mastering biology chapters 6 & 7

cellular respiration

cellular respiration

• C6H12O6 + 6O2 → 6H2O + 6CO2 + ATP

• Exergonic process in which 34% of the energy in glucose is captured in ATP

  • Glucose oxidizes to CO2 by losing H+

  • Oxygen reduces to H2O by gaining H+

• O2 is consumed as organic molecules are broken down to CO2 & H2O

ATP

• Main energy source for cells

• Releases energy when its phosphate bonds are hydrolyzed

• Contains 2 phosphoanhydride (high-energy) bonds

respiration

• Exchange of gases

redox reaction (oxidation-reduction reaction)

• Transfer of electrons from one molecule to another

• In cellular respiration, electrons are transferred from organic fuels (glucose) to oxygen, releasing energy

oxidation

• Loss of electrons from a substance

• In cellular respiration, glucose is oxidized to CO2 as it loses H+

reduction

• Gain of electrons by a substance

• In cellular respiration, O2 is reduced to H2O as it gains H+

NAD+

• Organic molecule used to shuttle electrons in redox reactions

• Reduced to NADH after it accepts 2 electrons

glycolysis

• Glucose is oxidized into 2 molecules of pyruvate, using 2 ATP

• 2 molecules of NAD+ are reduced to 2 NADH, producing 4 ATP (net gain of 2 ATP)

• Occurs in the cytoplasm, not requiring any oxygen

substrate-level phosphorylation

Formation of ATP by an enzyme directly transferring a phosphate group from a substrate (organic molecule) to ADP

intermediate

• Compound that forms between the initial reactant & the final product in a metabolic pathway

pyruvate oxidation

• Carboxyl group is removed from pyruvate, releasing CO2

• Remaining 2C molecule is oxidized, reducing NAD+ to NADH

• Oxidized 2C molecule (acetyl group) is attached to CoA, forming acetyl CoA

• Occurs in the mitochondrial matrix

acetyl CoA

• Entry compound for the citric acid cycle

• Formed from a 2C fragment of pyruvate attached to a coenzyme

citric acid cycle

• Acetyl CoA is attached to a 4C oxaloacetate to form 6C citrate, releasing the CoA group

• Oxidation of isocitrate & a-ketoglutarate releases CO2 & reduces NAD+ to NADH

• 3 ATP are formed after 3P are transferred to 3 ADP

• Oxidation of succinate reduces FAD to FADH2

• Oxaloacetate is regenerated by the oxidation of malate, reducing NAD+ to NADH

oxidative phosphorylation

• Involves the electron transport chain (ETC) & chemiosmosis

• Nearly 90% of the ATP generated is made in this stage

electron transport chain (ETC)

• Series of electron carrier molecules that shuttle electrons during redox reactions, releasing energy used to make an electrochemical gradient

  • NADH & FADH2 shuttle electrons to the ETC, regenerating into NAD+ & FAD+

  • Electron carriers pass electrons down the staircase to O, the final electron acceptor, forming H2O as it takes up H+

• Most of the ATP produced by cellular respiration is generated by this process

• Located in the inner membrane of the mitochondria

chemiosmosis

• Uses the energy released from the ETC to pump H+ into the intermembrane space

  • H+ flows through ATP synthase back into the matrix, harnessing the flow to synthesize ATP

• Powers most ATP synthesis in cells

  • Energy of the H+ concentration gradient is used to make roughly 28 ATP by oxidative phosphorylation

ATP synthase

• Enzyme that functions in chemiosmosis with adjacent ETC’s

  • Uses the energy of the H+ concentration gradient to synthesize ATP

fermentation

• Anaerobic harvesting of energy from glucose

• Nets 2 ATP by taking advantage of glycolysis

• Provides an anaerobic path for oxidizing NADH to NAD+

lactic acid fermentation

• Glycolysis followed by the reduction of pyruvate into lactate

• Regenerates NAD+ for glycolysis

• Muscle cells can switch to lactic acid fermentation when the need for ATP exceeds the delivery of O2

• Used to make cheese & yogurt by bacteria

alcohol fermentation

• Glycolysis followed by the reduction of a derivative of pyruvate into ethanol

• Regenerates NAD+ & releases CO2

• Used by yeast cells to produce ethanol in alcoholic drinks

obligate anaerobe

• Organisms that are poisoned by oxygen, requiring anaerobic conditions

  • I.e. stagnant ponds, deep soils

facultative anaerobe

• Organisms not poisoned by oxygen

  • I.e. yeast & bacteria

• Can switch between aerobic respiration & anaerobic pathways

biosynthesis

• Production of organic molecules using energy-requiring metabolic pathways

• Amino acids, lipids, & other carbohydrates can be converted into intermediates of glycolysis & citric acid cycle

photosynthesis

• 6CO2 + 6H2O → C6H12O6 + 6O2

• Process in which solar energy is used to convert CO2 & H2O into glucose & O2

• Occurs in the chloroplast of plants & algae & some protists & prokaryotes

• CO2 becomes reduced to glucose after H2O is oxidized

  • Electrons are transferred along with H+

light reactions

• Process by which solar energy is absorbed & converted into the chemical energy of ATP & NADPH

• H2O is converted into O2

• Forms an electrochemical gradient to synthesize ATP

• Occurs in the thylakoids

NADP+

• Electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions

  • Provides electrons for reducing C compounds in the Calvin cycle

Calvin cycle

• In carbon fixation, rubisco combines 3CO2 with 3RuBP to form 6 3-PGA

• P from 6 ATP & electrons from 6 NADPH reduce the 6 3-PGA into 6 G3P

• 1 G3P exits the cycle & can be used to make glucose for a net gain of 1 G3P for every 3 CO2

• During regeneration, 3 ATP are used to rearrange the remaining 5 G3P (15 C’s) into 3 RuBP (15 C’s)

• Occurs in the stroma

carbon fixation

• Incorporation of C from atmospheric CO2 into an organic compound

• C that is fixed into sugar during photosynthesis can be used to build other organic molecules

• C is fixed into a 3C sugar as it enters the Calvin cycle in C3 plants

• C is fixed into a 4C sugar as it enters the Calvin cycle in C4 & CAM plants

C3 plant

Plant that uses the Calvin cycle to fix CO2 into an organic 3C compound as the first stable intermediate (3-PGA)

C4 plant

Plant that uses reactions to fix CO2 into a 4C compound (oxaloacetate), providing CO2 for the Calvin cycle

CAM plant

• Plant that uses a photosynthetic adaptation in arid conditions

• CO2 enters open stomata in the night, converting it into oxaloacetate

• Releases CO2 for the Calvin Cycle during the day, where the stomata are closed

chloroplast

• Uses solar energy to convert CO2 & H2O into glucose & O2

carotenoid

• Yellow & orange pigments located in the chloroplast

• Shows through once the green chlorophyll breaks down

• Can absorb & dissipate light energy, preventing damage to chlorophyll & the interaction with O to form damaging oxidative molecules

photosystem

• Light-capturing protein & pigment complex of a thylakoid membrane

• Consists of a reaction-center complex surrounded by light-harvesting complexes

photosystem II

• Pigment molecules absorb light energy, passing it to the reaction center complex

• Primary electron acceptor captures electrons from chlorophyll a when boosted to a higher energy state

• H2O is split to replace the captured electron

  • Electrons are donated to photosystem II, with the remaining O & H ions released into the thylakoid

• Released energy pumps H+ into the thylakoid space, driving chemiosmosis

photosystem I

• Pigment molecules absorb light energy, passing it to the reaction center complex

• Primary electron acceptor captures electrons from chlorophyll a when boosted to a higher energy state

• Electrons that flow down the ETC from PSII replace the captured electron

• Captured electron is passed through a short ETC, reducing NADP+ to NADPH at the end of the chain

  • NADPH provides some energy to fuel the Calvin cycle

chlorophyll

Green pigment located within the chloroplasts or in the membranes of certain organisms

chlorophyll a

• Participates directly in light reactions, converting solar energy into chemical energy

• Absorbs mainly blue-violet & red light

chlorophyll b

• Absorbs blue & orange light

• Broadens the range of light a plant can use by conveying absorbed energy to chlorophyll a, which uses it in the light reactions

mesophyll

• Leaf cells specialized for photosynthesis

• A leaf’s ground tissue system

stomata

• Pores surrounded by guard cells in the lower epidermis of a leaf

  • When open, CO2 enters a leaf, H2O & O2 exit into the mesophyll layer

• Plants conserve H2O when its stomata are closed

stroma

• Fluid in the chloroplast that surrounds the thylakoid membrane

• Sugars are made here by the enzymes of the Calvin cycle

thylakoid

• Flattened membranous sac inside a chloroplast

• Membranes contain chlorophyll & the light reaction complexes

pigment

• Light-absorbing molecules built into the thylakoid membranes that absorb or reflect certain wavelengths of light

granum

• Stack of thylakoids

photophosphorylation

Production of ATP by chemiosmosis during the light reactions of photosynthesis

photorespiration

• Metabolic pathway that consumes O2, releases CO2, & decreases photosynthetic output

• Usually occurs on hot, dry days

• Stomata close, O2 accumulates, rubisco fixes O2 instead of CO2

• Produces no sugar molecules or ATP

wavelength

Distance between crests of adjacent waves

electromagnetic spectrum

Entire spectrum of electromagnetic radiation ranging in wavelength

photon

• Fixed quantity of light energy

• The shorter the wavelength of light, the greater the energy of a photon

autotroph

• Organism that makes its own food

photoautotroph

• Organism that obtains energy from sunlight to convert CO2 into organic molecules

heterotroph

• Organism that obtains organic food molecules by consuming other organisms

• Consumer or decomposer in a food chain

kilocalorie (kcal)

• Quantity of heat equal to 1,000 calories

• Called a “calorie” when measuring the energy content of food

greenhouse effect

Warming of Earth due to the atmospheric accumulation of CO2 & other gases, absorbing infrared radiation & reradiating some it back towards Earth

climate change

Increase in temperature & change in weather patterns around the planet due to the burning of fossil fuels