Capturing and Using Energy - Metabolism Lecture 7

Flashcards covering key concepts from the 'Capturing and Using Energy' lecture, including photosynthesis and aerobic/anaerobic respiration.

What is the definition of "food" in terms of biology?

Food refers to macromolecules, proteins, lipids, and other organic molecules that contain energy stored in their chemical bonds.

What are autotrophs?

Autotrophs are producers that use sunlight as an energy source to produce their own organic compounds (like glucose) from CO2.

What are photoautotrophs?

Photoautotrophs are a type of autotroph that uses sunlight to make glucose from CO2 through photosynthesis.

What are heterotrophs?

Heterotrophs are consumers that obtain energy by consuming organic compounds originally made by autotrophs.

What are photons?

Photons are packets or bursts of light energy that travel in waves.

How does the energy of a photon relate to its wavelength?

Higher energy photons have shorter wavelengths, while lower energy photons have longer wavelengths.

What are pigments in the context of light energy?

Pigments are light-absorbing molecules that only absorb specific wavelengths of light.

Why do plants appear green?

Plants appear green because green wavelengths of light are reflected, not absorbed, by their pigments.

Name the main pigments used by photoautotrophs.

Chlorophyll a and Chlorophyll b are the main pigments used by photoautotrophs.

Which chlorophyll is considered the most important?

Chlorophyll A is considered the most important, with Chlorophyll B acting as a helper.

What color do carotenoids typically appear?

Carotenoids typically appear orange or reddish.

What is the advantage for plants to use multiple pigments?

Using multiple pigments helps plants absorb more sunlight across different wavelengths.

What is the primary role of photosynthesis?

Photosynthesis uses energy from sunlight to synthesize sugar from CO2, providing most biologically available energy on Earth.

Where does photosynthesis primarily occur in a plant leaf?

Photosynthesis occurs in the leaf mesophyll cells.

What are stomata and what is their function?

Stomata are small gaps, like mouths, on the leaf's surface that open and close to allow gas exchange (CO2 in, O2 out) and water vapor to leave.

What is the semifluid interior of the chloroplast called?

The semifluid interior of the chloroplast is called the stroma.

What are thylakoid membranes within the chloroplast?

Thylakoid membranes are folded, stacked inner membranes within the chloroplast.

How are chloroplasts thought to have evolved?

Chloroplasts are thought to have evolved through endosymbiosis, where a bacteria cell was engulfed and evolved into a chloroplast.

What are photosystems?

Photosystems are clusters of pigments and proteins embedded in the thylakoid membrane that capture light energy.

What are the two main stages of photosynthesis?

The two main stages of photosynthesis are light-dependent reactions and light-independent reactions (Calvin-Benson cycle).

What is the goal of the light-dependent reactions?

The goal of light-dependent reactions is to capture light energy and store it temporarily in ATP and NADPH.

Where do light-dependent reactions occur?

Light-dependent reactions occur at the thylakoid membrane.

What is the role of NADPH in photosynthesis?

NADPH is a coenzyme electron carrier that carries electrons to another part of the reaction.

What is the goal of the light-independent reactions (Calvin-Benson cycle)?

The goal of light-independent reactions is to use the ATP and NADPH from the light-dependent reactions to convert CO2 into sugar (glucose).

Where do light-independent reactions occur?

Light-independent reactions occur in the stroma of the chloroplasts.

What happens to electrons released by chlorophyll pigments during light-dependent reactions?

The highly energized electrons enter an electron transfer chain on the thylakoid membrane.

How is the lost electron in the photosystem replaced during light-dependent reactions?

The lost electron is replaced by an electron derived from the splitting of water molecules.

What is electron transfer phosphorylation?

Electron transfer phosphorylation is the process where energy from the electron transfer chain is used to actively transport H+ ions into the thylakoid compartment, creating a concentration gradient that drives ATP formation via ATP synthase.

What is the specialized protein channel through which H+ ions flow to produce ATP?

ATP synthase is the protein channel through which H+ ions flow down their concentration gradient to drive ATP formation.

What is the key enzyme that catalyzes the Calvin-Benson Cycle?

Rubisco is the key enzyme that catalyzes the Calvin-Benson Cycle, 'fixing' inorganic carbon into glucose.

What is the outcome of the Calvin-Benson Cycle?

The Calvin-Benson Cycle 'fixes' inorganic carbon from CO2 into glucose, using ATP and NADPH.

What is C3 photosynthesis?

C3 photosynthesis is the most basic form where CO2 is captured by rubisco and fixed into a 3-carbon molecule.

What is photorespiration?

Photorespiration is a process where rubisco binds to O2 instead of CO2, consuming O2 and releasing CO2, resulting in a net energy loss for the plant.

Under what conditions does photorespiration occur at high rates?

Photorespiration occurs at high rates when stomata are closed (limiting CO2 intake), leading to a buildup of oxygen, which rubisco then binds to.

What is C4 photosynthesis?

C4 photosynthesis is a pathway where CO2 is fixed first in mesophyll cells, then moved to interior bundle sheath cells for the Calvin Cycle, which reduces photorespiration.

What is CAM photosynthesis?

CAM photosynthesis involves CO2 uptake only at night (when stomata are open), storage in a vacuole, and then the Calvin Cycle proceeds during the daytime.

What is the primary benefit of CAM photosynthesis?

The primary benefit of CAM photosynthesis is that it reduces water evaporation by only opening stomata at night.

What type of separation is characteristic of C4 photosynthesis?

C4 photosynthesis exhibits spatial separation of carbon fixation and the Calvin Cycle.

What type of separation is characteristic of CAM photosynthesis?

CAM photosynthesis exhibits temporal separation (time-based) of CO2 uptake and the Calvin Cycle.

Where are C3 plants most commonly found?

C3 plants are found in tropical to temperate regions and represent about 85% of global plant species.

Where are CAM plants typically found?

CAM plants are typically found in dry deserts and represent about 8% of plant species.

What is cellular respiration?

Cellular respiration refers to metabolic reactions that convert stored energy in 'food' (like glucose) into usable energy (ATP).

What are the two main types of cellular respiration?

The two main types are aerobic respiration (occurs with oxygen) and anaerobic respiration (occurs without oxygen).

What is the overall equation for aerobic respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O + 36 ATP

What are the three main steps of aerobic respiration?

The three main steps of aerobic respiration are Glycolysis, the Krebs Cycle, and the Electron Transfer Chain.

Where does glycolysis occur?

Glycolysis occurs in the cytoplasm.

What are the main products of glycolysis from one glucose molecule?

Glycolysis produces two pyruvates, 2 net ATP, and 2 NADH from one glucose molecule.

Where do Acetyl-CoA formation and the Krebs Cycle occur?

Acetyl-CoA formation and the Krebs Cycle occur in the mitochondria.

What happens to pyruvate before entering the Krebs Cycle?

Pyruvate is broken down into acetyl-CoA before entering the Krebs Cycle.

What is the total typical energy yield from aerobic respiration?

The total typical energy yield from aerobic respiration is approximately 36 ATP (2 from glycolysis, 2 from Krebs Cycle, ~32 from electron transfer).

What is fermentation?

Fermentation is the anaerobic metabolism of carbohydrates.

How much ATP is produced during anaerobic respiration (fermentation)?

Only 2 ATP are produced during anaerobic respiration, solely from glycolysis.

Name two types of fermentation and where they occur.

Alcoholic fermentation (baking, wine, beer) and Lactate fermentation (cheese, yogurt, some skeletal muscles).

What is the role of oxygen at the end of the electron transfer chain in aerobic respiration?

Oxygen acts as the final electron acceptor at the end of the electron transfer chain, forming water.

Besides glucose, what other molecules can be used to make ATP through cellular respiration?

Other organic molecules like proteins and lipids (macromolecules) can also be used to make ATP.