Bio 101 Unit 2

Energy

ability to do work/move matter

Kinetic energy

energy of motion (sound, light, contracting muscles)

Potential energy

stored available energy (energy bar, chemical bonds, chemical gradient)

Thermal energy

energy from heat and light

chemical energy

energy stored in chemical bonds

first law of thermodynamics

energy is never created nor destroyed

second law of thermodynamics

entropy of the universe is always increasing over time since heat is lost at each step of the energy cycle

entropy

amount of disorder or randomness of heat energy

• entropy in universe increases when molecules are formed (dehydration synthesis)

Chemical reactions

rearrange atoms - energy is either put in or released

Endergonic

rxn that requires energy to forms bonds

• dehydration synthesis (joining molecules)

• reduction

• powered by ATP

exergonic

rxn that releases energy when breaking bonds

• hydrolysis

• oxidation

• power ATP synthase

energy coupling

energy produced by one rxn is used to drive another rxn

oxidation-reduction rxn

most energy transformations in organisms where electrons are transferred from donor to acceptor

Oxidation

atom/molecule donates electron releasing energy that was stored in electrons (exergonic)

reduction

gain of electrons by atom/molecule which gains energy from released electrons (endergonic)

electron transport chain

series of membrane proteins performing sequential/linked oxidation/reduction rxns

• used in photosynthesis and cellular respiration

• released energy is stored in cells to use in other rxns

ATP

nucleotide that temporarily stores energy to power chemical rxns

• removing end phosphate grp via hydrolysis releases potential energy

• formed during cellular respiration - release energy from sugar (ADP → ATP)

• ATP breakdown is coupled - ATP breakdown powers endergonic rxns

Enzymes

protein that acts as a catalyst - speeds up chemical rxn and lower energy required

• substrate binds to active site on enzyme where rxn occurs and releases product

• some enzymes combine two substrates

• activation energy - amt required to start rnx

• hv optimal temperature, salt concentration and pH

Cofactors

bind to enzyme to help catalyze - increase enzyme activity

Enzyme inhibitors

used to prevent unneeded rxns from occurring

• noncompetitive: binds to separate spot on enzyme to change active site shape so it cannot bind to substrate anymore

• competitive: binds to enzyme in place of substrate (may be product of rxn binding to enzyme when numbers increase)

feedback loops

• negative feedback - once enough final product is produced, this product can bind to initial enzyme as inhibitor

• positive feedback - final product binds to initial enzyme to speed up production (acts as its own cofactor)

selective permeability

solutes enter/exit cells depending on concentration gradient (high → low), polarity, charge and size

Passive transport

down the concentration gradient

• simple diffusion - small nonpolar molecules move across membrane (O2 moves from lungs to red blood cells)

• osmosis - diffusion of water accross membrane for equal solute ratio in/out of cell

• facilitated diffusion - membrane proteins transport ions and polar substances (hydrogen ions using transport proteins produce ATP) (glucose from food moves into cells)

Tonocity

ability of extracellular solution to make water move in/out of cell

• hypotonic: water moves into cell - higher solute concentration inside cell

• hypertonic: water moves out of cell - higher solute concentration outside cell

• isotonic: water does not move - equal concentration in/out of cell

Water balance in plants

plants keep solute higher inside cells to get water to enter cell to maintain turgor pressure. (hypertonic = loss of water = vacuole shrinks = plants wilt

Active Transport

uses ATP to transport against concentration gradient (ions moved in/out neurons/muscle cells)

• protein pump - sodium-potassium pump moves 3 Na+ out of cell and 2 K+ into cell

• endocytosis: vesicles engulf large molecules into cell

• exocytosis: vesicles to secrete large polar molecules (proteins - mammary/milk) out of cell

• pinocytosis: cell takes in fluid via vessicles

• Phagocytosis: cell releases water via vessicles

Photosynthesis

converting light (kinetic) energy into chemical (potential) energy

• 6CO2 + 6H2O + light → C6H12O6 (sugar) + 6O2

• conducted by autotrophs (cyanobacteria in water, doesn’t include kingdom archaea)

electromagnetic spectrum

• wavelength: short wavelength = high energy

• visible light: wavelength that appear as color

• photons: packets of light energy - captured by photosynthesizers in pigment

Pigment

molecules that capture energy from light

• chlorophyll a: blue-green (most pop)

• chlorophyll b: yellow - green

• carotenoids: red, orange, yellow

Plant structure

• stomata: leaf pores where gas exchange occurs - contains mesophyll cells: sole purpose is photosynthesis

• stroma: fluid inside chloroplasts

• thylakoids: coin like membranes inside stroma

• granum: stack of thylakoids

• inner membrane + outmembrane + intermembrane space btwn both

• chrorophyll: photosynthetic pigment

Light reactions

1) light strikes Photosystem II (protein in thylakoid membrane) where chlorophyll absorbs light and transfers to e- from H2O

2) e- moves to ETC and heads to Photosystem I where chlorophyll transfers energy to e-

3) e- moves to seconds ETC

(produces NADPH and ATP which power later carbon rxns)

Carbon reactions

Calvin cycle: occurs in stroma

1) rubisco enzyme catalyzes first rxn

2) carbon fixation: rubisco adds CO2 onto RuBP forming unstable 6 carbon org mol

3) PGAL synthesis: uses ATP+NADPH energy to convert PGA into PGAL → multiple PGALS (one from each cycle) combine to form glucose molecules)

4) RuBP regeneration: some PGAL is used to reform RuBP (5 carbon) which restarts new cycle

• Photorespiration: occurs due to O2 buildup inside leaf to release it - decreases rate of photosynthesis

• C3, C4, CAM plants use different pathway for carbon fixation

aerobic cellular respiration

• C6H12O6 + O2 → CO2 + H2O + ATP

• 1 glucose produces 36 ATP

• glycolysis, krebs (calvin) cycle, ETC

glycolysis

• occurs in cytosol in all cells

• 1 glucose + 2ATP → 2 3C pyruvate (PGAL) → oxidation = 2 NADH → substrate level phosphorylation = 2 ATP each (x2 = 4 total ATP)

• overall: 1 glucose, 2 NAD+, 2 ADP → 2 pyruvate, 2 NADH, 2 ATP

• transition step: 2 pyruvate → 2 acetyl CoA, releases CO2 & NAD+ → NADH

• probably first of 3 pathways to emerge

Krebs Cycle

• occurs in: prokaryotes - cytosol, eukaryotes - mitochondria

• 2 acetyl CoA oxidized → energy transfer to e- → release 4 CO2, 2 ATP, 6 NADH, 2 FADH2

Electron Transport Chain

• occurs in: prokaryotes - cytosol, eukaryotes - mitochondria

• e- potential energy used

• NADH + FADH2 donate e-s to ETC → H+ gradient formed from e- transporting H+ into intermembrane space and into matrix into ATP synthase enzyme (chemiosmotic phosphorylation) → yeilds 34 ATP

• extra e- donated to O2 which then bonds with H+ to form H2O

Anaerobic respiration

• occurs in many prokaryotes

• different e- acceptors than O2 (nitrate, sulfate, CO2)

• less ATP production

• includes fermentation

Fermentation

only glucose - continues cycles to produce 2 ATP per cycle

• pyruvate oxidizes NADH → NAD+

• pyruvate can be converted into alcohol or lactic acid

• Alcoholic fermentation: NADH reduces pyruvate to ethanol creating NAD+ (carried out by microbes)

• lactic acid fermentation: NADH reduces pyruvate to lactic acid creating NAD+ (occurs in bacteria + muscle cells)