Cellular Energy: Photosynthesis and Respiration

Vocabulary flashcards covering cellular energy, ATP structure and function, photosynthesis reactions, cellular respiration stages, and fermentation pathways.

Chemical energy

Energy stored in the bonds of chemical compounds, which allows energy to be transported around the cell.

Adenosine triphosphate (ATP)

The energy currency for cells composed of adenine, ribose, and 3 phosphate groups, which stores and transports energy for biological work.

ATP-ADP cycle

The process where breaking the bond between the 2nd and 3rd phosphate groups releases energy to form ADP and $P_i$, while bonding them back together stores energy.

Autotrophs

Organisms that can make their own food from sunlight through photosynthesis.

Heterotrophs

Organisms that need to consume other organisms for food.

Chlorophyll

A pigment found in chloroplasts that absorbs blue/violet and red light, reflects green and yellow light, and energizes electrons when absorbing light energy.

Chloroplasts

Two-membrane organelles containing sac-like thylakoids and stroma where photosynthesis reactions occur.

Thylakoid

Sac-like membrane structures inside chloroplasts arranged in stacks called grana, where light-dependent reactions take place.

Stroma

The fluid-filled space surrounding thylakoid stacks inside a chloroplast, where light-independent reactions take place.

Granum

A stack of thylakoids inside a chloroplast.

NADP+

An electron transport molecule that accepts and carries high-energy electrons between light-dependent and light-independent reactions.

Light-dependent reactions

Photosynthesis reactions occurring in the thylakoids that require light and water to produce oxygen, ATP, and NADPH.

Light-independent reactions

Photosynthesis reactions occurring in the stroma (also called the Calvin Cycle) that use $CO_2$, ATP, and NADPH to produce glucose without requiring sunlight.

Photosystems

Combinations of chlorophyll pigments and specialized proteins in the thylakoids that collect sunlight to energize electrons.

Photolysis

The process of breaking apart $H_2O$ molecules ($2H_2O \rightarrow 4H^+ + 4e^- + O_2$) in light-dependent reactions to replace electrons in the Electron Transport Chain.

Photosynthesis equation

The chemical equation $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$, representing carbon dioxide and water reacting in the presence of light and chlorophyll to yield glucose and oxygen.

Cellular respiration

The process by which all organisms break down glucose to gradually produce energy in the form of ATP.

Cellular respiration equation

The chemical equation $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (ATP)}$.

Aerobic respiration

Respiration that occurs when oxygen is available, consisting of glycolysis, the Krebs Cycle, and the Electron Transport Chain, yielding about 36 ATP.

Anaerobic respiration

Respiration that occurs when oxygen is not available, consisting of glycolysis followed by fermentation, yielding 2 ATP.

Glycolysis

The initial step of cellular respiration occurring in the cytoplasm, breaking a glucose molecule into 2 pyruvic acid molecules, producing 2 ATP and passing electrons to $NAD^+$.

Krebs Cycle

The step of cellular respiration occurring in the mitochondria where pyruvic acid breaks down, releasing $CO_2$, ATP, and high-energy electrons carried on FAD and $NAD^+$.

Electron Transport Chain

A series of molecules in the mitochondria where high-energy electrons move $H^+$ ions across the membrane, powering ATP synthase to generate ATP while forming $H_2O$.

ATP synthase

An enzyme turned by returning $H^+$ ions moving back across the mitochondrial membrane to generate large amounts of ATP.

Fermentation

An anaerobic process following glycolysis that recycles $NADH$ back to $NAD^+$ so glycolysis can continue producing ATP when oxygen is absent.

Alcoholic fermentation

A type of fermentation carried out by yeast that produces ethyl alcohol and $CO_2$, used in bread baking and beverage production.

Lactic acid fermentation

A type of fermentation that produces lactic acid, used in human muscles for quick energy and by bacteria to make kimchi, pickles, sauerkraut, yogurt, and sour cream.