mastering biology chapters 6 & 7

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

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* 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

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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

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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