Honors Biology Cell Energy FLASHCARDS

A set of flashcards covering key vocabulary and concepts in cell energy, photosynthesis, and respiration for Honors Biology.

Efficiency of aerobic respiration

Aerobic respiration yields significantly more ATP compared to anaerobic glycolysis.

Adenosine Triphosphate (ATP)

The main energy-carrying molecule used by cells to power chemical reactions.

Adenosine Diphosphate (ADP)

The lower-energy molecule that can be converted to ATP by adding a phosphate group.

Phosphorylation

The process of adding a phosphate group to a molecule, such as turning ADP into ATP.

Autotroph

An organism that makes its own food using energy from sunlight or chemicals.

Heterotroph

An organism that obtains energy by consuming other organisms.

Photosynthesis

The process by which plants, algae, and some bacteria convert light energy into chemical energy (glucose).

Wavelength

The distance between peaks of light waves; determines the color and energy of light.

Pigment

A light-absorbing molecule that gives color to plant tissues.

Chlorophyll

The main pigment in plants that absorbs light energy for photosynthesis.

Chloroplast

The organelle in plant cells where photosynthesis occurs.

Thylakoid

Disk-shaped membrane structures in chloroplasts that contain chlorophyll and are the site of light-dependent reactions.

Stroma

The fluid-filled space around the thylakoids in a chloroplast; site of the Calvin Cycle.

Stomata (stoma)

Small openings on the underside of leaves that allow gas exchange (CO₂ in, O₂ out).

Xylem

Plant tissue that transports water from roots to leaves.

Phloem

Plant tissue that transports sugars and nutrients throughout the plant.

Light-dependent reactions

The first stage of photosynthesis where light energy splits water, releasing oxygen and creating ATP and NADPH.

Photosystem I

Part of the light-dependent reactions that produces NADPH.

Photosystem II

Part of the light-dependent reactions that captures light to split water and release oxygen.

Electron Transport Chain (ETC)

A series of proteins that transfer electrons and help generate ATP.

ATP Synthase

An enzyme that uses hydrogen ion flow to convert ADP into ATP.

Calvin Cycle

The second stage of photosynthesis that uses CO₂, ATP, and NADPH to make glucose.

NADP⁺/NADPH

Electron carrier molecules that transport energy during photosynthesis.

Carbon Dioxide (CO₂)

A gas taken in by plants during photosynthesis to make glucose.

Glucose (C₆H₁₂O₆)

A simple sugar produced by photosynthesis; main source of energy for cells.

Anaerobic

A process that occurs without oxygen.

Fermentation

A form of anaerobic respiration that regenerates NAD⁺ to keep glycolysis going.

Glycolysis

The first step of cellular respiration; breaks glucose into pyruvate, making a small amount of ATP.

Pyruvic Acid (Pyruvate)

The product of glycolysis that enters the next stages of respiration.

NAD⁺/NADH

Electron carrier molecules that transport high-energy electrons during respiration.

Lactic Acid

Product of anaerobic respiration in animal cells; causes muscle fatigue.

Ethanol (Alcohol)

Product of fermentation in yeast and some bacteria.

Aerobic

A process that requires oxygen.

Cellular Respiration

The process that releases energy by breaking down glucose in the presence of oxygen.

Mitochondrion

The organelle where aerobic respiration occurs; the “powerhouse” of the cell.

Matrix

The fluid-filled space inside mitochondria where the Krebs Cycle takes place.

Cristae

The inner folds of the mitochondrial membrane where the electron transport chain occurs.

Krebs Cycle (Citric Acid Cycle)

A series of reactions in the mitochondrion that produce energy carriers (NADH, FADH₂).

FAD/FADH₂

Electron carrier molecules that transport high-energy electrons to the electron transport chain.

Role of ATP in cells

ATP stores and releases energy needed for cell functions like active transport and synthesis.

ATP–ADP Cycle

ATP loses a phosphate to release energy and becomes ADP; ADP gains a phosphate to become ATP again.

Overall equation for photosynthesis

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.

Role of light and chlorophyll

Light excites electrons in chlorophyll, starting energy transfer for photosynthesis.

Steps of photosynthesis

Light-dependent reactions (in thylakoids) make ATP and NADPH → Calvin Cycle (in stroma) uses them to make glucose.

Limiting factors of photosynthesis

Light intensity, carbon dioxide levels, and temperature all affect photosynthesis rate.

Purpose of glycolysis

To split glucose into pyruvate and make 2 ATP and NADH.

Anaerobic vs. aerobic respiration

Anaerobic doesn’t use oxygen and makes less ATP; aerobic uses oxygen and makes much more ATP.

Alcoholic fermentation

Converts pyruvate to ethanol and CO₂; used by yeast.

Lactic acid fermentation

Converts pyruvate to lactic acid; occurs in muscles during low oxygen.

Overall equation for aerobic respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.

Krebs Cycle summary

Breaks down pyruvate into CO₂, producing NADH and FADH₂ for the electron transport chain.

Electron Transport Chain function

Uses energy from electrons to pump hydrogen ions and make large amounts of ATP.

Efficiency of aerobic respiration

Aerobic respiration makes about 36 ATP per glucose, much more than glycolysis alone.

Relationship between photosynthesis and respiration

Photosynthesis stores energy in glucose; respiration releases it — they are opposite processes.

Energy transfer in ecosystems

Energy flows from the sun → producers (autotrophs) → consumers (heterotrophs).

How organisms use energy

Organisms use ATP from cellular respiration to grow, repair, and maintain homeostasis.