Biology

A simplified overall equation for respiration is as follows: C6H12O6 + 6O2 →6CO2+ 6H2O + energy In this reaction, we can say that _____ is reduced and _____ is oxidized.

oxygen; glucose

A protein that is temporarily associated with a biological membrane is a(n):

peripheral membrane protein.

Which process produces the highest number of reduced electron carriers and thus the greatest potential for generating ATP?

the citric acid cycle

The energy of activation of a reaction is:

the energy input needed to reach the transition state.

Of the 6 carbons in a starting molecule of glucose, at the completion of pyruvate oxidation, _____ carbons are fully oxidized to _____, while _____ carbons remain in _____.

two; CO2; four; acetyl groups

Tracing the metabolism of one glucose molecule, how many carbon atoms are available for further oxidation at the completion of the pyruvate oxidation stage?

4

Which of the following is required for the preparatory phase of glycolysis and then produced during the payoff phase?

ATP

Which of the following is the most common energy "currency" for a cell?

ATP

The immediate source of electrons for the electron transport chain is:

NADH and FADH2.

Which of the statements are true? Select all that apply.

The amount of usable energy resulting from a reaction is always less than the total energy available at the start of the reaction. The energy for a reaction equals the sum of the energy in the product plus energy released as heat and disorder.

A biologist working in a lab adds a compound to a solution that contains an enzyme and substrate. This particular compound binds reversibly to the enzyme at the active site. Once the compound is bound to the enzyme, the catalysis of substrate to product stops. Which of the statements is true of the compound?

The effect of the compound can be overcome by adding more substrate.

Imagine that several atoms bond to form a carbohydrate, creating a more orderly system. Which statement is true regarding the universe after this carbohydrate forms?

The entropy of the universe increases.

substrate-level phosphorylation

The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.

Active binding site

The part of G-actin that forms a cross-bridge with the myosin head

active site

The part of an enzyme or antibody where the chemical reaction occurs.

first law of thermodynamics

The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.

allosteric inhibition

The process in which an enzyme's activity is changed because of binding to the allosteric site.

oxydative phosphorylation

The production of ATP as a result of energy released by the Electron Transport System.

Based on the two-step model of glucose transport, what would happen if the rate of function of the sodium-potassium pump increased?

The sodium-potassium pump would make a stronger sodium gradient, so more glucose could be transported across the membrane.

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations of salt (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. The salt and water will move through the membrane by diffusion. Which statement is true about the diffusion of these solutions?

There will be a net movement of salt from side B to side A and net movement of water from side A to side B.

Hydrophobic

Water fearing

Which choice is considered an integral membrane protein?

a protein with its amino-terminus in the cytoplasm and its carboxy-terminus in the extracellular space

Where does the F1 subunit of ATP synthase get its energy to catalyze the synthesis of ATP?

from rotational energy provided by the flow of protons through the channel in the Fo subunit

In cellular respiration, oxygen:

gains electrons and is reduced

In cellular respiration, oxygen:

gains electrons and is reduced.

All cells have:

genetic information

Which molecule has the greatest chemical potential energy?

glucose

Which of the following are inputs, but not outputs, of glycolysis?

glucose

Excess glucose is stored in large branched molecules of:

glycogen in animals.

How did the earliest organisms on Earth most likely produce ATP?

glycolysis

Based on what you know of ATP's chemistry, which of the substances is most likely to have similar functions in energy-management processes?

guanosine nucleotide triphosphate

The outer surface of the Fo subunit of ATP synthase must be _____ to be embedded in the membrane.

hydrophobic

Which has the most entropy, individual nucleotides or a nucleic acid?

individual nucleotides

ATP is a good energy currency for cells because it has a(n) _____ amount of Gibbs free energy.

intermediate

The breakdown of fatty acids takes place by a process called:

beta-oxidation.

Carbohydrates

can also be found in cell membranes, usually attached to lipids (glycolipids) and proteins (glycoproteins).

Imagine that you discover a microbial deep-sea organism that can derive energy from (inorganic) hydrogen gas (H2). In addition, this microbe can synthesize organic compounds from carbon-containing inorganic molecules in the ocean. This microbe is a:

chemoautotroph

Imagine that you discover a carnivorous deep-sea fish that cannot utilize the carbon in carbonic acid, or any other inorganic molecule, present in seawater to form glucose, or other organic molecules. Living so far beneath the water's surface, this fish is also incapable of harnessing energy from the sun. This fish would be considered a:

chemoheterotroph.

Animals such as cats, worms, and butterflies are classified as:

chemoheterotrophs

Escherichia coli bacteria in your colon are categorized as:

chemoheterotrophs.

Which of the following is a pigment associated with chloroplasts that plays a role in energy harvesting?

chlorophyll

What would be found in the cells of a blade of grass but not in the cells of an insect feeding on that grass?

chloroplasts

A research group has discovered an organism with cells that contain a previously undescribed organelle. Researchers perform some tests on the isolated organelle to see if it is involved in any major metabolic reactions. To do this, they incubate these organelles for a period of time and determine changes in the amount of various substances in the suspending solution. The results are shown in the table.

citric acid cycle

Metal ions bound to enzymes are called:

cofactors

The first law of thermodynamics is also known as the law of:

conservation of energy.

An amphipathic molecule is one that:

contains both polar and nonpolar regions.

In eukaryotes, fermentation takes place:

cytoplasm

In eukaryotic cells, glycolysis occurs in:

cytoplasm

Phototrophs

"plants" feed themselves with light.

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

Tracing the metabolism of one glucose molecule, how many carbon atoms are fully oxidized to CO2 at the completion of glycolysis?

0

Translation of a protein destined to function in the nucleus occurs:

on free ribosomes in the cytosol.

Which choice correctly lists the approximate number of ATP produced by (1) metabolism of a 16-carbon fatty acid, (2) fermentation of a single glucose, and (3) aerobic respiration of a single glucose, in that order? For this calculation, you will need to know that each 2-carbon unit cleaved from the fatty acid yields one NADH and one FADH2, and the 2-carbon unit is added to coenzyme A to become acetyl-CoA, which is further metabolized by the citric acid cycle.

108, 2, 32

Which of the following is a net product of glycolysis?

2 pyruvate

Starting from glucose, lactic acid fermentation results in _____ molecules of lactic acid, each with _____ carbons, whereas ethanol fermentation results in _____ molecules of ethanol, each with _____ carbons.

2; 3; 2; 2

As a cat pounces on a mouse, its muscles consume 10 units of potential energy (which the cat previously gained from the food it consumed). However, the pounce itself only required 4 units of kinetic energy. How many units of energy were dissipated as heat?

6

Tracing the metabolism of one glucose molecule, how many carbon atoms are fully oxidized to CO2 at the completion of aerobic respiration?

6

The diagram shown represents the four stages of aerobic cellular respiration as four simple boxes. Many of the "inputs" and "outputs" are shown as arrows. Open arrows represent "energy management molecules" (ATP and electron carriers), and closed arrows represent other inputs and outputs, such as substrates and products. Use this diagram to answer the question.

A

hydrolysis reaction

A chemical reaction that breaks apart a larger molecule by adding a molecule of water

Endergonic

A chemical reaction that requires the input of energy in order to proceed.

negative feedback

A primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation.

Catabolic

A process in which large molecules are broken down -> Makes ATP

Anabolic

A process in which large molecules are built from small molecules -> require ATP

During the citric acid cycle:

ATP is synthesized by substrate-level phosphorylation.

Which statement is true about the presence or absence of plasma membranes?

All cells have a plasma membrane.

Chemoheterotrophs

An organism that must consume organic molecules for both energy and carbon.

Photoheterotrophs

An organism that obtains energy from sunlight and carbon from organic sources.

Scientists use which of the following as evidence that mitochondria and chloroplasts had prokaryotic origins?

Both contain their own circular DNA.

Which of these reactions summarizes the overall reactions of cellular respiration?

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

Some bacteria run the citric acid cycle in reverse. Without any other modifications to the cycle, what inputs would be required to do this?

CO2, FADH2, NADH, and ATP

Exergonic

Chemical reactions that release energy

We consume a variety of carbohydrates that are digested into a variety of different monosaccharides. How do these different sugars enter glycolysis?

Different sugars can be modified to form different intermediates of glycolysis.

Imagine a cell that has a membrane composed mostly of lipids with saturated fatty acid tails, and that this membrane also has low cholesterol content. What are the characteristics of this cell membrane?

Due to its low cholesterol content, the cell membrane would lose its fluidity at cold temperatures.

Cells (requirements)

ENERGY A way to encode/transmit information A membrane separating the inside of the cell from the outside

potential energy

Energy that is stored and held in readiness

You are talking with one of your friends. He states that evolution has actually violated the second law of thermodynamics, because complex living organisms are more ordered than the nucleic acids, amino acids, and other molecules that compose them. Why doesn't evolution contradict the second law of thermodynamics?

Even though evolution may decrease the entropy of living organisms, it increases the entropy of the Earth (or the universe), as the chemical reactions that are required to make organisms release heat.

Which statement is true about exergonic reactions?

Exergonic reactions are catabolic.

energetic coupling

In cellular metabolism, the mechanism by which energy released from an exergonic reaction (commonly, hydrolysis of ATP) is used to drive an endergonic reaction.

A researcher has devised a technique that allows her to label all the integral membrane proteins with a fluorescent tag. She uses a laser to bleach the fluorescence in a specific area of the cell membrane. After 24 hours, she notices that fluorescence has returned to the bleached area. What can she deduce from this experiment?

Integral membrane proteins are able to move laterally within the cell membrane.

Why is the energy from a molecule of ATP required by the sodium-potassium pump?

It provides the energy required to move sodium and potassium ions against their concentration gradients.

The coronary arteries supply oxygenated blood to heart muscle. Following a heart attack, which of the events would occur in heart tissue due to a block in the coronary arteries? Select all that apply.

Lactic acid would accumulate in the tissue due to glycolysis and fermentation. Phosphofructokinase, an intermediary enzyme of glycolysis, would be activated. The production of ATP would decrease.

How can lysosomal enzymes that work best at a pH of 5 be fully functional if the pH of the cytoplasm is 7?

Lysosomal enzymes are separated from the cytoplasm by the membrane surrounding the lysosome.

Chemautotrophs

Obtain energy directly from chemical reactions

Phosphofructokinase is an allosteric enzyme in the pathway that breaks down glucose to produce ATP. Regulation of glycolysis is directly related to the level of ATP and citrate. If ATP or citrate levels are high, phosphofructokinase is inhibited. What will happen to this enzyme when ATP levels drop?

Phosphofructokinase is activated.

Researchers seldom find prokaryotic cells that are greater than 100 micrometers in diameter. Why would the size of prokaryotic cells be restricted?

Prokaryotic cells must absorb all of their nutrients from their environment and therefore require a high surface area to volume ratio.

Which statement is true regarding pyruvate oxidation?

Pyruvate oxidation forms the same number of NADH (per glucose molecule) as glycolysis.

Which of the statements represent the laws of thermodynamics? Select all that apply.

The amount of energy in the universe is constant. The energy available to do work decreases as energy is transformed from one form to another

During translation, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal sequences. Which peptides would you expect to find in the polypeptide that will eventually fold to become an ion channel protein? Select all that apply.

a signal-anchor peptide an amino-terminal signal peptide

Glycolysis is a series of chemical reactions (endergonic and exergonic) by which the cell can obtain ATP. NAD+ plays a crucial role in the reactions of glycolysis by:

accepting electrons during glycolysis, with the overall result that glucose is partially oxidized to pyruvate.

As atmospheric carbon dioxide levels increase, the oceans become more:

acidic

In a reaction, enzymes change the:

activation energy

Of the choices, which can be a product of a catabolic reaction?

an amino acid like tryptophan

The assembly of glucose molecules into polysaccharides is a(n) _____ process.

anabolic

Glycolysis is:

anaerobic

Chematroph

animals

In order for phospholipids to form bilayers spontaneously in an aqueous environment, the pH should be:

approximately neutral.

Cell membranes

are composed of two layers of lipids.

Phospolipids

are made up of a glycerol backbone attached to a phosphate group and two fatty acids

Proteins

are often embedded in or associated with the membrane, where they perform important functions such as transporting molecules.

Lipids

are the main component of cell membranes. They have properties that allow them to form a barrier in an aqueous (watery) environment. Membranes are not, however, made up of only lipids.

metabolic pathway

begins with a specific molecule and ends with a product

Most of the proteins of the electron transport chain are:

embedded in the inner mitochondrial membrane.

kinetic energy

energy of motion

The degree of disorder, or number of microstates, is called:

entrophy

A single molecule is always either hydrophobic or hydrophilic and can never possess (at the same time) a region that is hydrophobic and a region that is hydrophilic.

false

In a metabolic pathway, a series of enzymatic reactions catalyzes the conversion of molecule A to molecule E. Several intermediate steps are involved in which the product of one reaction becomes the substrate for the next. The graph illustrates the changes of free energy that occur at each step in the pathway.

is an anabolic pathway

An avalanche is an example of _____ energy.

kinetic

During pyruvate oxidation, pyruvate is broken down into CO2 and an acetyl group. The CO2 is:

less energetic than the acetyl group

Acetate is the starting point for synthesis of a cell's:

lipids

In which eukaryotic organelle are various macromolecules broken down and destroyed?

lysosome

A cell has a mutation that prevents it from breaking down unwanted proteins present in vesicles. Which cellular structure is most likely to be disrupted by this mutation?

lysosomes

The chemical bonds of carbohydrates and lipids have high potential energy because:

many of these bonds are C—C and C—H bonds, in which electrons are shared equally between atoms.

Entropy

measure of disorder

In which eukaryotic organelle are some macromolecules broken down to obtain useful energy for the cell in the form of ATP?

mitochondria

In eukaryotes, pyruvate oxidation takes place in the:

mitochondrial matrix.

Which organisms are considered heterotrophs?

most bacteria and dogs

Spontaneous reactions have a _____ ΔG.

negative

+ delta G

non-spontaneous; anabolic

RNA molecules are transported from the nucleus to the cytoplasm in eukaryotes through:

nuclear pores.

The genetic material of a prokaryotic cell is located in its:

nucleoid.

ATP is a type of _____ and is composed of adenine, _____, and three phosphate groups.

nucleotide; ribose

All of the following are properties of at least some prokaryotic cells except:

nucleus

Imagine you have radioactively labeled a protein in the lumen of the endoplasmic reticulum. That protein has an amino-terminal signal sequence that binds the SRP and no other signal sequences. Where would you predict the labeled protein will ultimately end up? Refer to the figure shown. Click to view full size.

outside the cell

During the citric acid cycle, the production of CO2 is the result of the _____ of intermediate compounds of the citric acid cycle coupled to the production of _____.

oxidation; NADH

Which lipid composition option has the least membrane fluidity?

phospholipids with long-chain, saturated fatty acids

Oak trees are categorized as:

photoautotrophs

chemical energy

potential energy stored in chemical bonds

Organic molecules store _____energy in their _____ bonds.

potential; covalent

What type of molecule is sometimes found spanning a cell's plasma membrane with part of the molecule on one side of the membrane, part embedded in the membrane, and part on the other side?

protein

Converting glucose to glycogen:

requires energy

In intestinal epithelial cells, a transport protein moves the bulky, polar glucose molecules through the membrane into the cytoplasm, while simultaneously transporting Na+ through the membrane into the cell down its electrochemical gradient. Which example correctly describes this cotransport of glucose and sodium?

secondary active transport by a symporter

Reactions in which there is a negative change in free energy (-ΔG) are:

spontaneous and exergonic.

- Delta G

spontaneously; release energy; catabolic (release energy often ATP)

enzyme inhibitors

substrate imposters that plug up the active site

Which components are parts of the endomembrane system?

the nuclear envelope

Which of the structures are part of the endomembrane system?

the nuclear envelope

Nearly all cells use ATP as their primary energy source. This is evidence that:

the use of ATP by cells evolved early in the history of life and has been conserved over time.

Enthalpy

total energy to do work

In addition to destabilizing glucose for subsequent breakdown, what else does phosphorylation of glucose do?

traps glucose inside the cell

Photo autotrophs

use the energy of light to produce organic molecules (trees, algae)

Which of the following is a product (as opposed to a substrate) of at least one of the processes of cellular respiration?

water

Hydrophilic

water loving

Carbon-carbon covalent bonds, such as the ones in carbohydrates and lipids, are _____ and have _____.

weak; a lot of potential energy

second law of thermodynamics

when energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes