exam 2 cell bio

Although the path of one glucose molecule through glycolysis generates a total of four ATP molecules, there is a net gain of only two ATP for each glucose molecule that enters the pathway. Why does the passage of one glucose molecule through glycolysis have a payoff of only two ATP molecules?

Two ATP molecules are used in the initial phase of glycolysis, reducing the net gain to two ATP.

Which of the following is a simplified equation for cellular respiration?

Glucose + oxygen -----> carbon dioxide + water

cytosol

breakdown of glucose to pyruvate

During one of the three phases of the Calvin cycle, the carbon atoms from three CO2 molecules are incorporated into three five-carbon sugar molecules called ribulose bisphosphate (RuBP). This reaction forms an unstable six-carbon intermediate which immediately splits into two three-carbon sugar molecules called 3-phosphoglyceric acid (3PGA). In which phase of the Calvin cycle does this occur?

carbon fixation

What is the function of the enzyme rubisco?

catalyzes the fixation of carbon dioxide to ribulose bisphosphate during the Calvin cycle

Which statement best defines pheromones?

chemicals released by organisms to convey information with members of their own species

mitochondrial matrix

citric acid cycle

mitochondrial membrane

conversion of pyruvate to acetyl-CoA

Which of the following eukaryotic cell parts is found in the cytoplasm, enables cell movement, and is composed of interconnected protein fibers?

cytoskeleton

mitochondrial matrix

electron transport chain

Nearly all eukaryotic cells contain a class of small, round organelles that contain oxidative enzymes. The enzymes break down organic substances via oxidation reactions. What are these organelles called?

peroxisomes

. Cellular respiration consumes glucose during glycolysis. What product of glycolysis can be subsequently modified to enter the citric acid cycle under aerobic conditions?

pyruvate

During one of the three phases of the Calvin cycle, six molecules of ATP and six molecules of NADPH transfer electrons to six three-carbon sugars known as 3-phosphoglyceric acid (3PGA). The transfer of electrons transforms the six 3PGA molecules into six molecules of a three-carbon sugar called glyceraldehyde-3-phosphate (G3P). In which phase of the Calvin cycle does this occur?

reduction

During one of the three phases of the Calvin cycle, three molecules of ATP are used to catalyze the rearrangement of five three-carbon sugars, known as glyceraldehyde-3-phosphate (G3P), into three five-carbon sugars, known as ribulose bisphosphate (RuBP). One other molecule of G3P is exported to the cytoplasm to form glucose. In which phase of the Calvin cycle does this occur?

regeneration

How does a signaling molecule present in low concentrations cause a significant response in the cell?

signal amplification

Small molecules and proteins can act as cellular communication signals by binding to cell receptors. A protein binds to its receptor on a cell surface and starts a biochemical chain reaction within the cell. What is the general term for this type of pathway?

signal transduction

What is the role of second messengers in signal-transduction pathways?

small molecules or ions that relay a signal from the cell's surface to the cell's interior

ATP

the direct energy source for glycolysis

What is visible light?

the wavelengths of electromagnetic radiation living organisms most often use

How can cells of different tissues respond differently to the same signal molecule?

variations in the set of proteins that the cell possesses

Why do most plant leaves appear green?

Pigments in plant cells absorb blue and red light, but much of the green light is reflected.

Assume that one molecule of glucose enters glycolysis and that all of its metabolites are used in generating adenosine triphosphate (ATP) by cellular respiration. What percentage of ATP generated in cellular respiration is produced directly by the reactions of glycolysis?

less than 15%

Osmosis is the movement of water across a semipermeable membrane from a region of low to high solute concentration. Considering the definition of osmosis, which of the following statements describe chemiosmosis?

movement of ions across a semipermeable membrane from a region of high to low ion concentration

Which situations involve a cell using endocytosis?

1. A free-living single-celled organism engulfs a smaller single-celled organism and uses the smaller organism as a food source. 2. A cell wraps a portion of its membrane around a droplet of nutrient-rich water and brings the droplet inside the cell.

Which of the following are examples of cell signaling? Choose all that apply.

1. As a response to increasing densities, bacteria coordinate behaviors and form biofilms. 2. A neuron releases neurotransmitters into a synapse, triggering a target nerve cell. 3. Thyroid hormone stimulates body cells to increase metabolic activity.

Many eukaryotic organisms rely on the processes of photosynthesis and cellular respiration to sustain life. Choose the statements that accurately describe the two processes

1. Both processes are capable of forming ATP for use as an energy source. 2. Carbon dioxide is a reactant in one process and a product in the other process. 3. Mitochondria participate in one process and chloroplasts participate in the other.

In what ways does photosynthesis in C4 plants differ from photosynthesis in C3 plants?

1. C4 plants can continue to make sugars on hot, dry days when the stomata are closed. 2. C4 plants do not produce sugars as efficiently as C3 plants during cool, wet conditions. 3. C4 plants use one set of cells to fix carbon and another set of cells to produce sugars.

Exocytosis is a type of cellular transport that allows materials to move across the plasma membrane of a cell. Which of the statements describe properties of exocytosis?

1. Exocytosis is the primary method of transporting large molecules out of the cell. 2. Exocytosis secretes materials from the cell through the fusion of a vesicle with the plasma membrane.

Select all of the correct statements about the extracellular matrix found in animals.

1. Its functions include holding cells together in tissues. 2. It contains water and a network of proteins and can be flexible.

Select all the choices that correctly describe the Golgi apparatus of the cell.

1. Proteins are modified by this organelle and repackaged into transport vesicles. 2. This organelle is part of the endomembrane system.

Which of the following are mechanisms that a cell uses to relay an external signal during signal transduction?

1. Second messengers 2. Protein phosphorylation

Ligands bind reversibly to their receptors. Select the statements that describe what would happen if ligands bound irreversibly with their receptors.

1. The cell cannot receive new signals. 2. Termination of the signal cannot occur.

Select the descriptions that apply to the thylakoid.

1. The thylakoid membrane is the site of the light-dependent reactions of photosynthesis. 2. The thylakoid membrane is the site of an electron transport chain that generates cellular energy from light energy. 3. Thylakoids are arranged within the chloroplast into stacks of coin-shaped discs called grana.

Select the descriptions that apply to the ribosome.

1. a molecular structure that is the site of protein synthesis 2. a cellular structure that is composed of both RNA and protein

Microtubules filaments (microfilaments)

1. are composed of tubulin subunits 2. make up the core of cilia and flagella 3. maintain cell shape by resisting compression

Which statements describe characteristics of stomata in plants?

1. are openings into a plant that are surrounded by guard cells 2. allow gases, such as CO2 and O2, to enter and escape from a plant

What are the functions of the cell wall in plants?

1. contains plasmodesmata that allow nutrients to enter the cell 2. provides rigidity to the plant and determines cell shape 3. provides protection from a variety of different pathogens

Intermediate filaments

1. fix certain organelles in place 2. are not involved in cell motility

Actin filaments

1. function in muscle contraction 2. play a role in cleavage furrow formation during cell division

Select the phrases that complete the following sentence. The mitochondrion

1. has a double membrane, with ATP synthesis occurring at the inner membrane. 2. contains unique DNA that is different from the cell's nuclear DNA

Which of the following are types of motor proteins?

1. myosin 2. kinesin

Plants synthesize their own food in the form of sugars during the process of photosynthesis. Which of the following statements describe photosynthesis?

1. produces sugars for the plant using the energy from sunlight 2. is a cellular process that occurs in the chloroplasts of plant cells 3. cannot convert sunlight energy to sugars without the direct input of carbon dioxide

Which of the following correctly describe vacuoles? Choose all the statements that apply.

1.can break down macromolecules 2. membrane-bound organelle 3. has little or no internal structure

During glycolysis, glucose is broken down into two molecules of pyruvic acid. How many carbon atoms are in each pyruvic acid molecule?

3 carbon atoms

Pyruvate is a product of glycolysis and is subsequently converted to acetyl-CoA. Acetyl-CoA is a substrate for the citric acid cycle (CAC). Exactly how many molecules of glucose must be oxidized in glycolysis to provide the input for 12 turns of the CAC?

6

At any given time, there is an array of signaling molecules in a cell's environment. How does a cell "know" which signaling molecules to respond to?

A cell responds to a signaling molecule only if the cell has the appropriate receptor.

How do chlorophyll pigments absorb energy from light?

A photon excites an electron in the chlorophyll to a higher energy state

desmosomes

Act as rivets to hold adjacent cells together when epithelial tissue moves

plasmodesmata

Allow passage of materials through the cell walls of adjacent plant cells

Anaerobic respiration allows a cell to break down carbohydrates in the absence of oxygen. Identify how NAD+ is used by animal cells during anaerobic respiration.

Glycolysis requires NAD+ produced from fermentation to produce ATP.

Consider what happens to energy in photosynthesis. How does this differ from what happens to energy in cellular respiration?

In photosynthesis, energy is captured from light, whereas in cellular respiration energy is transferred from storage molecules to ATP.

How do the nucleus and ribosomes work together to generate a protein?

In the nucleus, DNA is transcribed to mRNA, which the ribosomes use as instructions to synthesize a specific protein.

The electron transport chain consists of protein complexes embedded in the inner mitochondrial membrane, where it generates a proton gradient by a series of oxidation-reduction, or redox, reactions. Although all the stages of cellular respiration (glycolysis, the citric acid cycle, and the electron transport chain) are necessary for life, the electron transport chain is sometimes called the most important stage. First complete the sentence, then answer the question below. The electron transport chain uses the transfer of electrons between protein complexes to set up a proton gradient. What is the function of the proton gradient in the mitochondrion?

It is potential energy that the cell uses to generate ATP.

tight junctions

Prevent liquid from seeping between cells

gap junctions

Small, protein-lined channels connecting adjacent animal cells

grana

Stacks of thylakoids

Which of the following scenarios is a direct effect of the absence of carbon dioxide during photosynthesis?

The carbon fixation stage of the Calvin cycle would be unable to synthesize the sugar 3-PGA.

glucose

a carbohydrate that enters glycolysis directly

Which of the following is the definition of a cell junction?

a connection between adjacent cells or between a cell and the extracellular matrix

ATP

a product that can be used directly for energy

NADH

a product that donates electrons to the electron transport chain

matrix

a semi-fluid space enclosed by an inner membrane that contains DNA, ribosomes, and enzymes used in the citric acid cycle

Select the best description of collagen from the list below.

an abundant fibrous glycoprotein found in the extracellular matrix of tissues

pyruvic acid

an end product that is modified to enter the citric acid cycle

thylakoid

an oval sac with chlorophyll contained within its membrane.

In eukaryotic cells, each stage of cellular metabolism generates a different net amount of ATP. Which stage directly generates the greatest number of ATP molecules per metabolized glucose molecule?

electron transport chain and ATP synthase

stroma

fluid located within an inner membrane that contains DNA, ribosomes, and grana used in photosynthesis.

cristae

folds in an inner membrane that contain proteins used in ATP synthesis

A proton gradient is formed in the mitochondria such that the concentration of protons (H ) is higher on one side of the inner mitochondrial membrane than on the other side. What is the purpose of this proton gradient?

generates ATP in the electron transport chain