BIO 100 Chptr 4

Question 1

aer-

Answer 1

air: aerobic respiration—a respiratory process that requires oxygen.

Question 2

an-

Answer 2

without: anaerobic respiration—a respiratory process that does not require oxygen.

Question 3

ana-

Answer 3

up: anabolism—cellular processes in which smaller molecules are built up into larger ones.

Question 4

cata-

Answer 4

down: catabolism—cellular processes that break down larger molecules into smaller ones.

Question 5

co-

Answer 5

with: coenzyme—substance that unites with a protein to complete the structure of an active enzyme molecule.

Question 6

de-

Answer 6

undoing: deamination—a process that removes nitrogen-containing portions of amino acid molecules.

Question 7

mut-

Answer 7

change: mutation—change in genetic information.

Question 8

-strat

Answer 8

spread out: substrate—substance upon which an enzyme acts.

Question 9

sub-

Answer 9

under: substrate—substance upon which an enzyme acts.

Question 10

-zym

Answer 10

causing to ferment: enzyme—protein that speeds up a chemical reaction without itself being consumed.

Question 11

metabolism

Answer 11

At the biochemical level, metabolism (mĕ-tab′ o-lizm) refers to the building up and breaking down of molecules.

Question 12

anabolism

Answer 12

In anabolism (ăh-nab′o-liz″-ĕm), small molecules are built up into larger ones, requiring energy.

Question 13

catabolism

Answer 13

In catabolism (kă-tab′o-liz″-ĕm), larger molecules are broken down into smaller ones, releasing energy.

Question 14

dehydration synthesis

Answer 14

One type of anabolic process, dehydration synthesis (de″hi-dra′shun sin′the-sis), joins certain types of small molecules by removing water molecules.

Question 15

hydrolysis

Answer 15

One type of catabolic reaction is hydrolysis (hi-drol′ĭ-sis), which can decompose carbohydrates, triglycerides, and proteins. A water molecule is consumed for each bond that is broken. Hydrolysis is the reverse of dehydration synthesis.

Question 16

substrate

Answer 16

Enzymes are required in small amounts, because as they work, they are not consumed and can, therefore, function repeatedly. Because of this, a few enzyme molecules can have a powerful effect. Each enzyme type is specific, acting only on a particular type of molecule, called its substrate (sub′strāt). For example, the substrate of an enzyme called catalase (found in the peroxisomes of liver and kidney cells) is hydrogen peroxide, a toxic by-product of certain metabolic reactions. This enzyme’s only function is to decompose hydrogen peroxide into water and oxygen. Without catalase, hydrogen peroxide would accumulate and damage cells. The effects of catalase are easily seen in the foaming of a wound cleaned with hydrogen peroxide.

Question 17

active site

Answer 17

During an enzyme-catalyzed reaction, part of the enzyme molecule called the active site temporarily combines with parts of the substrate molecule, forming an enzyme–substrate complex. (Most enzymes have only one active site.) This interaction strains chemical bonds in the substrate in a way that makes a particular chemical reaction require less energy to proceed. When the reaction happens, the enzyme is released in its original comformation, able to bind another substrate molecule

Question 18

Metabolic pathways

Answer 18

Cellular metabolism includes hundreds of different chemical reactions, each controlled by a specific type of enzyme. Enzymecatalyzed reactions form pathways when the product of one reaction is the substrate of another reaction. Metabolic pathways lead to the synthesis or breakdown of particular biochemicals. Every cell has hundreds of types of enzymes.

Question 19

cofactor

and

coenzymes

Answer 19

Some enzymes become active only when they combine with a nonprotein component called a cofactor. The cofactor helps the active site fold into its appropriate conformation or helps bind the enzyme to its substrate. A cofactor may be an ion of an element, such as copper, iron, or zinc, or a small organic molecule, called a coenzyme (ko-en′zīm). Many coenzymes are composed of vitamin molecules or incorporate altered forms of vitamin molecules.

Question 20

Energy

Answer 20

Energy is the capacity to change something; it is the ability to do work.

Question 21

Cellular respiration

Answer 21

Cellular respiration is the process that transfers energy from molecules such as glucose and makes it available for cellular use.

Question 22

Adenosine triphosphate (ATP)

Answer 22

Adenosine triphosphate (ATP) is a molecule that carries energy in a form that the cell can use. It is the primary energy-carrying molecule in a cell.

Question 23

phosphorylation

Answer 23

ADP can be converted back into ATP using energy released from cellular respiration to attach a third phosphate, in a process called phosphorylation

Question 24

oxidation

Answer 24

Inside cells, fructose ultimately reacts to form glucose. A process called oxidation (ok″sĭ-da′shun) (loss of electrons) releases the energy from the glucose, which is harnessed to power cellular metabolism.

Question 25

cellular respiration

Answer 25

Cellular respiration occurs in three distinct, yet interconnected, series of reactions: glycolysis (gli-kol′ĭ-sis), the citric acid cycle, and the electron transport chain
Cellular respiration requires glucose and oxygen. The products of these reactions include carbon dioxide (CO2), water, and energy. Although most of the energy is lost as heat, almost half is captured as ATP. Figure 4.10 shows how the three components of cellular respiration connect.

Cellular respiration includes aerobic (a″er-ōb′ik) reactions, which require oxygen, and anaerobic (an-a″er-ōb′ik) reactions, which do not. For each glucose molecule decomposed completely by cellular respiration, an estimated theoretical maximum of thirty to thirty-two molecules of ATP can be produced. All but two of the ATP molecules form in the aerobic reactions.

Question 26

Glycolysis

Answer 26

Both aerobic and anaerobic pathways begin with glycolysis. “Glycolysis” means “the breaking of glucose.”
Glycolysis takes place in the cytosol. Because it does not require oxygen, glycolysis is termed the anaerobic phase of cellular respiration.

Glycolysis involves three sets of reactions-
Two phosphate groups are added to a glucose molecule, one at each end, in a step called phosphorylation. This step requires energy from two ATPs, which are used to “prime” the glucose so that it is activated for some of the energy-releasing reactions that will happen.

The 6-carbon glucose molecule is cleaved into two 3-carbon molecules.

The electron carrier NADH is produced, ATP is synthesized, and two 3-carbon pyruvic acid molecules result.

Question 27

NAD+

Answer 27

Some of the reactions of glycolysis release hydrogen atoms. The electrons of these hydrogen atoms contain much of the energy from the chemical bonds of the original glucose molecule. To keep this energy from glucose in a form the cell can use, these hydrogen atoms are passed in pairs to molecules of the hydrogen carrier NAD+ (nicotinamide adenine dinucleotide). In this reaction, two of the electrons and one hydrogen nucleus bind to NAD+ to form NADH.

Question 28

Anaerobic Reactions

Answer 28

Under anaerobic conditions the electron transport chain has no oxygen, and therefore nowhere to unload its electrons. As a result, the electron transport chain can no longer accept new electrons from NADH. As an alternative, NADH + H+ can give its electrons and hydrogens back to pyruvic acid in a reaction that forms lactic acid. Although this reaction regenerates NAD+, the buildup of lactic acid eventually inhibits glycolysis, and ATP production declines. The lactic acid diffuses into the blood, and when oxygen levels return to normal the liver converts the lactic acid back into pyruvic acid, which can finally enter the aerobic pathway.

Question 29

Aerobic Reactions

Answer 29

Pyruvic acid generated by glycolysis can continue through the aerobic pathways if enough oxygen is available. These reactions include the synthesis of acetyl coenzyme A (as′ĕ-til ko-en′zīm A) or acetyl CoA, the citric acid cycle, and the electron transport chain. In addition to carbon dioxide and water, the aerobic reactions yield up to twenty-eight ATP molecules per glucose.

Question 30

Citric Acid Cycle / KREBS

Answer 30

The citric acid cycle begins when a 2-carbon acetyl CoA molecule combines with a 4-carbon oxaloacetic acid molecule to form the 6-carbon citric acid and CoA. The citric acid is changed through a series of reactions back into oxaloacetic acid. The CoA can be used again to combine with acetic acid to form acetyl CoA. The cycle repeats as long as the mitochondrion receives oxygen and pyruvic acid.

Question 31

Electron Transport Chain

Answer 31

The hydrogen and high-energy electron carriers (NADH and FADH2) generated by glycolysis and the citric acid cycle now hold most of the energy contained in the original glucose molecule. To couple this energy to ATP synthesis, the high-energy electrons are handed off to the electron transport chain, which is a series of enzyme-containing complexes that pass electrons. Complexes of the electron transport chain dot the folds of the inner mitochondrial membranes. If these complexes were stretched out, they would be forty-five times as long as the cell membrane in some cells. An electron passed along the electron transport chain gradually loses energy. That energy is transferred to ATP synthase, an enzyme complex that uses the energy to add a phosphate to ADP to form ATP. These reactions are known as oxidation/ reduction reactions.

Question 32

gene

Answer 32

A DNA sequence that contains the information for making a particular polypeptide is called a gene

Question 33

genetic code

Answer 33

The correspondence between a unit of DNA information (3 nucleotides in a row) and a particular amino acid constitutes the genetic code

Question 34

deoxyribonucleic acid (DNA)

Answer 34

The information that instructs a cell to synthesize a particular protein is held in the sequence of nucleotide building blocks of deoxyribonucleic acid (DNA)

Question 35

genome

Answer 35

The complete set of genetic instructions in a cell, including the genes as well as other DNA sequences, constitutes the genome (jēnōm′). A human genome consists of approximately 3.2 billion DNA nucleotides. Only a small part of the human genome encodes protein and it is called the exome (x-ōm). Much of the rest of the genome controls which proteins are produced in a particular cell under particular circumstances and the amounts produced, which is called gene expression.

Question 36

DNS Base pairs

Answer 36

A DNA molecule has a highly regular structure because the bases pair in only two combinations. A DNA base is one of four types: adenine (A), thymine (T), cytosine (C), or guanine (G). A and G are purines (pu′rēnz), and they consist of two organic ring structures. T and C are pyrimidines (pe-rimi-dēnz), and they have a single organic ring structure. A binds to T, and G binds to C. That is, a purine always binds to a pyrimidine, establishing the constant width of the DNA molecule. These pairs—A with T, and G with C—are called complementary base pairs. The sequence of one DNA strand can always be derived from the other by following the “base-pairing rules.” If the sequence of one strand of the DNA molecule is G, A, C, T, then the complementary strand’s sequence is C, T, G, A. The nucleotide sequence provides the information in a molecule of DNA.

Question 37

DNA replication

Answer 37

DNA replication (re″pli-ka′shun) is the process that creates an exact copy of a DNA molecule. It happens during interphase of the cell cycle.

Question 38

RNA (ribonucleic acid)

Answer 38

RNA (ribonucleic acid) molecules accomplish the transfer of information. The process of copying DNA information into an RNA sequence is called transcription
The first step in transcription is the synthesis of messenger RNA (mRNA)

Question 39

messenger RNA (mRNA)

Answer 39

RNA molecules differ from DNA molecules in several ways. RNA nucleotides have ribose rather than deoxyribose sugar. Like DNA, RNA nucleotides each have one of four nitrogenous bases, but whereas adenine, cytosine, and guanine nucleotides are part of both DNA and RNA, thymine nucleotides are only in DNA. In place of thymine nucleotides, RNA molecules have uracil (U) nucleotides. In RNA U pairs with A.

Question 40

codons

Answer 40

Each amino acid in a protein is specified by a series of three bases in DNA and then by a series of three bases in mRNA, called codons

Question 41

translation

Answer 41

To carry out protein synthesis, mRNA must leave the nucleus and associate with a ribosome. There, the mRNA is translated from the “language” of nucleic acids to the “language” of amino acids in a process fittingly called translation

Question 42

Protein Synthesis

Answer 42

Synthesizing a protein molecule requires that the specified amino acid building blocks in the cytoplasm align in the proper sequence along an mRNA, and then attach. A second type of RNA molecule, called transfer RNA (tRNA), aligns amino acids in a way that enables enzymes to bond them to each other

Question 43

anticodon

Answer 43

The other end of each tRNA molecule includes a specific three-nucleotide sequence, called the anticodon, unique to that type of tRNA. An anticodon bonds only to the complementary mRNA codon

Question 44

ribosomal RNA (rRNA)

Answer 44

A ribosome is an organelle that is a tiny particle of two unequal-sized subunits composed of ribosomal RNA (rRNA) molecules and protein molecules.

Question 45

Transcription (In the Nucleus)

Answer 45

RNA polymerase binds to the DNA base sequence of a gene.

This enzyme unwinds and exposes part of the DNA molecule.

RNA polymerase moves along one strand of the exposed gene and catalyzes synthesis of an mRNA, whose nucleotides are complementary to those of the strand of the gene.

When RNA polymerase reaches the end of the gene, the newly formed mRNA is released.

The DNA rewinds and closes the double helix.

The mRNA passes through a pore in the nuclear envelope and enters the cytoplasm.

Question 46

Translation (In the Cytoplasm)

Answer 46

A ribosome binds to the mRNA near the codon at the beginning of the messenger strand.

A tRNA molecule that has the complementary anticodon brings its amino acid to the ribosome.

A second tRNA brings the next amino acid to the ribosome.

A peptide bond forms between the two amino acids, and the first tRNA is released.

This process repeats for each codon in the mRNA sequence as the ribosome moves along its length, forming a chain of amino acids.

The growing amino acid chain folds into the unique conformation of a functional protein.

The completed protein molecule is released. The mRNA, ribosome, and tRNA are recycled.

Question 47

mutagens

Answer 47

Induced mutations are a response to exposure to certain chemicals or radiation, called mutagens (mu′tah-jenz). A familiar mutagen is ultraviolet radiation, which is part of sunlight

Question 48

DNA repair

Answer 48

Cells can detect mutations and correct them. Special “repair enzymes” recognize and remove mismatched nucleotides and fill the resulting gap with the accurate, complementary nucleotides. This mechanism, called the DNA damage response or DNA repair, restores the original DNA sequence.