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68 Cards in this Set
- Front
- Back
Structural Proteins
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Made from long polymers
Maintain and add strength to cellular and matrix structure (collagen, globular tubulin) |
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Glycoproteins
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Proteins with carbohydrate groups attached
Components of cellular plasma membranes |
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Proteoglycans
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Mixture of proteins and carbohydrates
Consist of more than 50% carbohydrates Major component of extracellular matrix |
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Cytochromes
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Proteins which require a prosthetic (nonproteinaceous) heme group in order to function
Add color to cell Examples: Hemoglobin Cytochromes of electron transport chain in inner-membrane of mitochondria |
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Conjugated Proteins
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Proteins containing nonproteinaceous components
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Carbohydrates
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Sugars or saccharides
Made from carbon and water Empirical formula = C(H2O) |
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Glucose
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6-C carbohydrate
Most commonly occurring Account for 80% of carbohydrates absorbed by humans All digested carbohydrates reach cells as glucose Forms ring over chain form in aqueous solutions |
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Glucose anomers
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Ring form
Alpha-glucose: hydroxyl group on anomeric C (C #1) and methoxy group (C #6) are on opposite sides of ring Beta-glucose: hydroxyl group and methoxy group are on same side of ring |
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Glycogen
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Glucose is oxidized to form ATP
If sufficient ATP, glucose is polymerized to a polysaccharide (glycogen) or converted to fat Found in all animal cells, large amounts in liver and muscle cells |
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Starch
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2 forms:
1. Amylose (isomer of cellulose, same alpha linkages as glycogen) 2. Amylopectin (resembles glycogen, different branching structure) Plants make starch from glucose |
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Cellulose
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Contains beta-linkages
Plants form cellulose from glucose Animals do not have enzymes to digest beta-linkages (bacteria inside animals do) |
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3 components of Nucleotides
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1. 5-C sugar
2. Nitrogenous base 3. Phosphate group |
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5 common nitrogenous bases in nucleotides:
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1. Adenine (A)
2. Guanine (G) 3. Cytosine (C) 4. Thymine (T) 5. Uracil (U - replaces T in RNA) A & T form 2 H-bonds C &G form 3 H-bonds |
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Nucleotides form:
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Polymers to create:
1. Nucleic acids 2. DNA (double stranded) 3. RNA (single stranded) Written 5' to 3' |
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Phosphodiester bonds
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In nucleic acids, nucleotides join together by phosphodiester bonds between phosphate group and 1 nucleotide and 3rd C of pentose of other nucleotide
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Double helix
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In DNA, 2 strands are joined by hydrogen bonds to make this structure
Top strand runs 5' - 3' Bottom strand runs 3' - 5' |
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Adenosine Triphosphate (ATP)
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Nucleotide
Source of readily available energy for the cell |
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Cyclic AMP
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Component in many second messenger systems
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NADH & FADH2
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Coenzymes involved in Krebs cycle
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Minerals
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Dissolved inorganic ions inside and outside cell
By creating electrochemical gradients across membranes, they assist in transport of substances entering and exiting cells Can combine and solidify to give strength to a matrix (hydroxyapatite in bone) Act as cofactors assisting enzyme or protein function (iron in heme, prosthetic group of cytochromes) |
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Enzymes
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Globular proteins
Act as a catalyst = lowering activation energy for biological reactions and increasing reaction rates Not consumed or permanently altered by reactions Do not alter equilibrium of reaction |
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Substrate
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Reactant upon which an enzyme works
Smaller than enzymes |
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Active site
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Position on enzyme to which subtrate binds with numerous covalent bonds
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Enzyme-substrate complex
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Enzyme bound to substrate
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Enzyme specificity
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Enzymes are designed to work only on a specific substrate or group of closely related substrates
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Lock & Key Theory
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Example of enzyme specificity
Active site of enzyme has specific shape (lock) that only fits a specific substrate (key) Model does not explain all enzymes |
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Induced Fit Model
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Shape of both enzyme and substrate are altered upon binding
Alteration helps reaction proceed and increases specificity |
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Saturation Kinetics
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As relative concentration of substrate increases, rate of reaction also increases, but to a lesser degree until a maximum rate (Vmax) is achieved
More substrate is added and therefore wait in line for free enzyme Vmax is proportional to substrate concentration |
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What affects enzyme reactions?
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1. Substrate concentration
2. pH (optimal pH) 3. Temperature (as temperature increases, reaction rate increases until enzyme denatures) |
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Cofactor
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Non-protein component that helps enzymes reach their optimal activity
Can be coenzymes or metal ions |
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Coenzymes
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1. Cosubstrates
2. Prosthetic groups Organic molecules |
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Cosubstrates
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Category of cofactor
Reversibly bind to a specific enzyme and transfer some chemical group to another substrate Reverted to original form by another enzymatic reaction (distinguishing it from a normal substrate) Example: ATP |
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Prosthetic groups
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Remain covalently bound to enzyme throughout reaction
Emerge from reaction unchanged Example: Heme & metal ions (can act alone or with prosthetic group) |
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Vitamins
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Can be coenzymes
Are essential organic molecules: cannot be produced by body |
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Apoenzyme
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Enzyme without cofactor
Completely nonfunctional |
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Holoenzyme
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Enzyme with cofactor
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3 mechanisms of enzyme inhibition
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1. Irreversible inhibition
2. Competitive inhibition 3. Noncompetitive inhibition |
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Irreversible Inhibitors
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Agents which bind covalently to enzymes and disrupt their function
Highly toxic (penicillin) |
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Competitive Inhibitors
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Compete with substrate by binding reversibly with noncovalent bonds to active site
Can overcome inhibition by increasing concentration of substrate Resemble substrate |
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Noncompetitive Inhibitors
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Bind noncovalently to enzyme at spot other than active site and change conformation of enzyme
Do not prevent substrate from binding Bind to enzyme with substrate and enzyme without substrate Do not resemble substrate Act on more than one enzyme Cannot be overcome by excess substrate Do not lower enzyme affinity for substrate |
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4 mechanisms by which enzymes are regulated:
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1. Proteolytic cleavage (irreversible covalent modification)
2. Reversible covalent modification 3. Control proteins (activate or inhibit activity) 4. Allosteric interactions (modification of enzyme) |
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Zymogen (proenzyme)
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Inactive form of enzyme
Specific cleavage of peptide bonds, irreversibly activates enzyme Activation may be instigated by other enzymes Example: pepsinogen (pepsin) |
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Allosteric Interactions
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Modification of enzyme conformation resulting from binding of activator or inhibitor at specific binding site on enzyme
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Negative feedback (feedback inhibition)
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Product of downstream reaction inhibits enzymatic activity in upstream reaction
Provides shut-down mechanism for series of enzymatic reactions when it has produced sufficient amount of product Do not resemble substrate of enzymes that they inhibit - bind to enzyme and cause conformational change (allosteric regulation) |
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Positive feedback
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Product activates enzyme
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Positive cooperativity
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1st substrate changes shape of enzyme allowing other substrates to bind more easily
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Negative cooperativity
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1st substrate changes shape of enzyme, inhibiting substrate binding
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Enzyme Nomenclature
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Suffix "ase" is added to end of substrate upon which enzyme acts
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Lyase
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Catalyzes addition of 1 substrate to a double bond of a 2nd substrate (synthase)
Example: ATP synthase |
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Ligase
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Governs an addition reaction (synthetase)
Requires energy from ATP or other nucleotide |
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Kinase
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Enzyme which phosphorylates something
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Phosphotase
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Enzyme which dephosphorylates something
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Metabolism
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Cellular chemical reactions
1. Anabolism (molecular degradation) 2. Catabolism (molecular synthesis) |
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3 Stages of Metabolism:
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1. Breakdown of macromolecules to constituent parts (no energy release)
2. Constituents are oxidized to acetyl CoA, pyruvate - forming ATP and reduced coenzymes (NADH & FADH2) in process which does not directly use O2 3. If O2 available (or can be used) metabolites go into citric acid cycle and oxidative phosphorylation to form large amount of energy - otherwise coenzyme NAD+ and other byproducts are recycled or expelled as waster |
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Respiration
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1st & 2nd stage - energy acquiring stages of metabolism
Glucose + O2 = CO2 + H2O (not balanced - combustion reaction) |
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Aerobic respiration
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Oxygen is used
Produces 36x net ATP (includes glycolysis) 1x NADH = 2-3x ATP 1x FADH2 = 2x ATP |
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Anaerobic respiration
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Oxygen is not required
1st stage: Glycolysis Fermentation |
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Glycolysis
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1st stage of aerobic and anaerobic respiration
Series of reactions that break 6-C glucose molecules into 2x 3-C molecules of pyruvate (conjugate of pyruvic acid) Produces: 1. 2x ATP from ADP 2. Inorganic phosphate 3. Water 4. 2x NADH from NAD+ reduction 5. 2x pyruvate molecules from glucose Operates in both presence and absence of oxygen Occurs in cytosol |
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Substrate level phosphorylation
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Formation of ATP from ADP and inorganic phosphate using the energy released from the decay of high energy phosphorylated compounds)
As opposed to using energy from diffusion |
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Fermentation
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Anaerobic respiration
1. Glycolysis 2. Reduction of pyruvate to ethanol or lactic acid (expelled with CO2 as waste product) 3. Oxidation of NADH back to NAD+ Yeast and microorganisms produce ethanol Humans produce lactic acid Takes place when: 1. Organism is unable to assimilate energy from NADH and pyruvate 2. Has no oxygen available |
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Matrix of Mitochondria
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Site where products of glycolysis (pyruvate and NADH) move to
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Inner mitochondrial membrane
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Less permeable than outer-membrane
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Acetyl CoA
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Once inside matrix, pyruvate is converted to acetyl CoA in a reaction that produces NADH & CO2
Coenzyme which transfers 2-C from pyruvate to 4-C oxaloacetic acid to begin Krebs cycle |
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Krebs Cycle (citric acid cycle)
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Each turn produces:
1. 1x ATP 2. 3x NADH 3. 1x FADH2 4. 2x C lost 5. Oxaloacetic acid regenerted to begin cycle again Process of ATP production is substrate-level phosphorylation 1x glucose = 2x turns of Krebs cycle |
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Electron Transport Chain (ETC)
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Series of proteins, including cytochromes with heme, in inner-membrane of mitochondria
1st protein complex oxidizes NADH by acceptin its high energy electrons Electrons are passed down protein series and ultimately accepted by oxygen to form water As electrons are passed along, protons are pumped intro intermembrane space for each NADH - establishes proton gradient which propels protons through ATP synthase to manufacture ATP (oxidative phosphorylation) 2-3x ATP made from each NADH 2x ATP made from FADH2 (reduces protein) |
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Proton-motive force
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Proton gradient established from pumping out of protons into intermembrane space, which propels protons through ATP synthse to make ATP
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ATP synthase
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Makes ATP by oxidative phosphorylation
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Intermembrane space
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Lower pH than matrix
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