Exam 2 Sapling

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.

contrast anabolic and catabolic pathways?

Anabolic pathways are synthesis pathways, whereas catabolic pathways are degradation pathways.

a product that can be used directly for energy

ATP

the direct energy source for glycolysis

ATP

In general, what happens during an oxidation-reduction reaction between two molecules?

An atom in the reduced molecule attracts an electron that an atom in the oxidized molecule donates.

What does the second law of thermodynamics state about energy?

Given the opportunity, energy disperses away from a concentrated source into places with less energy.

What does the first law of thermodynamics state about energy?

Energy can be transformed, but it cannot be either created or destroyed.

What is the primary difference between prokaryotic and eukaryotic cells?

Eukaryotic cells have membrane-bound compartments called organelles, whereas prokaryotic cells do not.

what occurs during the light-dependent reactions of photosynthesis?

Excited electrons help move H ions to create a concentration gradient. H ions are used to help produce the energy carriers, ATP and NADPH. Electrons on special chlorophyll molecules gain energy from light.

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.

What does the fluid mosaic model describe about the structure of plasma membranes?

Proteins and other membrane components are embedded in the membrane. Phospholipids in the membrane are not covalently bonded to each other.

describe rough ER

It produces proteins that need to be modified before use. It has ribosomes bound to its membrane. It is connected to the membrane of the nucleus.

Which of the following statements about lysosomes are true? Select all that apply. Lysosomes are responsible for programmed cell death. Lysosomes neutralize toxic peroxide wastes. Lysosomes are membrane spheres containing digestive enzymes. Lysosomes break down damaged organelles for recycling.

Lysosomes are responsible for programmed cell death. Lysosomes are membrane spheres containing digestive enzymes. Lysosomes break down damaged organelles for recycling.

What happens in the transduction phase of cell signaling when protein signal molecules are present?

Signal molecules induce a change in membrane proteins that activates other proteins within the cell.

Which products of photosynthesis are used for cellular respiration?

O2 & carbohydrates

describe the thylakoid

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

Which statement describes the function of photosynthetic pigments in leaves?

They absorb light energy and trap high energy electrons.

describe golgi apparatus

This organelle is made up of flattened sacs of membrane. Proteins are modified by this organelle and repackaged into transport vesicles.

How do enzymes recognize their substrates?

a binding site that fits the shape and complements the charge of the substrate

The cells that make up multicellular organims send, receive, and respond to a variety of signals. Endocrine signaling is a form of cell-to-cell communication in which...

a cell produces a signal released into the bloodstream to be carried to specific distant organ.

The cells that make up multicellular organims send, receive, and respond to a variety of signals. Paracrine signaling is a form of cell-to-cell communication in which...

a cell produces a signal that induces changes in local, nearby, cells.

What is the proton gradient in cellular respiration?

a difference in the concentration of protons (H ) on either side of a membrane

entropy is _______

a measure of the disorder or energy dispersal in a system

describe a chloroplast

a membrane-bound organelle that contains chlorophyll the main site of photosynthesis in a plant cell

describe the fluid mosaic model

a phospholipid bilayer with various molecules embedded within and floating between the layers

describe endergonic reaction

a reaction that requires energy to be completed

matrix

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

describe a ligand

a small molecule that binds to a protein and affects the protein's function

describe smooth ER

an organelle that synthesizes fatty acids, phospholipids, and steroids a membranous structure that surrounds the nucleus without attached ribosomes

thylakoid

an oval sac with chlorophyll contained within its membrane

describe protein kinase

binds ATP phosphorylates a protein

Which of the following is an organelle, is characterized by stacked, disc shaped structures, and converts energy from the sun into usable sugars for plants?

chloroplast

the mitochondrion ___________

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

describe calvin cycle

converts CO2 to simple sugars, does not directly use sunlight energy, occurs in stroma of chloroplast

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

ethanol fermentation

generates ethanol used by yeast cells considered to be an anaerobic process regenerates NAD+ that can be used in glycolysis

a carbohydrate that enters glycolysis directly

glucose

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

glucose + oxygen -> CO2 + H20

which steps in cellular respiration generate NADH or FADH2?

glycolysis citric acid cycle acetyl CoA production

list stages of cellular respiration in order from first to last

glycolysis conversion of pyruvate to acetyl-CoA citric acid cycle electron transport chain

What are some characteristics of an exergonic reaction?

has negative free energy spontaneous releases energy

describe photosynthesis

is a cellular process that occurs in the chloroplasts of plant cells converts carbon dioxide to sugars, releasing oxygen generates sugars from the energy contained in sunlight

Activation energy is best defined as the energy that

is required to bring the reactant molecules to a transition state.

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%; most come from oxidative phosphorylation

What provides the energy that excites the electrons in the chlorophyll molecules?

light

Which cellular component is a membrane-bound organelle that digests nutrients and cellular waste?

lysosome

Identify which of the following are traits of mitochondria, chloroplasts, or both organelles.

mitochondria: contains folded inner membrane, found in cells of animals, converts glucose to ATP chloroplasts: converts solar energy into food, filled with thylakoid stacks both: found in cells of plants, has separate set of DNA

Which organelle has a smooth outer membrane, an extensively folder inner membrane, and is the site of ATP production in eukaryotic cells?

mitochondrion

which steps in cellular respiration receive NADH or FADH2?

oxidative phosphorylation

describe some aspects of glycolysis

produces 2 ATP and 2 NADH common to aerobic and anaerobic respiration

lactic acid fermentation

produces lactic acid (lactate) used by animal cells considered to be an anaerobic process regenerates NAD+ that can be used in glycolysis

What are mechanisms that a cell uses to relay an external signal during signal transduction?

protein phosphorylation & 2nd messengers

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

pyruvate

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

pyruvic acid

describe diffusion

The movement of a substance down a concentration gradient from an area of high concentration to an area of low concentration.

Which of the following describes the way in which phosphorylation directly contributes to signal transduction?

Addition of phosphate groups alters the three-dimensional protein structure, which allows the protein to interact with new binding partners.

a product that donates electrons to the electron transport chain

NADH

Facilitated diffusion is a type of passive transport that allows solutes to move across the plasma membrane of a cell. Which statements describe facilitated diffusion?

Small, charged molecules and ions move down their concentration gradient out of a cell through proteins in the plasma membrane. Solutes move across the membrane down their concentration gradient through specialized membrane proteins.

What happens in the reception phase of cell signaling when protein signal molecules are present?

Specialized cell surface proteins bind to specific protein signal molecules outside the cell.

Which statement accurately describes the Calvin cycle?

The Calvin cycle is a light-independent metabolic pathway occurring in the chloroplast stroma that converts carbon from carbon dioxide into sugar.

How does adenosine triphosphate (ATP) drive energy-required reactions in the cell?

The hydrolysis of ATP is coupled to a non-spontaneous reaction.

Phospholipids have the ability to spontaneously form complex structures such as lipid bilayers. What is a property of phospholipids that explains why lipids self-assemble into a bilayer?

The hydrophobic tails of lipids are buried in the membrane and are pointed toward each other.

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.

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

Which of the following is a function of cholesterol in a cell\'s plasma membrane?

regulating membrane fluidity

describe protein phosphatase

removes phosphate group from protein releases inorganic phosphate

Some ribosomes are used to make proteins, such as insulin, that will be modified and sent out of the cell. Where in the cell are these ribosomes most likely found?

rough ER

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 transmit a signal from the exterior of the cell to the interior of a cell

Which centrally located organelle produces lipids, detoxifies drugs in the liver, and is composed of a membrane network?

smooth ER

grana

stacks of thylakoids

describe electrochemical gradient

sum of the differences in charge and chemical concentration of ions across a membrane

describe kinetic energy

the energy an object has as a result of its own movement

What is free energy (G)?

the energy available to perform work

describe free energy

the energy from a reaction that is available to do work

what is the site for light dependent reactions

thylakoid

You have been hired to develop a drug to inhibit the action of a certain enzyme. Where should the drug bind to competitively inhibit the enzyme?

to the active site of the enzyme

What provides nonwoody plants with the support they need to stand erect?

turgor pressure

What is the source of the electrons that replace the excited electrons lost from chlorophyll?

water

Which molecules are reactants in photosynthesis in plants?

water & CO2

What is produced during photosynthesis in plants?

water & carbs