Unit 3: Matter and Energy Flashcards

Comprehensive review flashcards covering Unit 3: Matter and Energy, including ATP structure and dynamics, photosynthesis, cellular respiration, anaerobic fermentation, trophic levels, and ecological energy flow and nutrient cycling.

What is the primary function of ATP in living organisms?

ATP (adenosine triphosphate) is the high-energy form of energy that is directly usable by your cells to perform cellular work.

What are the three structural components of an ATP molecule?

An ATP molecule is composed of adenine, a ribose sugar, and three phosphate groups.

What process is shown in this diagram, and what occurs structurally when ATP releases energy to become ADP?

The diagram shows the breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and an inorganic phosphate ($P$). Energy is released because ATP is a high-energy, unstable molecule; removing the terminal phosphate breaks a high-energy bond, releasing free energy and leaving a lower-energy, more stable ADP molecule.

How does the ATP-ADP cycle function in cells?

Energy obtained from food/cellular respiration is used to add an inorganic phosphate ($P$) to ADP, converting it into ATP. When cells need energy for cellular work, a phosphate is removed from ATP, releasing free energy and regenerating ADP.

How does the ATP yield from the breakdown of carbohydrates compare to that of lipids and proteins?

Carbohydrates (such as glucose) yield approximately $36\,\text{ATP}$ molecules; lipids yield significantly more energy, with one triglyceride producing approximately $146\,\text{ATP}$ molecules; proteins store approximately the same amount of energy as carbohydrates.

What are the word and balanced chemical equations for photosynthesis?

Word equation: carbon dioxide + water + sunlight $\rightarrow$ glucose + oxygen Chemical equation: $6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2$

Identify the primary internal structures of the chloroplast shown in this diagram and state their definitions.

1. Stroma: The fluid-filled space enclosed by the inner membrane where the Calvin cycle takes place.
2. Thylakoid: Disc-shaped, membrane-bound sacs containing pigments where the light-dependent reactions occur.
3. Granum (plural: grana): A stack of thylakoids (interconnected by lamellae).

Based on the absorbance spectra shown for chlorophyll a and chlorophyll b, why do leaves appear green to the human eye?

Chlorophyll pigments absorb light predominantly in the blue (around $400\text{--}500\,\text{nm}$) and red (around $600\text{--}700\,\text{nm}$) wavelengths of the visible spectrum, while reflecting green light (around $500\text{--}600\,\text{nm}$). Because green light is reflected into our eyes, the plant appears green.

What are the location, reactants, and products of the light-dependent reactions of photosynthesis?

Location: Thylakoid membrane. Reactants: Light energy and water ($H_2O$) (along with ADP and $NADP^+$). Products: Oxygen ($O_2$), ATP, and NADPH (which are used to power the Calvin cycle).

What are the location, reactants, and products of the Calvin cycle (light-independent reactions)?

Location: Stroma. Reactants: Carbon dioxide ($CO_2$), along with ATP and NADPH from the light reactions. Products: Simple sugars (glucose / $C_6H_{12}O_6$), along with ADP and $NADP^+$.

What are the word and balanced chemical equations for cellular respiration?

Word equation: glucose + oxygen $\rightarrow$ carbon dioxide + water + ATP Chemical equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$

Why is cellular respiration considered an aerobic process, and why is its chemical equation written with multiple arrows?

It is considered aerobic because it requires oxygen ($O_2$). It is written with multiple arrows because cellular respiration is not a single reaction, but a complex series of metabolic reactions.

Identify the structural features of the mitochondrion shown in the diagram and describe their roles in cellular respiration.

1. Outer Membrane: A selectively permeable membrane that encloses the entire organelle.
2. Inner Membrane / Cristae: Folds inward to dramatically increase the surface area available for the electron transport chain and ATP synthase.
3. Inner Mitochondrial Matrix: A thick fluid enclosed by the inner membrane where the Krebs cycle takes place.

What are the location, reactants, products, and net ATP gain of glycolysis?

Location: Cytoplasm (cytosol). Reactants: Glucose (sugar). Products: 2 pyruvate (pyruvic acid), NADH, and ATP. Net gain: $2\,\text{ATP}$ molecules (anaerobic process).

What are the location, reactants, products, and net ATP gain of the Krebs cycle?

Location: Inner mitochondrial matrix. Reactants: Pyruvate (converted into Acetyl CoA). Products: Carbon dioxide ($CO_2$), ATP, NADH, and $FADH_2$. Net gain: $2\,\text{ATP}$ molecules.

According to the diagram, what are the two coordinated parts of the electron transport stage in mitochondria, and how is ATP generated?

1. Electron transport chain: NADH transfers high-energy electrons, releasing energy used to pump $H^+$ ions across the inner membrane. Oxygen acts as the final electron acceptor, combining with electrons and $H^+$ to form water ($H_2O$).
2. ATP production in ATP synthase: The accumulated $H^+$ ions flow back down their gradient through ATP synthase, causing the protein to spin and generate ATP from ADP ($34\,\text{or more ATP}$).

What is fermentation, and why do cells undergo it in the absence of oxygen?

Fermentation is an anaerobic cellular process that follows glycolysis when oxygen is absent. It does not produce additional ATP directly, but it regenerates $NAD^+$ from NADH so that glycolysis can continue operating to produce a net of $2\,\text{ATP}$.

How do lactic acid fermentation and alcoholic fermentation differ in products and practical/commercial applications?

Lactic acid fermentation produces lactic acid; it occurs in muscle cells during short bursts of intense activity (leading to muscle fatigue) and is commercially used to produce the sour taste in cheeses and yogurt. Alcoholic fermentation occurs in microorganisms like yeast under anaerobic conditions, producing alcohol and carbon dioxide ($CO_2$); it is commercially used to make beer, wine, and bread (where $CO_2$ causes dough to rise).

What is the difference between an autotroph and a heterotroph?

An autotroph (producer) makes its own food by taking in inorganic molecules like $CO_2$ and converting light energy from the sun into chemical organic molecules. A heterotroph (consumer) cannot synthesize its own organic molecules and must consume other organisms for food and energy.

What are the four consumer trophic levels, and what is an example of an organism at each level?

1. Primary consumer: Herbivore that eats producers (e.g., caterpillar, grasshopper, rabbit).
2. Secondary consumer: Carnivore or omnivore that eats primary consumers (e.g., bird, frog).
3. Tertiary consumer: Predator that eats secondary consumers (e.g., snake, wolf).
4. Quaternary consumer / Apex predator: Top predator in the food chain (e.g., eagle, lion).

What is the difference between a food chain and a food web?

A food chain is a single, linear model that links organisms by their feeding relationships in a hierarchical sequence; a food web is an interconnected network of multiple food chains showing complex feeding relationships across an ecosystem.

What ecological principles of energy transfer and loss are illustrated by this energy pyramid?

Only approximately $10\%$ of energy is conserved and transferred from one trophic level to the next ($100\%$ primary producers $\rightarrow$ $10\%$ primary consumers $\rightarrow$ $1\%$ secondary consumers $\rightarrow$ $0.1\%$ third-level consumers $\rightarrow$ $0.01\%$ apex predators). The remaining $90\%$ of energy is lost as heat, used for metabolic life processes/growth, or transferred to decomposers via waste and dead matter.

How does the fundamental behavior of energy differ from the behavior of matter in an ecosystem?

Energy flows unidirectionally through an ecosystem; it cannot be recycled, is progressively lost as heat, and must be continuously supplied by the sun. Matter cycles continuously within an ecosystem between abiotic and biotic forms and remains perpetually available.

What role do photosynthesis and cellular respiration play in the carbon and oxygen cycles?

Photosynthesis removes inorganic carbon dioxide ($CO_2$) from the atmosphere and uses water and sunlight to produce organic molecules (glucose / $C_6H_{12}O_6$) and release oxygen ($O_2$). Cellular respiration consumes oxygen ($O_2$) to break down glucose, releasing carbon dioxide ($CO_2$) and water back into the environment, continuously cycling carbon and oxygen between organic and inorganic forms.