unit 3: cellular energetics

1st law of thermodynamics

energy cannot be created or destroyed

2nd law of thermodynamics

entropy of an isolated system can never decrease; the universe moves toward more disorder

entropy (S)

measure of disorder

metabolism

chemical processes within an organism that sustain life

anabolism

builds up; endergonic; non-spontaneous; ∆G > 0

catabolism

breaks down; exergonic reaction; spontaneous; ∆G < 0

gibs free energy (∆G)

measure of spontaneity of a reaction

spontaneous reaction

happens without any outside energy

∆G (equation)

∆H-T∆S

H

enthalpy; heat of a reaction

T

temperature

endothermic reaction

absorbs heat; +∆H

exothermic reaction

releases heat; -∆H

∆G ATP Hydrolysis

-7.3kcal/mol

ATP coupled reaction

combining a non-spontaneous reaction with ATP hydrolysis can make the reaction spontaneous

rate of a reaction (factors)

higher reactant concentration; higher surface-area of reactants; higher temperatures; free catalysts

biological catalysts

increases the rate of reaction by lowering the activation energy (Ea); not changed / used up by reaction

common exergonic reactions

hydrolysis of ATP; cellular respiration

common endergonic reactions

phosphorylation of ADP; photosynthesis

enzyme

biological catalyst; made of protein; -ase

substrate

reactants in a reaction

active site

where substrate attaches to enzyme

lock and key model

outdated; substrate fits perfectly into the active side

induced fit model

active site undergoes conformational change as substrate binds

coenzyme

non-protein organic compounds required for enzyme activity; part of active site; ex: vitamins

cofactor

non-protein inorganic compounds required for enzyme activity; ex: minerals

apoenzyme

protein part of enzyme

holoenzyme

whole enzyme; non-protein and protein

enzyme temperature

operate at optimum ____; can differ within species

enzyme pH

operate at optimum _; can differ within organism

denatured proteins

disrupted secondary/tertiary/quaternary structure; too far out of optimal condition; often irreversible

peptide bonds

not broken in denatured proteins

protein folding

not repeatable: order out of ribosome, golgi apparatus modifications, + protein chaperones

competitive inhibitor

bind to active site; stop substrate directly/slowly

noncompetitive inhibitor

bind to allosteric site; stop substrate indirectly/quickly

allosteric activator

bind to allosteric site; activates enzyme

allosteric inhibitor

bind to allosteric site; alters enzyme

photosynthesis

produce sugars from light energy; used by autotrophs

chemosynthesis

produce sugars from chemical energy; used by autotrophs

cellular respiration

produce ATP from sugar and oxygen; used by autotrophs and heterotrophs

fermentation

produce ATP from sugar without oxygen; used by autotrophs and heterotrophs

cyanobacteria

possible ancestor of chloroplast

chloroplast

outer membrane → intermembrane space → intermembrane → stroma → granum → thylakoid membrane → thylakoid → lumen

granum

stack of thylakoids

lumen

inside of thylakoid

chlorophyll

releases high energy electron when hit by light; needs to be reset

light reactions (location)

occurs in thylakoid membrane

calvin cycle (location)

occurs in stroma

light reactions (components)

electron transport chain; atp synthase

light reactions (reactants)

H₂O; NADP+; ADP

calvin cycle (reactants)

CO₂; NADPH; ATP

light reactions (products)

O₂; NADPH; ATP

calvin cycle (products)

C₆H₁₂O₆ (glucose); NADP+; ADP

in 2 turns

electron transport chain (photosynthesis)

PSII → cytochrome b → PSI; H₂O → O₂ & H+ + e-; NADP+ → NADPH

photosystem ii

reset by low energy e- from H₂O; energizes e- with light; passes e- to cytochrome b; contains chlorophyll

cytochrome b

hydrogen pump; energy from PSII e-; passes low energy e- to PSI

photosystem i

reset by e- from cytochrome/PSII; energizes e- with light; turns NADP+ + e- + H+ → NADPH; contains chlorophyll

atp synthase

synthesizes ATP; H+ concentration gradient spins; ADP → ATP

calvin cycle (components)

carbon fixation; reduction; regeneration

carbon fixation

rubisco brings in CO₂

reduction

ATP and NADPH used to create 6 G3P

regeneration

5 out of 6 G3P recycled in cycle

glycerol 3 phosphate (G3P)

2 used to make 1 glucose

photorespiration

calvin cycle rubisco takes in O₂; requires energy to fix

photorespiration (cause)

worsened by high O₂ concentrations (light reactions) + low CO₂ concentrations (calvin cycle)

stomata

structures under leaf; gate for gas exchange; usually closed at night to prevent water loss

c3 plants

standard photosynthesis; most efficient

c4 plant (what)

separation mitigates photorespiration; more energy intensive

cam plant (what)

high CO₂ mitigates photorespiration; more energy intensive

c4 plant (how)

light reaction in mesophyll cell (more O₂); calvin in bundle-sheath cell (less O₂)

cam plant (how)

stomata gathers CO₂ at night; CO₂ stored as malic acid in vacuole; malic acid converted to CO₂ at daylight

c3 plant (environment)

excels in wet environment; stomata rarely closes during day

c4 plant (environment)

excels in dry environment; stomata often closes during day

cam plant (environment)

excels in very dry environment; stomata closed during day

ventilation

physical movement of gasses into and out of the lungs

respiration

movement of gasses across a membrane

cellular respiration

creating ATP from C₆H₁₂O₆ (glucose) and oxygen

aerobic respiration

uses oxygen; ex: cellular respiration

anaerobic respiration

does not use oxygen; ex: fermentation

mitochondria

outer membrane → intermembrane space (acidic) → inner membrane → cristae → matrix

glycolysis (definition)

starting point of anaerobic and aerobic respiration; anaerobic

glycolysis (reactants)

C₆H₁₂O₆ (glucose); NAD+

glycolysis (products)

2 pyruvate; NADH; 2 ATP

glycolysis (location)

occurs within cytoplasm

krebs cycle (definition)

oxidization of pyruvate; aerobic

kreb cycle (reactants)

1 pyruvate

krebs cycle (products)

2 CO₂; 3 NADH; 1 FADH₂; 1 ATP; H+

pyruvate dehydrogenation

pyruvate + coenzyme a → acetyl-co a + CO₂ + NADH + H+

krebs cycle (location)

occurs within matrix

oxidative phosphorylation (definition)

cellular respiration; electron transport chain + ATP synthase; powered by krebs cycle

oxidative phosphorylation (reactants)

NADH; FADH₂

oxidative phosphorylation (products)

32-34 ATP; H₂O; NAD+; FAD; H+

oxidative phosphorylation (location)

occurs within intermembrane

complex i

reset by e- from NADH; pump H+ into intermembrane space; passes on e- to complex iii

complex ii

reset by e- from FADH₂; passes on e- to complex iii

complex iii

reset by e- from complex i and complex ii; pump H+ into intermembrane space; passes on e- to complex iv

complex iv

reset by e- from complex iii; pump H+ into intermembrane space; passes on e- to O₂ (creating H2O); 2H+ + ½O₂ + 2e- → H₂O

electron transport chain (cellular respiration)

complex i; NADH → complex ii; FADH₂ → complex iii → complex iv; O₂ → H₂O

carbs (to ATP)

sugar → glucose → glycolysis

fats (to ATP)

fatty acids → acetyl-co a

glycerol → glycolysis