chapter 24

Question 1

nutrient
major nutrients
other nutrients

Answer 1

Nutrient: a substance in food that promotes normal growth, maintenance, and repair
Major nutrients
Carbohydrates, lipids, and proteins
Other nutrients
Vitamins and minerals (and, technically speaking, water)

Question 2

Carbohydrates

dietary sources

Answer 2

Dietary sources

Starch (complex carbohydrates) 
grains and vegetables
Sugars 
fruits, sugarcane, sugar beets, honey and milk
Insoluble fiber
cellulose in vegetables
provides roughage
Soluble fiber: 
pectin in apples and citrus fruits
reduces blood cholesterol levels

Question 3

Carbohydrates uses
Glucose fuel
Neurons and RBCs
Excess glucose is

Answer 3

Uses
Glucose fuel used by cells to make ATP
Neurons and RBCs rely almost entirely on glucose
Excess glucose is converted to glycogen or fat and stored

Question 4

carbs dietary requirements

Answer 4

Dietary requirements
Minimum 100 g/day to maintain adequate blood glucose levels
Recommended minimum 130 g/day
Recommended intake: 45–65% of total calorie intake; mostly complex carbohydrates

Question 5

lipids dietary sources

essentail fatty acids

Answer 5

Dietary sources
Triglycerides
Saturated fats 
meat, dairy foods, and tropical oils
Unsaturated fats 
seeds, nuts, olive oil, and most vegetable oils
Cholesterol 
egg yolk, meats, organ meats, shellfish, and milk products

Essential fatty acids
Linoleic and linolenic acid,
in most vegetable oils
Must be ingested

Question 6

Lipids essential uses of lipids in the body
Help absorb
Major fuel of 
Phospholipids are essential in
functions of fatty deposits
Concentrated source of e

Answer 6

Essential uses of lipids in the body
Help absorb fat-soluble vitamins
Major fuel of hepatocytes and skeletal muscle
Phospholipids are essential in myelin sheaths and all cell membranes
Functions of fatty deposits (adipose tissue)
Protective cushions around body organs
Insulating layer beneath the skin
Concentrated source of energy

Question 7

Lipids regulatory functions

functions of cholesterol

Answer 7

Regulatory functions
Smooth muscle contraction
Control of blood pressure
Inflammation
Functions of cholesterol
Stabilizes membranes
Precursor of bile salts and steroid hormones

Question 8

Lipids dietary requirements
Fats should represent
Saturated fats
Daily cholesterol intake

Answer 8

Dietary requirements suggested by the American Heart Association
Fats should represent 30% or less of total caloric intake
Saturated fats should be limited to 10% or less of total fat intake
Daily cholesterol intake should be no more than 300 mg

Question 9

Proteins Dietary sources

and dietary requirements and uses

Answer 9

Dietary sources
Eggs, milk, fish, and most meats
Legumes, nuts, and cereals contain incomplete proteins (lack some essential amino acids)
Legumes and cereals together contain all essential amino acids
Dietary requirements
Rule of thumb: daily intake of 0.8 g per kg body weight
Uses
Structural materials
keratin, collagen, elastin, muscle proteins
Most functional molecules
enzymes, some hormones

Question 10

use of amino acids in the body

Answer 10

Use of amino acids in the body
1. All-or-none rule
All amino acids needed must be present for protein synthesis to occur

2.Adequacy of caloric intake
Protein will be used as fuel if there is insufficient carbohydrate or fat available

3. Nitrogen balance
   State where the rate of protein synthesis equals the rate of breakdown and loss
   Positive if synthesis exceeds breakdown (normal in children and tissue repair)
   Negative if breakdown exceeds synthesis (e.g., stress, burns, infection, or injury)

4.Hormonal controls
Anabolic hormones (GH, sex hormones) accelerate protein synthesis

Question 11

Vitamins
Crucial in
Most function as

Answer 11

Organic compounds
Crucial in helping the body use nutrients
Most function as coenzymes
Vitamins D, some B, and K are synthesized in the body

Question 12

Vitamins two types based on ____

Answer 12

Two types, based on solubility
Water-soluble vitamins
B complex and C are absorbed with water
B12 absorption requires intrinsic factor
Not stored in the body 
Fat-soluble vitamins
A, D, E, and K are absorbed with lipid digestion products
Stored in the body, except for vitamin K
Vitamins A, C, and E act as antioxidants

Question 13

Minerals
Work with
Uptake and excretion must be

Answer 13

Seven required in moderate amounts:
Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium
Others required in trace amounts
Work with nutrients to ensure proper body functioning
Uptake and excretion must be balanced to prevent toxic overload

Question 14

minerals examples
harden bone
essential for oxygen binding to hemoglobin
necessary for thyroid hormone synthesis
major electrolytes in the blood

Answer 14

Examples
Calcium, phosphorus, and magnesium salts harden bone
Iron is essential for oxygen binding to hemoglobin
Iodine is necessary for thyroid hormone synthesis
Sodium and chloride are major electrolytes in the blood

Question 15

Metabolism

Answer 15

Metabolism
biochemical reactions inside cells involving nutrients
Two types of reactions
Anabolism
synthesis of large molecules from small ones
Catabolism
hydrolysis of complex structures to simpler ones

Question 16

Cellular respiration
Enzymes shift
Phosphorylated molecules are

Answer 16

Cellular respiration
catabolism of food fuels and capture of energy to form ATP in cells
Enzymes shift high-energy phosphate groups of ATP to other molecules (phosphorylation)
Phosphorylated molecules are activated to perform cellular functions

Question 17

Stages of metabolism

Answer 17

Processing of nutrients
1. Digestion, absorption and transport to tissues

2.Cellular processing (in cytoplasm)
Synthesis of lipids, proteins, and glycogen (anablolism)
Catabolism (glycolysis) into intermediates

3.Oxidative (mitochondrial) breakdown of intermediates into CO2, water, and ATP

Question 18

Oxidation-Reduction (Redox) Reactions
Oxidized substances
Reduced substances
Coenzymes act as

Answer 18

Oxidation
gain of oxygen or loss of hydrogen
Oxidation-reduction (redox) reactions
Oxidized substances lose electrons and energy
Reduced substances gain electrons and energy
Coenzymes act as hydrogen (or electron) acceptors
Nicotinamide adenine dinucleotide (NAD+)
Flavin adenine dinucleotide (FAD)

Question 19

ATP Synthesis two mechanisms

Answer 19

Two mechanisms
Substrate-level phosphorylation
Oxidative phosphorylation

Question 20

Substrate-Level Phosphorylation

occurs in

Answer 20

High-energy phosphate groups directly transferred from phosphorylated substrates to ADP
Occurs in glycolysis and the Krebs cycle
Also occurs in certain muscle fibers

Question 21

Oxidative Phosphorylation
_____ Process
occurs only in the

Answer 21

Chemiosmotic process
Couples the movement of substances across a membrane to chemical reactions
In the mitochondria
Carried out by electron transport proteins
Nutrient energy is used to create H+ gradient across mitochondrial membrane
H+ flows through ATP synthase
Energy is captured and attaches phosphate groups to ADP
We will look more closely at this in a few minutes when we discuss electron transport.

• Electron trasport protein “pump” protons, creating a proton gradient.
• ATP synthase uses the energy of the proton gradient to bind phosphate groups to ADP
• Occurs only in the mitochondrial matrix

Question 22

Carbohydrate Metabolism

Glucose is catabolized in three pathways

Answer 22

Oxidation of glucose
C6H12O6 + 6O2  6H2O + 6CO2 + 36 ATP + heat
Glucose is catabolized in three pathways (3 steps to cellular respiration)
Glycolysis
Krebs cycle
Electron transport chain and oxidative phosphorylation

Question 23

Glycolysis
\_\_ step pathway
occurs in \_\_\_
\_\_->\_\_\_
three major phases

Answer 23

10-step pathway
Anaerobic
Occurs in the cytosol
Glucose → 2 pyruvic acid molecules
Three major phases
Sugar activation
Sugar cleavage
Sugar oxidation and ATP formation

Question 24

phase 1 sugar activation

Answer 24

phosphorylation activates glucose. Glucose is converted to fructose-1,6-biphophate. 2 ATP molecules are used

Question 25

Phase 2 Sugar cleavage:

Answer 25

fructose-1,6-biphophate is split into two 3-carbon fragments

Question 26

Phase 3 sugar oxidation and ATP formation

Answer 26

the 3-carbond fragments are oxidized (by removing hydrogen) and 4 ATP molecules are formed

Question 27

``` final products of glycolysis Converted to lactic acid if Enter aerobic pathways if 2 NADH + H+ (reduced Net gain of ```

Answer 27

Final products of glycolysis 2 pyruvic acid Converted to lactic acid if O2 not readily available Enter aerobic pathways if O2 is readily available 2 NADH + H+ (reduced NAD+) Net gain of 2 ATP

Question 28

Krebs Cycle ``` occurs in the fueled by transitional phase Each pyruvic acid is converted to Decarboxylation: Oxidation, H+ is removed from Acetic acid + coenzyme A = ```

Answer 28

Occurs in mitochondrial matrix Fueled by pyruvic acid and fatty acids Transitional phase Each pyruvic acid is converted to acetyl CoA Decarboxylation: removal of 1 C to produce acetic acid and CO2 Oxidation: H+ is removed from acetic acid and picked up by NAD+ Acetic acid + coenzyme A forms acetyl CoA

Question 29

Coenzyme A shuttles acetic acid to an Each acetic acid is

Answer 29

Coenzyme A shuttles acetic acid to an enzyme of the Krebs cycle Each acetic acid is decarboxylated and oxidized, generating: 3 NADH + H+ 1 FADH2 2 CO2 1 ATP

Question 30

Krebs cycle does not what? Breakdown products of Cycle intermediates may be used as

Answer 30

Does not directly use O2 Breakdown products of fats and proteins can also enter the cycle Cycle intermediates may be used as building materials for anabolic reactions

Question 31

Electron Transport Chain and Oxidative Phosphorylation The part of metabolism that directly Chain of proteins bound to Substrates NADH + H+ and FADH2 deliver

Answer 31

The part of metabolism that directly uses oxygen Chain of proteins bound to metal atoms (cofactors) on inner mitochondrial membrane, cristae) Substrates NADH + H+ and FADH2 deliver hydrogen atoms

Question 32

Electron Transport Chain and Oxidative Phosphorylation Hydrogen atoms are Electrons are shuttled along the Released energy is used to Respiratory enzyme complexes I, III, and IV pump H+ diffuses back to the ATP synthase uses released energy to make Electrons are delivered to O– attracts

Answer 32

Hydrogen atoms are split into H+ and electrons Electrons are shuttled along the inner mitochondrial membrane, losing energy at each step Released energy is used to pump H+ into the intermembrane space Respiratory enzyme complexes I, III, and IV pump H+ into the intermembrane space H+ diffuses back to the matrix via ATP synthase ATP synthase uses released energy to make ATP Electrons are delivered to O, forming O– O– attracts H+ to form H2O

Question 33

Electronic Energy Gradient | This energy is released in a stepwise manner through th

Answer 33

Transfer of energy from NADH + H+ and FADH2 to oxygen releases large amounts of energy This energy is released in a stepwise manner through the electron transport chain

Question 34

Glycogenesis and Glycogenolysis

Answer 34

Glycogenesis Glycogen formation when glucose supplies exceed need for ATP synthesis Mostly in liver and skeletal muscle Glycogenolysis Glycogen beakdown in response to low blood glucose

Question 35

Gluconeogenesis Mainly in the Protects against

Answer 35

Glucose formation from noncarbohydrate (glycerol and amino acid) molecules Mainly in the liver Protects against damaging effects of hypoglycemia

Question 36

``` Lipid Metabolism Fat catabolism yields Most products of fat digestion are Only triglycerides are routinely The two building blocks are oxidized separately ```

Answer 36

Fat catabolism yields 9 kcal per gram (vs 4 kcal per gram of carbohydrate or protein) Most products of fat digestion are hydrolyzed by endothelial enzymes into fatty acids and glycerol Only triglycerides are routinely oxidized for energy The two building blocks are oxidized separately Glycerol pathway Fatty acid pathway

Question 37

Lipogenesis occurs when cellular ___ and ___ are ___ Glucose is easily converted into fat because acetyl CoA is

Answer 37

Triglyceride synthesis occurs when cellular ATP and glucose levels are high Glucose is easily converted into fat because acetyl CoA is An intermediate in glucose catabolism A starting point for fatty acid synthesis

Question 38

Lipolysis Oxaloacetic acid is necessary for Without it, acetyl CoA is converted

Answer 38

The reverse of lipogenesis Oxaloacetic acid is necessary for complete oxidation of fat Without it, acetyl CoA is converted by ketogenesis in the liver into ketone bodies (ketones)

Question 39

``` Synthesis of Structural Materials Phospholipids for Cholesterol for In the liver synthesis of transport of Synthesis of cholesterol from Use of cholesterol to form ```

Answer 39

Phospholipids for cell membranes and myelin Cholesterol for cell membranes and steroid hormone synthesis In the liver Synthesis of transport lipoproteins for cholesterol and fats Synthesis of cholesterol from acetyl CoA Use of cholesterol to form bile salts

Question 40

Protein Metabolism | When dietary protein is in excess, amino acids are

Answer 40

When dietary protein is in excess, amino acids are Oxidized for energy Converted into fat for storage

Question 41

Protein Synthesis is ___ controlled requires a ___ of amino acids essentail amino acids must be provided in ___

Answer 41

Is hormonally controlled Requires a complete set of amino acids Essential amino acids must be provided in the diet

Question 42

Catabolic-Anabolic Steady State

Answer 42

A dynamic state in which Organic molecules (except DNA) are continuously broken down and rebuilt Organs have different fuel preferences

Question 43

Absorptive and Postabsorptive States

Answer 43

``` Absorptive (fed) state During and shortly after eating Absorption of nutrients is occurring Postabsorptive (fasting) state When the GI tract is empty Energy sources are supplied by breakdown of reserves ```

Question 44

Sources of Blood Glucose Postabsorpative Glycogenolysis in the ___ and ___ Lipolysis in ____ and ____ Catabolism of cellular protein during Amino acids are deaminated and used for gluconeogenesis in the ___ and later in the _____

Answer 44

Glycogenolysis in the liver Glycogenolysis in skeletal muscle Lipolysis in adipose tissues and the liver Glycerol is used for gluconeogenesis in the liver Catabolism of cellular protein during prolonged fasting Amino acids are deaminated and used for gluconeogenesis in the liver and (later) in the kidneys

Question 45

Postabsorptive State: Hormonal Controls Glucagon release is stimulated by Glucagon, a hyperglycemic hormone, promotes

Answer 45

Glucagon release is stimulated by Declining blood glucose Rising amino acid levels Glucagon, a hyperglycemic hormone, promotes Glycogenolysis and gluconeogenesis in the liver Lipolysis in adipose tissue Modulation of glucose effects after a high-protein, low-carbohydrate meal

Question 46

Postabsorptive State: Neural Controls

Answer 46

In response to low plasma glucose, or during fight-or-flight or exercise, the sympathetic nervous system and epinephrine from the adrenal medulla promote Fat mobilization Glycogenolysis

Question 47

Metabolic Role of the Liver Process nearly every Play a major role in regulating plasma Store Metabolize

Answer 47

Hepatocytes (liver cells) Process nearly every class of nutrient Play a major role in regulating plasma cholesterol levels Store vitamins and minerals Metabolize alcohol, drugs, hormones, and bilirubin

Question 48

``` Cholesterol Structural basis of Major component of Makes up part of the Transported in ```

Answer 48

Structural basis of bile salts, steroid hormones, and vitamin D Major component of plasma membranes Makes up part of the hedgehog signaling molecule that directs embryonic development Transported in lipoprotein complexes containing triglycerides, phospholipids, cholesterol, and protein

Question 49

Lipoproteins

Answer 49

``` Types of lipoproteins HDLs (high-density lipoproteins) The highest protein content LDLs (low-density lipoproteins) Cholesterol-rich VLDLs (very low density lipoproteins) Mostly triglycerides Chylomicrons ```

Question 50

High levels of HDL are thought to | High levels of LDL, especially lipoprotein (a) increase the risk of

Answer 50

High levels of HDL are thought to protect against heart attack High levels of LDL, especially lipoprotein (a) increase the risk of heart attack

Question 51

Plasma Cholesterol Levels The liver produces cholesterol Saturated fatty acids Unsaturated fatty acids Trans fats

Answer 51

The liver produces cholesterol At a basal level regardless of dietary cholesterol intake In response to saturated fatty acids Saturated fatty acids Stimulate liver synthesis of cholesterol Inhibit cholesterol excretion from the body Unsaturated fatty acids Enhance excretion of cholesterol Trans fats Increase LDLs and reduce HDLs

Question 52

Unsaturated omega-3 fatty acids (found in cold-water fish)

Answer 52

Unsaturated omega-3 fatty acids (found in cold-water fish) Lower the proportions of saturated fats and cholesterol Have antiarrhythmic effects on the heart Help prevent spontaneous clotting Lower blood pressure

Question 53

Non-Dietary Factors Affecting Cholesterol stress smoking cigs aerobic exercise apple pear

Answer 53

Stress, cigarette smoking, and coffee lower HDL levels Aerobic exercise and estrogen increase HDL levels and decrease LDL levels Body shape “Apple”: Fat carried on the upper body is correlated with high cholesterol and LDL levels “Pear”: Fat carried on the hips and thighs is correlated with lower cholesterol and LDL levels

Question 54

Energy Balance

Answer 54

Bond energy released from food must equal the total energy output Energy intake = the energy liberated during food oxidation Energy output Immediately lost as heat (~60%) Used to do work (driven by ATP) Stored as fat or glycogen

Question 55

heat energy

Answer 55

Heat energy Cannot be used to do work Warms the tissues and blood Helps maintain the homeostatic body temperature Allows metabolic reactions to occur efficiently

Question 56

Obesity

Answer 56

Body mass index (BMI) = 
wt (lb) × 705/ht (inches)2 Considered overweight if BMI is 25 to 30 Considered obese if BMI is greater than 30 Higher incidence of atherosclerosis, diabetes mellitus, hypertension, heart disease, and osteoarthritis

Question 57

Long-Term Regulation of Food Intake additional factors

Answer 57

``` Additional factors Temperature Stress Psychological factors Adenovirus infections Sleep deprivation ```

Question 58

Metabolic Rate

Answer 58

Total heat produced by chemical reactions and mechanical work of the body Measured directly with a calorimeter or indirectly with a respirometer Basal metabolic rate (BMR) Reflects the energy the body needs to perform its most essential activities

Question 59

Factors that Influence BMR As the ratio of body surface area to volume increases, BMR _____ with age ______with temperature or stress

Answer 59

As the ratio of body surface area to volume increases, BMR increases Decreases with age Increases with temperature or stress Males have a disproportionately higher BMR Thyroxine increases oxygen consumption, cellular respiration, and BMR

Question 60

total Metabolic Rate

Answer 60

Total metabolic rate (TMR) Rate of kilocalorie consumption to fuel all ongoing activities Increases with skeletal muscle activity and food ingestion

Question 61

Regulation of Body Temperature At rest, During exercise, heat production from

Answer 61

Body temperature reflects the balance between heat production and heat loss At rest, the liver, heart, brain, kidneys, and endocrine organs generate most heat During exercise, heat production from skeletal muscles increases dramatically

Question 62

Regulation of Body Temperature normal body temp optimal enzyme activity occurs increased temp ___

Answer 62

Normal body temperature = 37°C (98.6°F) Optimal enzyme activity occurs at this temperature Increased temperature denatures proteins and depresses neurons

Question 63

Mechanisms of Heat Exchange | four mechanisms

Answer 63

Four mechanisms Radiation is the loss of heat in the form of infrared rays Conduction is the transfer of heat by direct contact Convection is the transfer of heat to the surrounding air Evaporation is the heat loss due to the evaporation of water from body surfaces

Question 64

Core and Shell Temperature _____ is the major agent of heat exchange between the core and the shell Core temperature vs. shell temperature

Answer 64

Organs in the core have the highest temperature Blood is the major agent of heat exchange between the core and the shell Core temperature is regulated Core temperature remains relatively constant, while shell temperature fluctuates substantially (20°C–40°C)

Question 65

Mechanisms of Heat Exchange Insensible heat loss accompanies insensible Evaporative heat loss becomes sensible (active) when body temperature

Answer 65

Insensible heat loss accompanies insensible water loss from lungs, oral mucosa, and skin Evaporative heat loss becomes sensible (active) when body temperature rises and sweating increases water vaporization

Question 66

Hyperthermia depresses the (heat stroke) begins at core temperature of ___

Answer 66

Hyperthermia Elevated body temperature depresses the hypothalamus Positive-feedback mechanism (heat stroke) begins at core temperature of 41°C Can be fatal if not corrected

Question 67

hyporthermia | Shivering stops at core temperature of

Answer 67

Hypothermia Low body temperature where vital signs decrease Shivering stops at core temperature of 30 - 32°C Can progress to coma a death by cardiac arrest at ~ 21°C

Question 68

Heat exhaustion

Answer 68

Heat exhaustion Heat-associated collapse after vigorous exercise Due to dehydration and low blood pressure Heat-loss mechanisms are still functional May progress to heat stroke

Question 69

hypothermia

Answer 69

Hypothermia Low body temperature where vital signs decrease Shivering stops at core temperature of 30 - 32°C Can progress to coma a death by cardiac arrest at ~ 21°C

Question 70

fever

Answer 70

Controlled hyperthermia | Due to infection (also cancer, allergies, or CNS injuries)