Biology 110 - Chapters 9-10

Photosynthesis

The process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of sugars.

Cellular Respiration

The metabolic process by which cells convert glucose and oxygen into energy, carbon dioxide, and water.

Chloroplast

The organelle in plant cells where photosynthesis takes place, containing chlorophyll and thylakoids.

Light Reactions

The first stage of photosynthesis that converts solar energy into chemical energy (ATP and NADPH) and produces oxygen as a byproduct.

Calvin Cycle

The second stage of photosynthesis that uses ATP and NADPH to convert carbon dioxide into glucose.

Autotrophs

Organisms that can produce their own food through photosynthesis or chemosynthesis, such as plants and some bacteria.

Heterotrophs

Organisms that obtain organic material by consuming other organisms, such as animals and fungi.

Stomata

Small openings on the surface of leaves that allow for gas exchange, enabling the intake of carbon dioxide and the release of oxygen.

Thylakoids

Membrane-bound structures within chloroplasts where the light reactions of photosynthesis occur.

Chlorophyll

The green pigment in plants that absorbs light energy for photosynthesis, primarily in the blue and red wavelengths.

NADPH

An electron carrier produced in the light reactions that provides reducing power for the Calvin cycle.

ATP

The energy currency of the cell, produced during the light reactions and used in the Calvin cycle.

Rubisco

The enzyme that catalyzes the first step of the Calvin cycle, facilitating the fixation of carbon dioxide.

G3P

A three-carbon sugar produced in the Calvin cycle that can be used to form glucose and other carbohydrates.

Photorespiration

A process that occurs when rubisco binds to oxygen instead of carbon dioxide, leading to a decrease in photosynthetic efficiency.

C4 and CAM Pathways

Alternative photosynthetic pathways that some plants use to minimize photorespiration and maximize carbon fixation in hot, dry environments.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll, converting carbon dioxide and water into glucose and oxygen.

Light-dependent reactions

Reactions that occur in the thylakoid membrane of chloroplasts during photosynthesis. They require light energy to convert ADP and NADP+ into ATP and NADPH, respectively. These reactions also produce oxygen as a byproduct.

Light-independent reactions (Calvin cycle)

The series of chemical reactions in photosynthesis that convert carbon dioxide into glucose molecules. It occurs in the stroma of chloroplasts and does not require light energy. The cycle involves three main steps: carbon fixation, reduction, and regeneration of the starting molecule.

Carbon fixation

The process of incorporating carbon dioxide into organic compounds during the Calvin cycle of photosynthesis.

Factors Affecting Photosynthesis

Various environmental conditions, including light intensity, temperature, carbon dioxide concentration, and water availability, that influence the rate of photosynthesis in plants.

Production of oxygen

One of the significant outcomes of photosynthesis, where oxygen is released as a byproduct during the light-dependent reactions.

Leaf adaptations

The specialized adaptations of leaves, such as their shape, size, and arrangement, that optimize the absorption of sunlight for photosynthesis.

Chloroplast distribution

The strategic arrangement of chloroplasts within plant cells to maximize exposure to light for efficient photosynthesis.

Stomatal control

The regulation of stomatal openings in plant leaves to control the exchange of gases, including carbon dioxide and oxygen, for optimal photosynthesis.

Cyanobacteria

Photosynthetic prokaryotic organisms that can carry out photosynthesis similar to plants and algae, playing a crucial role in Earth's ecosystems.

Photon

A packet of light.

Chlorophyll

The light-absorbing green-coloured pigment that begins the process of photosynthesis.

Chloroplast

A membrane-bound organelle in green plant and algal cells that carries out photosynthesis.

Stroma

The protein-rich semiliquid material in the interior of a chloroplast.

Thylakoid

A disk-shaped sac in the stroma of a chloroplast.

Grana

Stacks of tylakoids.

Lamellae

Groups of unstacked thylakoids between grana.

Thylakoid Membrane

The photosynthetic membrane within a chloroplast that contains light gathering pigment molecules and electron transport chains.

Thylakoid Lumen

A fluid-filled interior space enclosed by the thylakoid membrane.

ATP

A molecule containing three high energy phosphate bonds that acts as the primary energy-transferring molecule in a living organism.

ADP

A molecule containing two high-energy phosphate bonds that may be formed by breaking one of the phosphate bonds in ATP.

NADP+

A compound that accepts one hydrogen atom and two electrons forming NADPH; it is an electron acceptor.

NADPH

A compound that donates one hydrogen aton and two electrons to another molecule, to reform NADP+; it is an electron donor.

Light-dependent reactions

reactions of photosynthesis that use energy from light to produce ATP and NADPH

Carbon Fixation

The process of incorporation CO2 into carbohydrate molecules.

Calvin Cycle

A cyclic set of reactions occurring in the stroma of chloroplasts that fixes the carbon of CO2 into carbohydrate molecules and recycles coenzymes.

Light-independent reactions

The second set of reactions in photosynthesis that do not require light.

Photosystem

A cluster of photosynthetic pigments embedded in a thylakoid membrane of a chloroplast that absorbs light energy.

Electron Transport Chain

A series of progressively stronger electron acceptors; each time an electron is transferred, energy is released.

Photolysis

A chemical reaction in which a compound is broken down by light.

Oxidation

A reaction in which an atom or molecule loses electrons.

Reduction

A reaction which an atom or molecule gains electrons.

Chemiosmosis

A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.

Photosynthesis Equation

6CO2 + 6H2O + Energy -> C6H12O6 + 6O2

Formula for Glucose

C6H12O6

Chemical Bonds

Where energy is stored in photosynthetic organisms.

Short wavelengths have...

High Energy.

Number of molecules used in the Calvin Cycle?

6 Molecules.

Raw Materials in photosynthesis?

Carbon dioxide and Water.

Molecule of immediate energy?

ATP.

What are the products of 'Light-Dependent' reactions?

ATP, NADPH and O2.

Oxidation

Process in which an atom, ion, or molecule loses electrons, resulting in an increase in its oxidation state.

What does chlorophyll do to green pigment?

Chlorophyll is the green pigment found in plants. It absorbs sunlight during photosynthesis, converting it into chemical energy. This energy is used to produce glucose, which fuels plant growth and development. Chlorophyll plays a crucial role in capturing light energy and is responsible for the green color of leaves.

Where does the Calvin Cycle occur?

The Stroma

Electron Transport Chain

Process in cellular respiration where electrons from NADH and FADH2 are transferred along a series of protein complexes embedded in the inner mitochondrial membrane. This generates a proton gradient, which drives ATP synthesis.

What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
A) anabolic pathways
B) catabolic pathways
C) fermentation pathways
D) thermodynamic pathways
E) bioenergetic pathways

b

The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
A) gains electrons and gains potential energy.
B) loses electrons and loses potential energy.
C) gains electrons and loses potential energy.
D) loses electrons and gains potential energy.
E) neither gains nor loses electrons, but gains or loses potential energy.

b

When electrons move closer to a more electronegative atom, what happens?
A) The more electronegative atom is reduced, and energy is released.
B) The more electronegative atom is reduced, and energy is consumed.
C) The more electronegative atom is oxidized, and energy is consumed.
D) The more electronegative atom is oxidized, and energy is released.
E) The more electronegative atom is reduced, and entropy decreases.

a

Why does the oxidation of organic compounds by molecular oxygen to produce CO₂ and water release free energy?
A) The covalent bonds in organic molecules and molecular oxygen have more kinetic energy than the covalent bonds in water and carbon dioxide.
B) Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).
C) The oxidation of organic compounds can be used to make ATP.
D) The electrons have a higher potential energy when associated with water and CO₂ than they do in organic compounds.
E) The covalent bond in O₂ is unstable and easily broken by electrons from organic molecules.

b

Which of the following statements describes the results of this reaction?
C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy
A) C₆H₁₂O₆ is oxidized and O₂ is reduced.
B) O₂ is oxidized and H₂O is reduced.
C) CO₂ is reduced and O₂ is oxidized.
D) C₆H₁₂O₆ is reduced and CO₂ is oxidized.
E) O₂ is reduced and CO₂ is oxidized.

a

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes
A) hydrolyzed.
B) hydrogenated.
C) oxidized.
D) reduced.
E) an oxidizing agent.

c

When a molecule of NAD⁺ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes
A) dehydrogenated.
B) oxidized.
C) reduced.
D) redoxed.
E) hydrolyzed.

c

Which of the following statements describes NAD⁺?
A) NAD⁺ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
B) NAD⁺ has more chemical energy than NADH.
C) NAD⁺ is oxidized by the action of hydrogenases.
D) NAD⁺ can donate electrons for use in oxidative phosphorylation.
E) In the absence of NAD⁺, glycolysis can still function.

a

Where does glycolysis take place in eukaryotic cells?
A) mitochondrial matrix
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) cytosol

w

The ATP made during glycolysis is generated by
A) substrate-level phosphorylation.
B) electron transport.
C) photophosphorylation.
D) chemiosmosis.
E) oxidation of NADH to NAD⁺.

a

The oxygen consumed during cellular respiration is involved directly in which process or event?
A) glycolysis
B) accepting electrons at the end of the electron transport chain
C) the citric acid cycle
D) the oxidation of pyruvate to acetyl CoA
E) the phosphorylation of ADP to form ATP

b

Which process in eukaryotic cells will proceed normally whether oxygen (O₂) is present or absent?
A) electron transport
B) glycolysis
C) the citric acid cycle
D) oxidative phosphorylation
E) chemiosmosis

b

An electron loses potential energy when it
A) shifts to a less electronegative atom.
B) shifts to a more electronegative atom.
C) increases its kinetic energy.
D) increases its activity as an oxidizing agent.
E) moves further away from the nucleus of the atom.

b

Why are carbohydrates and fats considered high energy foods?
A) They have a lot of oxygen atoms.
B) They have no nitrogen in their makeup.
C) They can have very long carbon skeletons.
D) They have a lot of electrons associated with hydrogen.
E) They are easily reduced.

d

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
A) 0%
B) 2%
C) 10%
D) 38%
E) 100%

e

During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is
A) transferred to ADP, forming ATP.
B) transferred directly to ATP.
C) retained in the two pyruvates.
D) stored in the NADH produced.
E) used to phosphorylate fructose to form fructose 6-phosphate.

c

The free energy for the oxidation of glucose to CO₂ and water is -686 kcal/mol and the free energy for the reduction of NAD⁺ to NADH is +53 kcal/mol. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?
A) Most of the free energy available from the oxidation of glucose is used in the production of ATP in glycolysis.
B) Glycolysis is a very inefficient reaction, with much of the energy of glucose released as heat.
C) Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.
D) There is no CO₂ or water produced as products of glycolysis.

c

In addition to ATP, what are the end products of glycolysis?
A) CO₂ and H₂O
B) CO₂ and pyruvate
C) NADH and pyruvate
D) CO₂ and NADH
E) H₂O, FADH₂, and citrate

c

Starting with one molecule of glucose, the energy-containing products of glycolysis are
A) 2 NAD⁺, 2 pyruvate, and 2 ATP.
B) 2 NADH, 2 pyruvate, and 2 ATP.
C) 2 FADH₂, 2 pyruvate, and 4 ATP.
D) 6 CO₂, 2 ATP, and 2 pyruvate.
E) 6 CO₂, 30 ATP, and 2 pyruvate.

b

In glycolysis, for each molecule of glucose oxidized to pyruvate
A) two molecules of ATP are used and two molecules of ATP are produced.
B) two molecules of ATP are used and four molecules of ATP are produced.
C) four molecules of ATP are used and two molecules of ATP are produced.
D) two molecules of ATP are used and six molecules of ATP are produced.
E) six molecules of ATP are used and six molecules of ATP are produced.

b

A molecule that is phosphorylated
A) has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.
B) has a decreased chemical reactivity; it is less likely to provide energy for cellular work.
C) has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate.
D) has an increased chemical potential energy; it is primed to do cellular work.
E) has less energy than before its phosphorylation and therefore less energy for cellular work

d

Why is glycolysis described as having an investment phase and a payoff phase?
A) It both splits molecules and assembles molecules.
B) It attaches and detaches phosphate groups.
C) It uses glucose and generates pyruvate.
D) It shifts molecules from cytosol to mitochondrion.
E) It uses stored ATP and then forms a net increase in ATP

e

Which kind of metabolic poison would most directly interfere with glycolysis?
A) an agent that reacts with oxygen and depletes its concentration in the cell
B) an agent that binds to pyruvate and inactivates it
C) an agent that closely mimics the structure of glucose but is not metabolized
D) an agent that reacts with NADH and oxidizes it to NAD⁺
E) an agent that blocks the passage of electrons along the electron transport chain

c

The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion?
A) active transport
B) diffusion
C) facilitated diffusion
D) through a channel
E) through a pore

a

Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO₂) from one molecule of pyruvate?
A) lactate
B) glyceraldehydes-3-phosphate
C) oxaloacetate
D) acetyl CoA
E) citrate

d

During cellular respiration, acetyl CoA accumulates in which location?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix

e

How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
A) two
B) four
C) six
D) eight
E) ten

a

Carbon dioxide (CO₂) is released during which of the following stages of cellular respiration?
A) glycolysis and the oxidation of pyruvate to acetyl CoA
B) oxidation of pyruvate to acetyl CoA and the citric acid cycle
C) the citric acid cycle and oxidative phosphorylation
D) oxidative phosphorylation and fermentation
E) fermentation and glycolysis

b

A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal hospital for some tests. There they discover his mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of his condition?
A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
B) His cells cannot move NADH from glycolysis into the mitochondria.
C) His cells contain something that inhibits oxygen use in his mitochondria.
D) His cells lack the enzyme in glycolysis that forms pyruvate.

a

During aerobic respiration, electrons travel downhill in which sequence?
A) food → citric acid cycle → ATP → NAD⁺
B) food → NADH → electron transport chain → oxygen
C) glucose → pyruvate → ATP → oxygen
D) glucose → ATP → electron transport chain → NADH
E) food → glycolysis → citric acid cycle → NADH → ATP

b

What fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle, if glucose is the sole energy source?
A) 1/6
B) 1/3
C) 1/2
D) 2/3
E) 100/100

d