Exam 3: Chapter 25: Nutrition, Metabolism, and Temperature Regulation

Question 1

The total of all the chemical reactions that occur in the body

Answer 1

Metabolism

Question 2

*Includes the energy-releasing process by which large molecules are broken down into smaller molecules
*______ of nutrients begins during digestion when large molecules, such as polysaccharides and fats, are broken down for absorption by the small intestine
*The process of _____ continues in the cells when the absorbed nutrients are further broken down for ATP production
*The energy derived from ______ is used to drive anabolic reactions and processes such as active transport and muscle contraction

Answer 2

Catabolism

Question 3

*Includes the energy-requiring process by which small molecules are joined to form larger molecules
*Occurs in all the body cells as they divide to form new cells, maintain their own intracellular structure, and produce molecules, such as hormones, neurotransmitters, and extracellular matrix molecules, for export

Answer 3

Anabolism

Question 4

Step 1. Glycolysis
Step 2. Acetyl Co-A formation
Step 3. Citric Acid Cycle
Step 4. Oxidative phosphorylation

Answer 4

There are Four Steps of Cellular Respiration

Question 5

*Carbohydrate metabolism begins with _____, a series of chemical reactions in the cytosol that results in the breakdown of glucose into two pyruvate molecules
*Each glucose molecule that enters ______ forms two glyceraldehyde-3-phosphate molecules at the sugar cleavage phase
*Each glyceraldehyde-3-phosphate molecule produces two ATP molecules, one NADH molecule, and one pyruvate molecule
*The breakdown of each glucose molecule, therefore, produces four ATP, two NADH, and two pyruvate molecules
*Because the start of ______ requires the input of two ATP molecules, the final yield of each glucose molecule is two ATP, two NADH, and two pyruvate molecules
*If the cell has adequate amounts of O2, the NADH and pyruvate molecules are used in aerobic respiration to produce ATP
*In the absence of sufficient O2, they are used in anaerobic respiration.
*_____ in the cytosol converts glucose to two pyruvate molecules and produces two ATP and two NADH
*The two NADH can move to the inner mitochondrial membrane to participate in the electron transport chain
*Occurs in the cytoplasm

Answer 5

Glycolysis

Question 6

Input of ATP
Sugar Cleavage
NADH Production
ATP and Pyruvate Production

Answer 6

Glycolysis is Divided into Four Phases

Question 7

*The first steps in glycolysis require the input of energy in the form of two ATP molecules
The energy is necessary to make the glucose molecule, a relatively stable molecule, more reactive
An ATP molecule is used in the process called phosphorylation, where a phosphate group is transferred from ATP to glucose
This first step forms glucose-6-phosphage
The glucose-6-phosphate atoms are rearranged to from fructose-6-phosphate
A second ATP molecule is then used to phosphorylate fructose-6-phosphate, producing fructose-1, 6-bisphosphate

Answer 7

Input of ATP

Question 8

*Fructose-1, 6-biphosphate is cleaved, or broken, into two 3-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
Dihydroxyacetone phosphate is rearranged to form a second glyceraldehyde-3-phosphate; consequently, two molecules of glyceraldehyde-3-phosphate result

Answer 8

Sugar Cleavage

Question 9

*Each glyceraldehyde-3-phosphate molecule is oxidized (loses two electrons) to form 1,3. Bisphosphoglyceric acid
In addition, nicotinamide adenine dinucleotide (NAD+) is reduced (gains two electrons) to NADH
Glyceraldehyde-3-phosphate also loses two H+, one of which binds to NAD+:
NAD+ +2e- +2H+ —> NADH + H+
NADH is referred to as an electron-carrier molecule
The two high-energy electrons (e-) gained by NADH can be used to produce ATP molecules through the electron transport chain

Answer 9

NADH Production

Question 10

*The last phase of glycolysis produces two ATP molecules and one pyruvate molecule from each 1,3-bisphosphoglyceric acid molecule
Because the previous phase produced two 1,3-bisphosphoglyceric acid molecules, this phase produces four ATP molecules and two pyruvate molecules

Answer 10

ATP and Pyruvate Production

Question 11

*The two pyruvate molecules in glycolysis are converted to two acetyl-CoA molecules, producing CO2 and NADH
oThe NADH can move to the inner mitochondrial membrane to participate in the electron-transport chain
*The pyruvate moves from the cytosol into a mitochondrion
oA mitochondrion is separated into the intermembrane space and the matrix by the inner mitochondrial membrane
*Within the matrix, enzymes remove a carbon and two oxygen atoms from the 3-carbon pyruvate molecule to from CO2 and a 2-carbon acetyl group
oDuring this reaction, H+ and electrons are also released and used to reduce NAD+ to NADH
oThe acetyl group combines with coenzyme A (CoA) to form acetyl-CoA
oFor each two pyruvate molecules from glycolysis, two acetyl-CoA molecules, two CO2 molecules, and two NADH are formed during this phase
*Pyruvate converted to acetyl Co-A

Answer 11

Acetyl Co-A Formation

Question 12

*Within the mitochondrial matrix, the two acetyl-CoA molecules enter the citric acid cycle, which produces four CO2, six NADH, two FADH2, and two ATP
oThe NADH and FADH2 can move to the inner mitochondrial membrane to participate in the electron transport chain
*The third phase of aerobic respiration is the citric acid cycle, which is named after the 6-carbon citric acid molecule formed in the first step of the cycle
oThe citric acid cycle begins with the production of citric acid
oThis occurs when the 2-carbon acetyl- CoA, produced in the second phase, combines with a 4-carbon molecule called oxaloacetic acid
oA series of reactions occurs in which the citric acid molecule is modified, producing ATP, electron carriers (NADH and FADH2), and CO2
oAs the cycle proceeds, another oxaloacetic acid molecule is produced
oThis new oxaloacetic acid can start the cycle again by combining with another acetyl-CoA
*The citric acid cycle involves the reduction of citric acid molecules, formed from acetyl-CoA and oxaloacetic acid
*Occurs in the matrix of the mitochondria
*Completes the glucose oxidation by breaking down the acetyl CoA into carbon dioxide

Answer 12

Citric Acid Cycle

Question 13

ATP production
NADH and FADH2 production
Carbon dioxide production

Answer 13

During the Reactions of the Citric Acid Cycle, Three Important Events Occur

Question 14

For each citric acid molecule, one ATP is formed

Answer 14

ATP Production

Question 15

*For each citric acid molecule, three NAD+ molecules are converted to NADH molecules, and one flavin adenine dinucleotide (FAD) molecule is converted to FADH2
The NADH and FADH2 molecules are electron carriers that enter the electron-transport chain and are used to produce ATP

Answer 15

NADH and FADH2 Production

Question 16

*Each 6-carbon citric acid molecule at the start of the cycle becomes a 4-carbon oxaloacetic acid molecule at the end of the cycle
Two carbon and four oxygen atoms from the citric acid molecule are used to form two CO2 molecules
Thus, some of the carbon and oxygen atoms that make up food molecules, such as glucose, are eventually eliminated from the body as CO2
Humans literally breathe out part of the food they eat

Answer 16

Carbon Dioxide Production

Question 17

*At the inner mitochondrial membrane, the electron-transport chain uses NADH and FADH2 to produce 28 ATP
oThis process requires O2, which combines with H+ to form H2O
*Oxygen is the final acceptor of electrons in this process
*Without O2 to accept the electrons, the reactions of the electron-transport chain cease, effectively stopping aerobic respiration
*The H+ released from NADH and FADH2 is moved from the intermembrane space to the matrix by active transport
*As a result, the concentration of H+ in the intermembrane space exceeds that of the matrix and a H+ concentration gradient is established
*The H+ cannot simply diffuse down the concentration gradient but must pass through certain channels formed by an enzyme called ATP synthase
*As the H+ diffuses down the concentration gradient, energy is release that is used to produce ATP
*This process is called chemiosmosis because the chemical formation of ATP is coupled to a diffusion force similar to osmosis
*Occurs along the inner membrane of the mitochondria
*Involves an electron transport chain

Answer 17

Oxidative Phosphorylation (Electron Transport Chain)

Question 18

oAt the beginning of this phase, electrons are transferred from NADH and FADH2 to the electron-transport carriers
Electrons and H+ are released from NADH and FADH2
After the loss of the electrons and the H+, the oxidized NAD+ and FAD are reused to transport additional electrons from the citric acid cycle to the electron-transport chain
oThe electrons released from NADH and FADH2 pass from one electron carrier to the next through a series of oxidation-reduction reactions
Three of the electron carriers also function as proton pumps, which move the H+ from the mitochondrial matrix into the intermembrane space
Each proton pump accepts an electron, uses some of the electron’s energy to export a H+, and passes the electron to the next electron carrier
oThe last electron carrier in the series collects the electrons and combines them with O2 and H+ to form water:
1/2 O2 + 2H+ + 2e- —> H2O

Answer 18

Activity of the Electron Transport Chain

Question 19

Substrate-level phosphorylation
Oxidative phosphorylation

Answer 19

During Cellular Respiration, ATP is Produced by

Question 20

*Is the breakdown of glucose in the absence of O2
*In human cells, the breakdown of a glucose molecule in the absence of O2 produces two molecules of lactate and two molecules of ATP
*The ATP thus produced is a source of energy during activities such as intense exercise, when insufficient O2 is delivered to tissues
*When O2 becomes available, the lactate in the liver can be converted through a series of chemical reactions into glucose
*The glucose then can be released from the liver and transported in the blood to cells that use glucose for energy
*This process of converting lactate to glucose is called the Cori cycle
*Some of the reactions involved in this process require energy derived from ATP that is produced by aerobic respiration
*The O2 is necessary for synthesizing the ATP is part of the oxygen deficit

Answer 20

Anaerobic Respiration

Question 21

Glycolysis
Lactate Formation

Answer 21

Anaerobic Glycolysis can be divided into two phases

Question 22

*Glucose undergoes several reactions to produce two pyruvate and two NADH
There is also a net gain of two ATP molecules

Answer 22

Glycolysis

Question 23

*Pyruvate is first converted to lactic acid, a reaction that requires the input of energy from the NADH produced in step 3 of glycolysis
In cells, lactic acid usually releases a H+ and is converted to lactate, the ionized form of lactic acid
Lactate is released from the cells that produce it, and blood transports it to the liver

Answer 23

Lactate Formation

Question 24

*Are the main lipid stored in adipose tissue
*Synthesis and breakdown of ______ occur constantly; thus, the lipids present in adipose tissue today are not the same lipids that were there a few weeks ago
*Glycerol head
*Fatty acid tails
*Beta oxidation

Answer 24

Triglycerides

Question 25

oBetween meals, when triglycerides are broken down in adipose tissue, some of the fatty acids produced are released into the blood, where they are called free _________ oOther tissues, especially skeletal muscle and the liver, use the free _____ as a source of energy

Answer 25

Fatty Acid Tails

Question 26

oThe metabolism of fatty acids occurs by _______, a series of reactions in which two carbon atoms are removed from the end of a fatty acid chain to form acetyl-CoA oThe process of _____ continues to remove two carbon atoms at a time until the entire fatty acid chain is converted into acetyl-CoA molecules oAcetyl-CoA can enter the citric acid cycle and be used to generate ATP

Answer 26

Beta Oxidation

Question 27

*Acetyl-CoA is also used in _______, the formation of ketone bodies *In the liver, when large amounts of acetyl-CoA are produced, not all of the acetyl-CoA enters the citric acid cycle *Instead, two acetyl-CoA molecules combine to form a molecule of acetoacetic acid, which is converted mainly into β-hydroxybutyric acid, and acetone are called ketone bodies; they are released into the blood, where they travel to other tissues, especially skeletal muscle *In the cells of these tissues, the ketone bodies are converted back into acetyl-CoA, which enters the citric acid cycle to produce ATP *The presence of small amounts of ketone bodies in the blood is normal and beneficial, but excessive production of ketone bodies is called ketosis *Because ketone bodies are acidic, if the increased number of ketone bodies exceeds the capacity of the body’s buffering systems, acidosis, a decrease in blood pH, can occur *Because ketone bodies are derived from the breakdown of fatty acids, conditions that increase lipid metabolism can speed the rate of ketone body formation, thus increasing the possibility of ketosis *Examples of conditions that increase lipid metabolism are starvation, diets consisting mainly of proteins and lipids with few carbohydrates, and untreated diabetes mellitus *Ketone bodies are excreted by the kidneys and diffuse into the alveoli of the lungs *Because ketone bodies are excreted by the kidneys and lungs, the characteristics of untreated diabetes mellitus include ketone bodies in the urine and “acetone breath”

Answer 27

Ketogenesis

Question 28

*Usually, this conversion is accomplished by transferring an amine group from an amino acid to the keto acid, a reaction called _______ *For example, α-ketoglutaric acid (a keto acid) reacts with an amino acid to form glutamic acid (an amino acid) *Most amino acids can undergo ________ to produce glutamic acid

Answer 28

Transamination

Question 29

*The synthesis of________ usually begins with keto acids *A keto acid can be converted into an amino acid by replacing its oxygen atom with an amine group *The glutamic acid provides an amine group that is used to synthesize most of the_______ *A few ______ are formed from the essential amino acids by other chemical reactions

Answer 29

Essential vs Nonessential Amino Acids

Question 30

Oxidative deamination Conversion to intermediates of carbohydrate metabolism

Answer 30

Amino Acids as Energy Source

Question 31

*In ______, or deaminization, an amine group is removed from an amino acid (usually glutamic acid), leaving ammonia and a keto acid *In the process, NAD+ is reduced to NADH, which can enter the electron-transport chain to produce ATP *Although ammonia is toxic to cells, it does not accumulate to toxic levels because the liver converts it to urea, which the blood carries to the kidneys for elimination

Answer 31

Oxidative Deamination

Question 32

*Amino acids can also be converted into the intermediate molecules of carbohydrate metabolism * These molecules are then metabolized to yield ATP *The conversion of an amino acid often begins with a transamination or oxidative deamination reaction, in which the amino acid is converted into a keto acid *The keto acid enters the citric acid cycle or is converted into pyruvate or acetyl-CoA

Answer 32

Conversion to Intermediates of Carbohydrate Metabolism

Question 33

*As blood glucose levels increase, insulin stimulates the movement of glucose from the blood into the cells *Glucose enters most cells by facilitated diffusion and is immediately converted to glucose-6-phosphate, which cannot recross the plasma membrane *Glucose-6-phosphate then continues through glycolysis to produce ATP *However, if excess glucose is present (e.g., after a meal), it is used to form glycogen through a process called ______ *Most of the body’s glycogen is contained in skeletal muscle and the liver *_______, therefore, allows cells to store glucose in the form of glycogen, thereby regulating blood glucose levels

Answer 33

Glycogenesis

Question 34

*Once glycogen stores, which are quite limited, are filled excess glucose, as well as amino acids, are used to synthesize lipids through a process called ________ *Triglycerides are the common lipid produced by _______ *A triglyceride is composed of glycerol and fatty acid chains; therefore, _______ requires the production of these components *Glucose molecules can be used to form glyceraldehyde-3-phosphate, which can then be converted to glycerol *Glucose and amino acids can be used to form acetyl-CoA molecules *These 2-carbon acetyl-CoA molecules can then join together to form fatty acid chains *Glycerol and three fatty acid chains then combine to form triglycerides

Answer 34

Lipogenesis

Question 35

*When blood glucose levels decrease, cells can “tap into their stores” by the breakdown of glycogen into glucose-6-phosphate through a set of reactions called _________ *In skeletal muscle, glucose-6-phosphate continues through glycolysis to produce ATP *The liver can use glucose-6-phosphate for energy or can convert it to glucose, which diffuses into the blood *Although the liver can release glucose into the blood, skeletal muscle cannot because it lacks the necessary enzymes to convert glucose-6-phosphate into glucose

Answer 35

Glycogenolysis

Question 36

*The release of glucose from the liver is necessary to maintain blood glucose levels between meals *Maintaining these levels is especially important to the brain, which normally uses only glucose for an energy source and consumes about two-thirds of the total glucose used each day *When liver glycogen levels are inadequate to supply glucose, the liver can synthesize glucose from molecules other than carbohydrates, such as amino acids and glycerol *The process of synthesizing glucose from noncarbohydrate sources is called _______ *Most amino acids can be converted into citric acid cycle molecules, acetyl-CoA, or pyruvate *Through a series of chemical reactions, these molecules are converted into glucose *Glycerol can be converted to glyceraldehyde-3-phosphate, which in turn can be converted to glucose

Answer 36

Gluconeogenesis

Question 37

*Is the period immediately after a meal, when nutrients are being absorbed through the intestinal wall into the circulatory and lymphatic systems *Usually lasts about 4 hours after each meal, through the rate of absorption declines after 1-2 hours *During this time the cells use most of the glucose that enters the blood for the energy they require *The remainder of the glucose is converted into glycogen or lipids *Most of the absorbed lipids are deposited in adipose tissue *Many of the absorbed amino acids are used by cells in protein synthesis, some are used for energy, and still others enter the liver and are converted into lipids or carbohydrates

Answer 37

Absorptive State