AP Biology II | Unit 3 | Topics 3.4, 3.5 (finished)

Energy Coupling

energy released by an exergonic process powers an endergonic process

Examples of Energy Coupling

Glycolysis and Oxidative Phosphorylation

Energy Decoupling

energy from the proton gradient is released as heat instead of being used to make ATP; provides proteins and alternate way to return to the mitochondrial matrix without passing through ATP synthase again

Cellular Respiration Regulation

1) hormonal control of glucose entry

2) enzyme reversibility

3) enzyme sensibility to pH changes

4) feedback controls

Hormonal Control of Glucose Entry

Insulin increases glucose uptake in skeletal muscle and fat cells. This helps determine how much glucose is available for cellular respiration.

Enzyme Reversibility

Some reactions proceed in either direction, depending on the amounts of reactants and products. Other reactions strongly favor one direction under cellular conditions. These essentially irreversible steps often serve as control points, where regulation of an enzyme can speed up or slow down a pathway

Enzyme Sensibility to pH Changes

Changes in pH can alter an enzyme's shape and activity. During intense exercise, muscle pH may decrease, which can inhibit enzymes involved in glucose breakdown

Feedback Controls

The cell's energy status regulates key enzymes. High ATP signals that energy is plentiful, slowing glucose breakdown. High ADP signals that energy is needed, stimulating glucose breakdown

Fermentation

Process by which cells release energy in the absence of oxygen; when O2 is lacking, fermentation regenerates NAD+, otherwise, glycolysis would halt

Lactic Acid Fermentation

A series of anaerobic chemical reactions using pyruvic acid that supplies energy when oxygen is scarce; occurs in muscle cells when O2 is limited, mammalian red blood cells, & some bacteria

Alcohol Fermentation

Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide

Autotrophs

Organisms that make their own food

Photoautotrophs

use sunlight to make food; include plants, algae, and cyanobacteria

Chemoautotrophs

capture energy from inorganic compounds to make food

Hetertrophs

Organisms that depend on other organisms for their food; rely on the sugars produced by autotrophs for their energy needs

Photosynthesis

Conversion of light energy from the sun into chemical energy.

Photosynthetic Reactants

*H2O is absorbed by the roots from the soil

*CO2 is acquired from the air as a result of gas exchange through the stomata (small pores on the leaf underside)

*Likewise, the O2 waste product exits through the stomata.

*Sunlight

Mesophyll

the middle of a leaf, chloroplasts are mainly found in these cells of leaf

Stomata

pores in leaf where CO2 enters and O2 exits

Thylakoid

flat green pancakes; they stores chlorophyll and collect sun energy for the first part of photosynthesis

Grana

stacks of thylakoid; increases surface area

Stroma

the fluid that surrounds the thylakoids; the site where the second half of photosynthesis occurs; contains ribosomes and chloroplast DNA

Light Reaction

the first stage of photosynthesis during which energy from light is used for the production of ATP

Inputs of Light Reaction

Light, H2O, NADP+, ADP

Outputs of Light Reaction

O2, ATP, NADPH

Location of Light Reaction

thylakoid membrane

Calvin Cycle

reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars

Inputs of Calvin Cycle

CO2, ATP, NADPH

Outputs of Calvin Cycle

ADP, NADP+, G3P

Location of Calvin Cycle

stroma of the chloroplast

Light Energy

electromagnetic energy that behaves as waves and is absorbed or emitted in discrete units called photons

Electron Transport Chain, PSII to PSI

Electrons travel through plastoquinone (Pq) → cytochrome complex → plastocyanin (Pc). Energy released during electron transport helps build an H⁺ gradient, with more H⁺ in the thylakoid lumen.

Electron Transport Chain, PSI to NADPH

Light reenergizes the electrons in PSI. They pass to ferredoxin (Fd) and then to NADP⁺ reductase, which transfers them to NADP⁺.

NADP⁺ is the final electron acceptor, accepting two electrons and an H⁺ to form NADPH.

Three Stages of the Calvin Cycle

carbon fixation, reduction, regeneration

ETC in Photosynthesis vs. Cellular Respiration (Similarities)

*Both use excited electrons to power active transport of H+

*Both create proton gradient to power ATP Synthase

ETC in Photosynthesis vs. Cellular Respiration (Differences)

*Source of excited electrons: light photon vs NADH (electron carrier)

*Products: ATP & NADPH in Photosynthesis vs NAD+,FAD,H20, & ATP in cell respiration