Topic 5: Energy transfer in and between organisms

What is photosynthesis?

A reaction in which light energy is used to produce glucose in plants, requiring water and carbon dioxide.

What are the two stages of photosynthesis?

The light dependent stage and the light independent stage.

What factors determine the rate of photosynthesis?

Carbon dioxide concentration, light intensity, and temperature.

Where does photosynthesis occur in plant cells?

In chloroplasts.

What is the role of thylakoid membranes in chloroplasts?

They provide a large surface area for the attachment of chlorophyll, electrons, and enzymes.

What is photolysis?

The splitting of water molecules using light energy during the light dependent reaction.

What are the products of photolysis?

1 molecule of oxygen, 4 protons, and 4 electrons.

What is the purpose of the proton gradient in photosynthesis?

It drives the process of photophosphorylation, leading to ATP synthesis.

What is the Calvin Cycle?

A series of reactions in the light independent stage that converts carbon dioxide into glucose.

What is the function of the enzyme Rubisco?

It catalyzes the fixation of carbon dioxide with ribulose bisphosphate (RuBP).

What is glycolysis?

The first step of both aerobic and anaerobic respiration that occurs in the cytoplasm, converting glucose into pyruvate.

What are the products of glycolysis?

2 molecules of pyruvate, 2 molecules of ATP, and 2 molecules of NADH.

What occurs during the link reaction?

Pyruvate is converted into acetyl coenzyme A, releasing carbon dioxide and reducing NAD.

What is produced in the Krebs Cycle?

2 ATP, 6 NADH, 2 FADH, and 4 CO2 per molecule of glucose.

What occurs during oxidative phosphorylation?

Electrons from NADH and FADH are passed down a chain of protein complexes, leading to ATP production.

What is anaerobic respiration?

A form of respiration that occurs in the absence of oxygen, producing lactate from pyruvate.

How many turns of the Calvin Cycle are needed to produce one molecule of glucose?

6 turns of the Calvin Cycle are required.

What is the role of ATP synthase in photosynthesis?

It synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient.

What is the significance of reduced NADP in photosynthesis?

It is used to reduce glycerate-3-phosphate during the light independent reaction.

What happens to the oxygen produced during photolysis?

It diffuses out through the stomata or is used in respiration.

What is the end product of the light independent reactions?

Glucose is produced from triose phosphate.

What is the role of coenzyme A in cellular respiration?

It combines with acetate to form acetyl coenzyme A during the link reaction.

What is the function of the electron transport chain in respiration?

It facilitates the transfer of electrons, leading to the pumping of protons and ATP synthesis.

What is the role of Complexes I, III, and IV in electron transport?

They use energy from electrons to pump protons across the membrane.

What is the final electron acceptor in the electron transport chain?

Oxygen

What is formed when electrons combine with protons and oxygen?

Water

What creates the proton gradient in mitochondria?

The pumping of protons from the mitochondrial matrix to the intermembrane space.

What is the function of ATP synthase?

It uses the proton motive force to produce ATP.

Define an ecosystem.

An ecosystem includes all organisms living in a particular area and the non-living elements of that environment.

What are biotic factors?

Living factors that affect the distribution and abundance of organisms, such as predators and disease.

What are abiotic factors?

Non-living factors that affect the distribution and abundance of organisms, such as light levels and temperature.

What are autotrophs?

Organisms that produce their own food using energy from the sun.

What are heterotrophs?

Organisms that cannot synthesize their own food and rely on consuming other organisms.

What percentage of chemical energy is typically passed on in a food chain?

Around 10%.

What is net primary productivity (NPP)?

The rate at which energy is transferred into organic molecules that make up new plant biomass after respiratory losses.

What is gross primary productivity (GPP)?

The rate at which energy is incorporated into organic molecules in plants during photosynthesis.

How is NPP calculated?

NPP = GPP - R, where R is the respiratory losses.

What is ammonification?

The process where microbes break down organic matter to ammonia.

What is nitrification?

The conversion of ammonia to nitrate ions by nitrifying bacteria.

What is denitrification?

The conversion of nitrate ions to nitrogen gas by denitrifying bacteria.

What is nitrogen fixation?

The process of converting nitrogen gas into ammonia by nitrogen-fixing bacteria.

What role do mycorrhizae play in ecosystems?

They facilitate the uptake of water and inorganic ions by plants.

What is leaching?

The process by which mineral ions dissolve in rainwater and are carried from the soil to waterways.

What is eutrophication?

The rapid growth of algae in waterways due to excess nutrients, leading to ecosystem decline.

What are the negative effects of nitrogen fertilizers?

They can reduce biodiversity, cause leaching, and lead to eutrophication.

What is the significance of the phosphorus cycle?

It recycles phosphorus, which is essential for biological molecules in ecosystems.

How can the chemical energy stored in dry biomass be estimated?

Using calorimetry in a bomb calorimeter.

What is the relationship between nitrogen-fixing bacteria and leguminous plants?

It is mutualistic, benefiting both organisms.