Photosynthesis and Cellular Respiration Review

Vocabulary practice flashcards covering key topics, chemical equations, pathways, and short answer concepts for photosynthesis and cellular respiration.

Parts of an ATP molecule

An adenine nitrogenous base, a 5-carbon ribose sugar, and three phosphate groups.

Parts of an ADP molecule

An adenine nitrogenous base, a 5-carbon ribose sugar, and two phosphate groups.

Photosynthesis

The process by which autotrophs capture light energy and use it to convert carbon dioxide and water into oxygen and high-energy sugars.

Cellular respiration

The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

Heterotroph

An organism that obtains energy and organic food molecules by consuming other organisms.

Autotroph

An organism that captures energy from sunlight or chemicals to produce its own food.

Molecule that stores energy

ATP (adenosine triphosphate) stores immediate, usable chemical energy; glucose and glycogen store larger amounts of energy for long-term storage.

Amount of energy stored in ATP

ATP stores a small, readily usable amount of energy suitable for short-term cellular work; a single glucose molecule stores more than 90 times the chemical energy of a molecule of ATP.

Formula of photosynthesis

$6CO_2 + 6H_2O \xrightarrow{\text{light}} C_6H_{12}O_6 + 6O_2$ (carbon dioxide + water in the presence of light produces glucose + oxygen).

Formula of respiration

$6O_2 + C_6H_{12}O_6 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$ (oxygen + glucose produces carbon dioxide + water + energy).

Pigment in chloroplast

Chlorophyll (primarily chlorophyll a and chlorophyll b), which absorbs blue-violet and red light while reflecting green light.

Thylakoid

A flattened, saclike photosynthetic membrane found in chloroplasts where the light-dependent reactions take place; arranged in stacks called grana.

Calvin cycle location

Takes place in the stroma, the fluid portion of the chloroplast located outside the thylakoids.

Photosystem

A cluster of chlorophyll and other photosynthetic pigments embedded within the thylakoid membrane that absorbs light energy.

Name of light-independent cycle

The Calvin cycle.

How NADP+ turns into NADPH

$NADP^+$ accepts and holds two high-energy electrons along with a hydrogen ion ($H^+$).

Factors that affect photosynthesis

Temperature, light intensity, and the availability of water.

How energy is released from ATP

Energy is released by breaking the high-energy chemical bond between the second and third phosphate groups, converting ATP into ADP.

Difference between calorie and Calorie

A calorie (lowercase 'c') is the amount of energy needed to raise the temperature of 1 gram of water by $1^\circ\text{C}$; a dietary Calorie (capital 'C') is a kilocalorie, which equals $1000\text{ calories}$.

Number of carbons in pyruvic acid

3 carbons (pyruvate is a 3-carbon molecule formed by splitting a 6-carbon glucose molecule during glycolysis).

3 stages of cellular respiration

Glycolysis, the Krebs cycle (citric acid cycle), and electron transport chain (with ATP synthesis).

Lactic acid fermentation

An anaerobic process that converts pyruvic acid into lactic acid while regenerating $NAD^+$ to allow glycolysis to continue producing ATP in the absence of oxygen.

Alcoholic fermentation

An anaerobic process carried out by yeasts and microorganisms that converts pyruvic acid into ethyl alcohol and carbon dioxide, regenerating $NAD^+$.

Number of ATP produced in glycolysis

A net yield of 2 ATP molecules per glucose molecule (4 ATP are synthesized, but 2 ATP are consumed).

How carbon dioxide is formed in the Krebs cycle

Carbon atoms are sequentially stripped from pyruvic acid and intermediary carbon molecules and bonded with oxygen to form $CO_2$ as a waste product.

Glycogen

A complex carbohydrate (polysaccharide) stored in muscle and liver tissues that animals break down into glucose to provide sustained energy.

Process used for long term energy

Cellular respiration (aerobic respiration), which steadily produces ATP for physical exertion lasting longer than approximately 90 seconds.

Process used for short term energy

ATP stored directly in muscles and lactic acid fermentation, providing rapid energy for brief bursts of activity lasting up to about 90 seconds.

ATP produced in fermentation

2 ATP molecules per glucose molecule (generated during glycolysis; fermentation itself yields 0 additional ATP, serving only to regenerate $NAD^+$).

ATP produced in cellular respiration

Approximately 36 to 38 ATP molecules per molecule of glucose under complete aerobic conditions.

Time it takes to use energy stored in muscles

ATP already stored in muscle cells is used up in a few seconds (about 2 to 3 seconds), after which lactic acid fermentation sustains short-term activity for roughly 90 seconds.

Steps of the light-dependent reactions

1. Light absorption and water-splitting in Photosystem II produce electrons, $H^+$ ions, and $O_2$. 2. Electrons travel down the electron transport chain, pumping $H^+$ into the thylakoid space. 3. Photosystem I re-energizes electrons to reduce $NADP^+$ to NADPH. 4. $H^+$ ions pass through ATP synthase into the stroma, producing ATP.

Photosynthesis vs. Cellular respiration

Photosynthesis captures energy, removes $CO_2$, and releases $O_2$ and glucose (occurring in chloroplasts); cellular respiration releases energy, consumes $O_2$ and glucose, and produces $CO_2$ and $H_2O$ (occurring in mitochondria). Their overall chemical equations are direct opposites of one another.