AP Bio: Cellular Energetics Test

First law of thermodynamics and one example

the energy of the universe is constant; energy can be transferred and transformed, but it cannot be created or destroyed

Second law of thermodynamics and one example

During every energy transfer or transformation,

some energy is unusable and is often lost as heat.

Every energy transfer or transformation increases the

entropy(chaos, disorder) of the universe

What is the role of enzymes in reactions?

Enzymes speed up chemical reactions by lowering activation energy. They are catalysts.

Contrast exergonic and endergonic reactions

Exergonic- proceeds with a net release of free energy and is spontaneous; ∆G is negative, increases stability, downhill reaction, reactants have more energy than products (ex. cellular respiration, digestion)

Endergonic- absorbs free energy from its surroundings and is nonspontaneous; ∆G is positive, decrease in stability, uphill reaction, reactants have less energy than products (ex. photosynthesis, protein synthesis)

What is a coupled reaction?

Energy released from exergonic reactions that drives endergonic reactions

What is the role of ATP in:

a. Exergonic reactions

b. Endergonic reactions

a. ATP energy released in exergonic reactions is used to synthesize ATP by combining ADP with a phosphate molecule. This ATP can then be hydrolyzed, removing a phosphate group and releasing energy that can be used to fuel endergonic reactions.

b. ATP transfers a phosphate group to the reacting molecule of the endergonic reaction.

Define:

a. Metabolism

b. Catabolism

c. Anabolism

a. Metabolism is the totality of an organism’s chemical

reactions (ex. eating food converts energy for use in the body)

b. Catabolism releases energy by breaking down complex molecules into simpler compounds (ex. digestion of food)

c. Anabolism consume energy to build complex molecules from simpler ones (ex. synthesis of protein from amino acids, bone development)

Contrast enthalpy and entropy

Enthalpy is the amount of energy released or absorbed in a system whereas, entropy is the measure of disorderness in a system.

What is a redox reaction?

Chemical reactions that transfer electron between reactants

Write the chemical reactions for photosynthesis and cellular respiration. Tell what gets reduced and what gets oxidized.

Photosynthesis:

6 CO2 + 12 H2O + Light energy → C6H12O6 + 6 O2 + 6 H2O

Carbon dioxide is reduced to glucose. Water is oxidized to oxygen.

Cellular Respiration:

C6H12O6(glucose) + O2(oxygen) —> 6 CO2(carbon dioxide) + 6 H2O(water) + ATP(energy)

Glucose is oxidized to carbon dioxide. Oxygen is reduced into water.

Differentiate between potential and kinetic energy

Potential energy- energy that matter possesses because of its location or structure

Kinetic Energy- energy associated with motion

During what type of reaction will there be a positive ΔG? Negative ΔG? Which one is spontaneous and which one is nonspontaneous?

Endergonic reaction will occur for a positive ΔG and an exergonic reaction will occur for a negative ΔG. Endergonic is non spontaneous and exergonic is spontaneous.

What happens to the heat generated by an organism during metabolic reactions?

Heat can aid in the movement of particles because temperature speeds up their movement or energy can be used to drive active transport.

What happens to a system at chemical equilibrium? (Can it perform work?)

At equilibrium, forward and reverse reactions occur at the same rate; it is a state of maximum stability

What is the equation for cellular respiration?

a. What is being oxidized?

b. What is being reduced?

C6H12O6 + 6O2 —> 6H2O + 6CO2 + ATP

a. glucose is oxidized

b. oxygen is reduced

What is the purpose of cellular respiration?

To generate ATP energy

Where does each occur:

a. Glycolysis

b. Acetyl CoA Prep

c. Kreb’s Cycle

d. Electron Transport Chain

a. Glycolysis occurs in the cytosol —> makes 2 ATP

b. Acetyl CoA Prep occurs in the mitochondrial matrix

c. Kreb’s Cycle occurs in the mitochondrial matrix —> makes 2 ATP

d. ETC occurs in the crustal —> makes 34 ATP

Describe Glycolysis

The first stage in cellular respiration that breaks down glucose into two pyruvate molecules

Describe Acetyl CoA Prep and the Kreb’s Cycle

Acetyl CoA Prep- pyruvate must be converted to Acetyl CoA to link glycolysis to the Kreb’s cycle

Kreb’s Cycle- metabolic acetyl coA makes 3 NADH and 1 ATP or GTP. This cycle occurs twice, therefore, 6 NADH, 2 FADH2 and 2 ATP are made because of the presence of 2 pyruvate molecules.

Describe the electron transport chain

1. Accepts electrons from NADH and FADH2.

2. electrons pass to the molecules in ETC

3. Hydrogen is released on the opposite side of the membrane when the electrons pass to meet molecules. This creates a high concentration of H+ ions in the intermediate space.

4. 2 electrons + 2 H + ½ O2 —> H2O

5. ATP synthase allows H+ ions to travel down the concentration gradient

6. H+ is added to a phosphate group to ADP to form ATP

Create a drawing that summarizes cellular respiration and shows:

a. Glycolysis – what are the reactants and products?

b. Acetyl CoA Prep

c. Kreb’s Cycle – what are the reactants and products?

d. Electron Transport Chain – what are the reactants and products?

Contrast substrate level and oxidative phosphorylation.

Substrate Level- A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation

Oxidative phosphorylation- accounts for almost 90% of the ATP generated by cellular respiration

Describe chemiosmosis in cellular respiration.

Chemiosmosis- the use of energy in H+ gradient to drive cellular work

1. Electron transfer in the electron transport chain

   causes proteins to pump H+ from the mitochondrial

   matrix to the intermembrane space

2. H+ then moves back across the membrane, passing

   through the protein complex, ATP synthase

3. ATP synthase allow exergonic flow at H+ to drive phosphorylation of ATP

How many ATPs are produced by the following structures?

a. NADH

b. C6H1206

c. FADH2

d. GTP

a. NADH —> 3 ATP

b. Glucose —> 36-38 ATP

c. FADH2 —> 2 ATP

d. GTP —> ATP

Define the following terms:

a. ATP synthase

b. Aerobic respiration

c. Anaerobic respiration

a. ATP Synthase- allow H+ to move down concentration gradient

b. Aerobic Respiration- the presence of oxygen in respiration

c. Anaerobic Respiration- the absence of oxygen in respiration

How can you measure the rate of respiration?

By finding the optimal amount of time of carbon dioxide produced.

Which part of cellular respiration creates the most ATP?

Oxidative Phosphorylation/Electron Transport Chain —> 26-28

Is cellular respiration anabolic or catabolic? Endergonic or exergonic?

Cellular respiration is catabolic because it breaks down glucose to make energy. It’s exergonic because it releases energy after breaking down glucose.

Trace the flow of electrons in cellular respiration.

Electrons from glucose move gradually through the ETC towards oxygen, passing lower energy states releasing energy.

Draw a mitochondrion and label the inner mitochondrial membrane, mitochondrial matrix and intermembrane space. Also label where there is a high concentration of H+ and where there is a low concentration of H+.

What is the difference between FADH2 and NADH?

NADH produces 3 ATP and FADH2 produces 2 ATP. NADH is reduced from NAD+ and FADH2 is reduced from FAD.

Contrast fermentation and cellular respiration.

Fermentation- an aerobic process that is the partial degeneration of sugars without oxygen.

Cellular Respiration- can be both aerobic and anaerobic meaning it can and doesn’t need oxygen.

Compare what happens to an animal cell that is undergoing oxygen debt versus a yeast cell that is undergoing oxygen debt.

Yeast undergoing oxygen debt converts pyruvic acid to ethanol and carbon dioxide. Animals undergoing oxygen debt convert pyruvic acid to lactic acid.

What is the equation for photosynthesis?

a. What is being oxidized?

b. What is being reduced?

6 H2O + 6 CO2 + light energy —> C6H12O6 + 6 O2

a. Water is oxidized into oxygen

b. Carbon dioxide is reduced into glucose.

What role does each play in photosynthesis?

a. Leaf

b. Root

c. Mesophyll cells

d. Chloroplasts

e. Stomata

f. Xylem

a. Leaf- the location of photosynthesis

b. Root- absorbs water and nutrients for the plants

c. Mesophyll cells- cells that contain chloroplasts (30-40 in each cell)

d. Chloroplasts- produce energy from glucose and store energy

e. Stomata- pores on the underside of leaves that open and close; where carbon dioxide enters and oxygen exits.

f. Xylem- plant tissue that transfers water and nutrients from the roots to the plant body.

Where does each happen?

a. Light reaction

b. Calvin cycle

a. Light Reaction occurs in the thylakoids which are located in the chloroplasts

b. Calvin cycle occurs in the stroma (inner space of chloroplasts)

Describe what happens during an what is created by the following processes:

a. Cyclic electron flow

b. Noncyclic electron flow

a. Cyclin electron flow occurs in photosystem 1 and uses light energy as its source of energy. The wavelengths used are 700 nm. The electrons are recycled back to the cytochrome complex and ATP is created. The products go to the Calvin cycle.

b. Noncyclic electron flow occurs in both photosystem II and I. It uses light energy as its source of energy. The wavelengths used are 680-700nm. The electrons are removed from water and pass through PSI and PSII. ATP and NADPH and Oxygen are created. They head to the Calvin cycle.

What is the role of water in the light reactions?

Water is split releasing electrons, hydrogen ions, and oxygen.

What are the reactants and the products of the light reactions?

Reactants: water, sunlight, NADP+ and ADP

Products- oxygen, NADPH and ATP

Differentiate between photosystem I and photosystem II.

Cyclic electron flow only involves PSI whereas noncyclic electron flow involves both PSI and PSII. Cyclic electron flow also only creates ATP whereas noncyclic electron flow creates ATP and NADPH.

Describe the Calvin cycle.

The Calvin cycle is located in the stroma. The reactants are ATP, NADPH, and CO2. The products are ADP, NADP+ and glucose. The energy source is ATP. The first phase is carbon fixation. Rubisco fixes carbon dioxide in ribulose diphosphate. The second phase is reduction where NADPH reduces by adding electrons creating G3P (glucose). The third phase is regeneration which regenerates ribulose biphosphate (the CO2 acceptor).

Why was the Calvin Cycle called the dark reactions?

The Calvin cycle only occurs at night and doesn't need sunlight.

Contrast C3, C4 and CAM plants.

a. How and when do they capture carbon dioxide?

b. When do they go through the light reactions?

c. What are examples of each?

d. What environment do they work best in?

a. C3 plants use rubisco to capture CO2, C4 plants capture CO2 with the chemical PEP, and CAM plants use organic acids.

b. C3 plants —> day; C4 plants —> day/night; CAM plants —> night

c. C3 plants (ex. soybean, rice); C4 plants (ex. sugarcane, corn) CAM plants (ex. cacti, pineapple)

d. C3- cool, moist climate; C4 arid, hot, dry climates; CAM- arid, hot, and dry climates

11. What is photorespiration? Why is it bad for the plant? What is the evolutionary significance of it?

In photorespiration, rubisco adds O2 instead of CO2 in the Calvin cycle, producing a two-carbon compound. Photorespiration decreases photosynthetic output by consuming ATP, O2, and organic fuel and releasing CO2 without producing any ATP or sugar. The evolutionary significance is that rubisco developed before there was a high concentration of O2 in atmosphere.

What is the relationship between wavelength of light and photosynthetic activity? Quantity of energy?

Plant pigment molecules absorb only light in the wavelength range of 700 nm to 400 nm; this range is referred to as photosynthetically-active radiation. Different colors of light can either increase/decrease the rate of photosynthesis.

What wavelengths of light are most important to plants? Least important?

Red light falling in the range of wavelength 660-760 nm is the most effective for photosynthesis. Green light falling in the range of wavelength 500-580 nm is the least effective for photosynthesis.

Is photosynthesis endergonic or exergonic? Explain.

Endergonic because plants cannot initiate the process of photosynthesis until they absorb light energy. Chlorophyll in the plant's cells absorbs the light energy, and once absorbed, that energy is used for the photosynthesis reaction to occur.

Why do the chloroplasts of plants appear green?

The green pigment in leaves is chlorophyll, which absorbs red and blue light from sunlight. Therefore, the light the leaves reflect is diminished in red and blue and appears green.

What are carotenoids? Why are they important?

They are accessory pigments that absorb excessive light that would damage chlorophyll.

How is chemiosmosis involved in photosynthesis?

During light-dependent reactions of photosynthesis, chemiosmosis is the process by which light energy is converted to chemical energy in the form of ATP to be used in dark reactions.

Draw a chloroplast including the thylakoid, thylakoid space, stroma and grana. Label where there is a high concentration of H+ and a low concentration of H+. Label where the light reactions and the Calvin cycle take place.

How can you measure the rate of photosynthesis?

• Measuring the uptake of CO2.

• Measuring the production of O2.

In autotrophic bacteria, where is the chlorophyll located?

In the in folded plasma membrane.

Where are the ATP synthase complexes located?

in the inner membrane of mitochondria

In photosynthesis, what is oxygen a direct by-product of?

Water/H2O

Why must P680 be a strong oxidizing agent?

It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.

Differentiate between C4 and CAM photosynthesis.

Plants that use CAM photosynthesis collect sunlight during the day and fix CO2 molecules at night. Answer: The primary distinction between C4 and CAM plants is how they minimise water loss. C4 plants move CO₂ molecules to reduce photorespiration, whereas CAM plants decide when to extract CO₂ from the environment.

Why is C4 and CAM photosynthesis more efficient in tropical climates?

Both have adaptations to arid conditions, because they are more efficient in the conservation of water.

Compare what happens to an animal cell that is undergoing oxygen debt versus a yeast cell that is undergoing oxygen debt.

Yeast undergoing oxygen debt converts pyruvic acid to ethanol and carbon dioxide. Animals undergoing oxygen debt convert pyruvic acid to lactic acid.