Other AP Biology Unit 5 Concepts

What can yeast do when oxygen is present?

Yeast perform aerobic respiration when oxygen is available.

What can yeast do when oxygen is absent?

Yeast switch to alcohol fermentation when oxygen is low.

What gas is released by both respiration and fermentation?

Carbon dioxide (CO2).

How much ATP is made during glycolysis?

2 net ATP per glucose.

Is ATP produced directly during fermentation?

No, ATP is made during glycolysis before fermentation.

When oxygen is present, where does pyruvate go after glycolysis?

Into the mitochondria for the citric acid cycle.

Where does the H from NADH end up during respiration?

It combines with oxygen to form water at the end of the ETC.

What gas is produced by both respiration and fermentation?

Carbon dioxide.

What does the yeast lab measure to study metabolism?

The rate of CO2 production.

What factors can affect the rate of CO2 production by yeast?

Temperature, yeast concentration, and food source.

Why do yeast release enzymes into their environment?

To break down food externally into molecules small enough to absorb.

Why are yeast good model organisms for this lab?

They are eukaryotic, easy to handle, inexpensive, and safe.

What type of respiration can yeast perform if oxygen is available?

Aerobic respiration.

What happens to yeast if they are too cold during the experiment?

They respire slower because enzymes work less efficiently.

Why is warm water used in the yeast lab?

To keep yeast near their optimal temperature (around 37°C).

What is measured with the Vernier CO2 probe?

The concentration of carbon dioxide over time.

What is the control in the yeast food experiment?

Yeast mixed with only water.

Predicted result for yeast + water

No CO2 produced; no sugar for energy.

Predicted result for yeast + sucrose (disaccharide)

High CO2 production; plenty of sugar for respiration.

Predicted result for yeast + agave (monosaccharide)

High CO2 production; simple sugar easily metabolized.

Predicted result for yeast + flour (complex carbohydrate)

Low CO2 production; starch is too complex for quick digestion.

Predicted result for yeast + Splenda (artificial sweetener)

Low or no CO2; artificial sugars can’t be metabolized.

Predicted result for yeast + honey (monosaccharide)

High CO2 production; contains simple sugars.

What is the independent variable in the yeast lab?

Type of food source.

What is the dependent variable in the yeast lab?

Rate of CO2 production.

Why is rinsing equipment important between trials?

To avoid contamination between sugar solutions.

Why is oxygen important for yeast respiration?

It acts as the final electron acceptor in aerobic respiration.

What does fermentation regenerate so glycolysis can continue?

NAD+.

During fermentation, pyruvate is converted to what molecules?

Ethanol and CO2.

What happens to NADH during fermentation?

It is oxidized to regenerate NAD+.

What kind of energy does glucose store?

Chemical energy.

What is the main energy product of cellular respiration?

ATP.

Compare respiration and combustion: same reactants and products

Both use O2 and glucose; both produce CO2 and H2O.

How is energy release different in respiration vs combustion?

Respiration releases energy slowly in ATP; combustion releases it quickly as heat and light.

What type of reactions are respiration and combustion?

Both are exergonic reactions.

Why does respiration occur in many small steps instead of one?

To capture energy efficiently as ATP instead of losing it as heat.

Why are NAD and FAD needed in respiration?

They safely carry electrons from glucose to the ETC.

Why can’t cells convert glucose directly to ATP?

It would release too much energy at once and damage the cell.

Where does glycolysis occur?

In the cytoplasm.

Where does the citric acid cycle occur?

In the mitochondrial matrix.

Where does the electron transport chain occur?

In the inner mitochondrial membrane.

Is glycolysis aerobic or anaerobic?

Anaerobic.

Is the citric acid cycle aerobic or anaerobic?

Aerobic (requires O2 indirectly).

Is the electron transport chain aerobic or anaerobic?

Aerobic (requires oxygen directly).

Inputs and outputs of glycolysis

Input: Glucose, 2 ATP, NAD+; Output: 2 pyruvate, 2 NADH, 2 net ATP.

Inputs and outputs of citric acid cycle

Input: Acetyl-CoA, NAD+, FAD; Output: CO2, NADH, FADH2, ATP.

Inputs and outputs of ETC

Input: NADH, FADH2, O2; Output: H2O, NAD+, FAD, ~30 ATP.

How much ATP per glucose from glycolysis?

2 ATP (net).

How much ATP per glucose from the citric acid cycle?

2 ATP.

How much ATP from oxidative phosphorylation?

About 30–32 ATP.

Which process makes more ATP: glycolysis or ETC?

The ETC (oxidative phosphorylation).

What is glucose a rich source of?

Chemical energy stored in bonds.

What is substrate-level phosphorylation?

Direct transfer of a phosphate group to ADP to form ATP.

What is oxidative phosphorylation?

ATP production using a proton gradient and ATP synthase.

Where does substrate-level phosphorylation occur?

In glycolysis and the citric acid cycle.

Where does oxidative phosphorylation occur?

In the inner mitochondrial membrane.

How much ATP does substrate-level phosphorylation make per glucose?

About 4 total ATP.

How much ATP does oxidative phosphorylation make per glucose?

About 30–32 ATP.

Order of energy content: glucose, NADH, FADH2, ATP

Glucose > NADH > FADH2 > ATP.

Which molecule has the most energy?

Glucose.

Which molecule has the least energy?

ATP.

Which molecule has the right energy to power cell reactions?

ATP.

Which has more energy, NAD+ or NADH?

NADH (it carries electrons).

What does LEO the lion say about oxidation?

Loss of Electrons is Oxidation.

What does GER mean in reduction?

Gain of Electrons is Reduction.

What is oxidation?

Loss of electrons.

What is reduction?

Gain of electrons.

Theory explaining mitochondria origin

Endosymbiotic theory: mitochondria were once free-living prokaryotes.

Do prokaryotes have mitochondria?

No; they lack membrane-bound organelles.

Can prokaryotes perform cellular respiration?

Yes, across their cell membrane.

Where does glycolysis occur in prokaryotes?

In the cytoplasm.

Compare glycolysis, lactic acid fermentation, and alcohol fermentation

Glycolysis: glucose → pyruvate + ATP; Lactic: pyruvate → lactate; Alcohol: pyruvate → ethanol + CO2.

ATP yield from glycolysis-based fermentation

2 ATP per glucose.

Oxygen requirement for fermentation

None (anaerobic).

Products of lactic acid fermentation

Lactic acid and NAD+.

Products of alcohol fermentation

Ethanol, CO2, and NAD+.

What organisms do alcohol fermentation?

Yeast and some bacteria.

What organisms do lactic acid fermentation?

Muscle cells and some bacteria.

What is the purpose of fermentation?

To regenerate NAD+ so glycolysis can continue.

In the pea lab, which seeds had higher respiration rates?

Germinating peas.

Why did germinating peas produce more CO2?

They were metabolically active and performing aerobic respiration.

Why did non-germinating peas produce little or no CO2?

They were dormant and not respiring.

What did glass beads show in the pea lab?

They served as a control to confirm CO2 came from biological activity.

What was the main claim of the pea lab?

Germinating peas have a higher rate of cellular respiration than non-germinating peas.

What evidence supported the pea lab claim?

Higher CO2 production rates in germinated peas across all groups.

What reasoning linked the evidence to the claim?

Active metabolism in germinating seeds increases ATP demand and CO2 output.

Name three controls in the pea lab

Temperature, air composition, number/volume of peas per chamber.

Why is temperature a control in the pea lab?

To ensure differences in CO2 come from respiration, not heat effects.

Why were glass beads used?

To equalize volume and surface area in control chambers.

Why do germinating seeds respire more?

They use stored energy for growth, requiring more ATP.

What is seed dormancy?

A resting state preventing germination until favorable conditions.

Why is dormancy beneficial?

Prevents germination during poor conditions, increasing survival.

What protects the embryo inside the seed?

The seed coat.

What structures are found inside a seed?

Plumule, epicotyl, cotyledons, and hypocotyl.

Function of cotyledons

Provide stored nutrients for the embryo.

Function of endosperm

Nourishes the developing embryo.

What is germination?

The process by which a seed begins to grow into a plant.

Do all seeds have the same germination requirements?

No, they vary by species and environment.

What is imbibition?

Initial water absorption by a dry seed, leading to swelling and enzyme activation.