in the blood
● Lipoprotein: lipoprotein contains a core of neutral lipids, including triacylglycerols and cholesterol esters ● Starting the core is a layer of phospholipids in which the varying proportions of proteins and cholesterol are embedded ● ● Density and composition of lipoproteins: based on amount of proteins they have within them ● Chylomicrons: transports dietary lipids ● VLDL: transport of synthesized TAGS ● LDL: transport of endogenous lipids (cholesterol) to the tissues (receptor mediated) (bad)
● HDL: Transport of lipids and cholesterol from cells in the vasculature to liver (good) ● VLDL and LDL ---> atherogenic ● HDL is anti-atherogenic
TAG Metabolism
● Storage of TAGS is regulated by insulin and glucagon ● Storage and synthesis of TAGS: high levels of insulin stimulate TAG synthesis
- Step 1: glycolysis produces DHAP
- Mobilization (hydrolysis) of TAGS: low insulin levels and high glycogen levels simulate triacylglycerol lipase in adipocytes
Fate of Fatty Acid in Cell
● Activation of FA by the addition of CoA: energy cost 2 ATPs ● Can be converted into TAGS, cholesterol, or phospholipids ● Bnds to carnitine for transport into mitochondrial matrix via pore formed by large enzyme complex ● Oxidation of FA with even number of carbon to acetyl-SCoA ● ●
Ketone Bodies and Ketosis
● Increase in FA breakdown causes increase in Acetyl-SCoA, which overlaps the citric acid cycle causing the production of ketone bodies
● Thrombosis a blood clot that forms in blood vessel ● ● Prevention
- Lower cholesterol: form diet and synthesis ❖ Cholesterol is only found in animal products
- Increase HDL levels ❖ Aerobic exercise, women have high levels
❖ Lose weight ❖ One glass of alcohol/day ❖ Eat more unsaturated FA instead of saturated
Protein Metabolism
● Protein digestion
- Comes from diet
- Put into mouth and chew
- In stomach, ph (2) of stomach breaks down covalent bonds and potent unfolds
- Peptin brakes more bonds
- Small intestine signals releases of protease, more bonds are chewed
- Amino acids are released into bloodstream ● Proteins through digestion dn old proteins from cells are broken down into amino acids to form amino acid pool ● Pool amino acids can either got to cells to form new proteins of they are broken down into the following ● Fate of the amino group
- Step 1: transamination ❖ Amine group is transferred to a-keto acid which is converted to a whole new amino acid ❖ Alpha-ketoglutarate (TCA cycle intermediate, product of step 3 in TCA cycle) ❖ Purpose it to remove the amino group format the amino acid ❖ Occurs in cytosol in cells ❖ Reversible
- Step 2: oxidative deamination ❖ Purpose is to recycle glutamate in order to regenerate alpha- ❖ Result: amino group of an amino acid has been converted to ammonium ion
- Urea cycle ❖ Purpose is to convert toxic NH4 (which converts to equally tocis ammonia) into non toxic urea that can be transport to kiddenu and excreted from body ❖ Combines the CO2 from TCA cly with NH4 to make urea in a four step cyclic metabolic pathway
