Download Chapter 3: Diet: Cells & Metabolism

CHAPTER 3
Diet
Cells and Metabolism
Copyright © 2010 Pearson Education, Inc.
Diet
 Current societal pressures to
be thin
 Americans and now fatter
than any time in history
 Health care crisis
 Need to understand
nutrition and metabolism
 What does the body need?
 What size should we be?
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3.1 Nutrients - Macronutrients
Chapter 3
Section 1 Part 1
Nutrients - Macronutrients
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3.1 Nutrients - Macronutrients
 Nutrients: substances in foods that
provide structural materials or energy
 Macronutrients: nutrients that are required
in large amounts
 Water
 Carbohydrates
 Proteins
 Fats
 Micronutrients: required in small amounts
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3.1 Nutrients - Macronutrients
Water
 Adults need about 3 liters per day
 Too little leads to dehydration
 Required for:
 Circulatory system
 Disperse nutrients, oxygen and waste
 Metabolism
 Lost in:
 Waste products
 Cooling by evaporation
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3.1 Nutrients - Macronutrients
Carbohydrates
 main energy source
 Monosaccharides = Simple sugars
(glucose) enter our system quickly
 Polysaccharides = Complex carbohydrates
(branching chains of simple sugars) are
digested more slowly
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3.1 Nutrients - Macronutrients
Sources of Polysaccharide Carbohydrates
 Starch: complex carbohydrate from plants
 Glycogen: complex carbohydrate from
animals
Fructose
monomer
Glucose
monomer
(a) Corn syrup
containing
fructose
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(b) Potatoes containing
starch
Glucose
monomer
(c) Animal muscle
contains glycogen
Figure 3.1
3.1 Nutrients - Macronutrients
Energy is stored within chemical bonds
 Carbon, oxygen and hydrogen bonds
 Breaking the bonds releases energy that the
body can use
 Complex molecules store more energy than
simple molecules
Fructose
monomer
Glucose
monomer
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(a) Corn syrup
(b) Potatoes
containing
containing
starch
Glucose
monomer
(c) Animal muscle
containsFigure
glycogen
3.1
3.1 Nutrients - Macronutrients
Other types of Carbohydrates
 Fiber: indigestible complex carbohydrates
 Essential for large intestine function
 Lowers cholesterol and reduces cancer risk
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3.1 Nutrients - Macronutrients
Proteins
 Polymers of amino acids
 Essential amino acids: we cannot make
these ourselves; must obtain from food
 Complete proteins: contain all the essential
amino acids we need
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3.1 Nutrients - Macronutrients
 Plant proteins can be combined to make
them complete.
(a) Lentils are high in lysine and low in valine.
(b) Rice is low in lysine and high in valine.
The side groups of
lysine and valine
are different.
Lysine
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Valine
Lysine
Valine
Figure 3.2
3.1 Nutrients - Macronutrients
Fats
 Energy storage molecules
 Consist of a glycerol attached to fatty acid
tails
 Essential fatty acids: we cannot make
these ourselves (e.g., omega-3 and omega6)
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3.1 Nutrients - Macronutrients
Fats
 Saturated fats: fatty acid carbons are bound
to as much hydrogen as possible
 Solid at room temperature
 Most animal fats are saturated
(a) Saturated fat
Glycerol
Hydrocarbons (fatty acid tails)
All carbon atoms
make four bonds:
Butter
When carbon atoms
are single-bonded to
each other, each
carbon can bond to
two hydrogens.
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Fats with mostly saturated
hydrocarbons pack tightly
together and are solid at
room temperature.
Figure 3.4a
3.1 Nutrients - Macronutrients
Fats
 Unsaturated fats are not bound to as much
hydrogen as possible
 Monounsaturated and polyunsaturated fats
 Liquid at room temperature
 Most plant fats (oils) are unsaturated or
polyunsaturated
(b) Unsaturated fat
Glycerol
Hydrocarbons (fatty acid tails)
Oil
When carbon atoms
are double-bonded
to each other, each
carbon can bond to
only one hydrogen.
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Fats with many unsaturated
hydrocarbons are kinked
and do not pack tightly.
They are liquid at room
temperature.
Figure 3.4b
3.1 Nutrients - Macronutrients
Fats
 Trans fats: artificially produced fats
 Hydrogenated vegetable oils under
pressure to make solid fat (e.g.,
shortening and margarine)
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3.1 Nutrients - Macronutrients
 Fats
 Trans fats: artificially
produced fats
 May be linked to an
increased risk of heart
disease and diabetes
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3.1 Nutrients - Macronutrients
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3.1 Nutrients - Macronutrients
Chapter 3
End of Section 1 Part 1
Nutrients - Macronutrients
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3.1 Nutrients - Micronutrients
Chapter 3
Section 1 Part 2
Nutrients - Micronutrients
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3.1 Nutrients - Micronutrients
Micronutrients: nutrients that are needed in
small quantities
Types of Micronutrients
 Vitamins
 Minerals
 Antioxidants
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3.1 Nutrients - Micronutrients
Vitamins: usually function as coenzymes –
required for enzymes to function
 Vitamin D the only one we can synthesize
 All other vitamins must come from food
 Some are water-soluble, some are fatsoluble
 See Table 3-1 for vitamins & their functions
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3.1 Nutrients - Micronutrients
See Table 3-1
for vitamins
& their
functions
Water soluble
vitamins ->
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3.1 Nutrients - Micronutrients
See Table 3-1
for vitamins
& their
functions
Fat soluable
vitamins ->
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3.1 Nutrients - Micronutrients
Minerals: don’t contain carbon – inorganic
 Examples: calcium, iron, magnesium,
phosphorus, potassium, sulfur and sodium
 Water-soluble
 Function in:
 water balance,
 muscle and nerve function
 As co-enzymes
 See Table 3-2 for minerals & their functions
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3.1 Nutrients - Micronutrients
See Table 3-2 for minerals & their functions
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3.1 Nutrients - Antioxidants
Antioxidants: play a role in prevention of
diseases such as cancer and may slow
aging
 Functions
 Antioxidants block highly reactive free
radicals from damaging cells and DNA
 Free Radical = an atom with at least one
unpaired electron; in the body it is usually an
oxygen molecule that has lost an electron
and will stabilize itself by stealing an electron
from a nearby molecule
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3.1 Nutrients - Processed Versus Whole
Foods
Antioxidants in
Food
 Help prevent
damage from
free radicals
 Table 3.3
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3.1 Nutrients - Processed Versus Whole
Foods
Processed Versus Whole Foods
 Processing can remove much of a food’s
nutrition
 Whole foods: foods not stripped of
nutrition by processing
 Rich in complex carbohydrates, vitamins,
minerals, and Antioxidants
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3.1 Nutrients - Micronutrients
Chapter 3
End of Section 1 Part 2
Nutrients - Micronutrients
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3.2 Enzymes and Metabolism
Chapter 3
Section 2
Enzymes and Metabolism
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3.2 Enzymes and Metabolism
Metabolism: all chemical reactions occurring in
the body
Enzymes: Proteins that catalyze (speed up)
chemical reactions in a cell
 Enzymes work by lowering the activation
energy needed for a reaction
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Figure 3.6
3.2 Enzymes and Metabolism
Activation energy = the energy required to start
a metabolic reaction
•Enzymes function by lowering the required
activation energy
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Figure 3.6
3.2 Enzymes and Metabolism
Activation energy (EA) = the energy required to start a
metabolic reaction
Free energy (G) = the energy in a physical system that
can be converted to do work
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3.2 Enzymes and Metabolism
How Enzymes work
 The substrate binds to enzymes “active site”
 This binding induces the enzyme to change
shape (i.e. induced fit), stressing the
chemical bonds
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Figure 3.7
3.2 Enzymes and Metabolism
 Enzymes have “specificity”
 Because the active site must be an exact fit,
only certain substrates can bind to a
particular enzyme
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Figure 3.7
3.2 Enzymes and Metabolism
PLAY
Animation—Enzymes
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3.2 Enzymes and Metabolism - Calories and
Metabolic Rate
Calories and Metabolic Rate
 Calorie: a unit of energy
 Cells consume calories from food to do work
and maintain temperature.
 Extra calories can be stored as fat.
 Metabolic rate: the rate at which the body
uses energy
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3.2 Enzymes and Metabolism - Calories and
Metabolic Rate
 Basal metabolic rate =
metabolic rate of a resting,
alert individual
 ~ 1680 Calories/day
 Metabolic rate is influenced
by many factors:




Body weight
Exercise
Sex
Genetic makeup
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3.2 Enzymes and Metabolism
Chapter 3
End Section 2
Enzymes and Metabolism
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3.3 Transport Across Membranes
Chapter 3
Section 3
Transport Across Membranes
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3.3 Transport Across Membranes
 Food must be digested and transported
into cells
 To do so nutrients must get across the
plasma membrane
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Figure 3.9
3.3 Transport Across Membranes
Plasma membrane is differentially
permeable: allows some molecules
across, blocks others.
Materials can move across membrane by:
 Passive transport – no energy required
 Active transport – required energy input
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3.3 Transport Across Membranes
 Passive transport: diffusion of small,
hydrophobic molecules across the
membrane
Occurs by
 Simple Diffusion
 Osmosis
 Facilitated diffusion
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Figure 3.11a
3.3 Transport Across Membranes
Types of Passive Transport
 Diffusion: movement of molecules from
area of high concentration to low
concentration (down conc. gradient)
 No input of energy required
 Continues until equilibrium reached
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3.3 Transport Across Membranes
Types of Passive Transport
 Osmosis: diffusion of water across a
membrane, from high to low concentration.
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Figure 3.11c–d
3.3 Transport Across Membranes
Types of Passive Transport
 Facilitated diffusion: transport of
hydrophilic and charged molecules across
the membrane.
 Uses protein
channels embedded
in the membrane
 No input of energy
required
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Figure 3.11b
3.3 Transport Across Membranes
Active transport
 Uses proteins to move molecules from low to
high concentration
 Powered by energy from ATP
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3.3 Transport Across Membranes
PLAY
Animation—Passive and Active Transport
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3.3 Transport Across Membranes
Transport of large molecules
 Large molecules cannot get across the
membrane by diffusion or with the help of a
protein.
Use 2 mechanisms
 Exocytosis
 Endocytosis
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3.3 Transport Across Membranes
 Exocytosis: a membrane-bound vesicle
fuses with the membrane and expels the
large molecule
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3.3 Transport Across Membranes
 Endocytosis: a vesicle forms around a
large molecule and brings it into the cell
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3.3 Transport Across Membranes
PLAY
Animation—Exocytosis and Endocytosis
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3.3 Transport Across Membranes
Chapter 3
End Section 3
Transport Across Membranes
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3.4 Body Fat and Health
Chapter 3
Section 4
Body Fat and Health
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3.4 Body Fat and Health
Who is overweight?
 Difficult to define “overweight” precisely
 Women need more body fat to maintain
fertility than men do
 Healthy body fat percentages:
 Women: 22% (range 12-32%)
 Men: 14% (range 3-29%)
 But percent body fat is hard to measure
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3.4 Body Fat and Health
Body Mass Index (BMI): correlates amount
of body fat with risk of illness and death,
using both height and weight
 Not perfect!
 Does not account for frame size, gender
or muscle mass
 Healthy range of BMI = 20-25
 Obesity: BMI of 30 or higher
 1 in 3 American is obese
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3.4 Body Fat and Health
 Body Mass Index (BMI
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3.4 Body Fat and Health
Obesity and Life Style
EXP: Pima Indians
 Pima tribe split several hundred years ago
 Arizona Pima adopted American life style
 High fat, low fiber diet
 Little exercise
 60% of population obese with diabetes
 Mexican Pima retained traditional life style
 Low fat, high fiber diet of fruits & vegetables
 Lot of exercise from farming
 Diabetes is almost unheard of
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3.4 Body Fat and Health
Obesity and disease
 Risk of obesity is influenced by both
lifestyle (diet, exercise) and genetics
 Obesity increases risks of:





Diabetes
Hypertension (high blood pressure)
Heart disease
Stroke
Joint problems
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3.4 Body Fat and Health
 Diabetes: caused by lack of insulin or
inability to respond to insulin
 Insulin: hormone that triggers cells to take
up glucose; produced by beta cells of the
pancreas
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Figure 3.16
3.4 Body Fat and Health
 Diabetes: without insulin, cells can not
uptake glucose.
1. cells cannot use it for metabolism
2. glucose builds up in the blood
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Figure 3.16
3.4 Body Fat and Health
Types of Diabetes
 Type 1 (insulin-dependent)




Not associated with obesity
Usually arises in childhood
Cannot produce insulin (no beta cells)
Treated with daily insulin injections
 Type 2 (non-insulin-dependent)
 Associated with obesity
 Usually arises in adults
 May be controlled by diet and exercise
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3.4 Body Fat and Health
Hypertension: high blood pressure (the
force exerted on blood vessels by the
blood)
 Systolic: blood pressure as the heart
contracts
 Diastolic: blood pressure while heart is
relaxing
 Normal blood pressure is about 120 systolic
and 80 diastolic (120/80)
 Hypertension: persistently over 140/90
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3.4 Body Fat and Health
Hypertension:
 The increased tissue from obesity needs
blood flow to supply oxygen & nutrients
 More blood and more blood vessels
means the heart must pump harder, and
at greater pressure to keep blood flowing
 Hypertensive people are 6 times more likely
to have a heart attack
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3.4 Body Fat and Health
Heart attack: a sudden loss of blood to the
heart because of blocked arteries
Stroke: a sudden loss of blood to the brain
because of blocked or ruptured arteries
 Heart attack & stroke are more likely in
obese people as high blood pressure
damages the artery walls, allowing
cholesterol to be deposited
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3.4 Body Fat and Health
Cholesterol: a lipid that can build up in
arteries, eventually blocking them
(atherosclerosis).
 Some cholesterol is needed to build
plasma membranes and steroid hormones
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Figure 3.17
3.4 Body Fat and Health
 Cholesterol is carried in the blood by
lipoproteins
 Low-density lipoproteins (LDLs or bad
cholesterol): carry cholesterol made in the
liver and from foods
 High-density lipoproteins (HDLs or good
cholesterol): carry excess cholesterol to the
liver, for excretion as bile
 Saturated fats may raise cholesterol levels
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3.4 Body Fat and Health
Eating Disorders
 Anorexia: self-starvation
 Can starve heart muscles,
producing altered rhythms
 Amenorrhea: cessation of
menstruation; can be
permanent and result in
sterility
 Increases risk of
osteoporosis
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3.4 Body Fat and Health
Eating Disorders
 Bulimia: binge-eating followed by purging




Many of the same health effects as anorexia
May lead to stomach rupture
Dental and gum problems from stomach acid
Dehydration (sometimes fatal)
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3.4 Body Fat and Health
Eating Disorders Summary
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3.4 Body Fat and Health
Summary
 Fitness may be more important than
weight
 Fit but overweight people are healthier
than unfit slender people
 Key is healthy diet and exercise
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Chapter 3
END Chapter 3
Diet
Cells and Metabolism
Copyright © 2010 Pearson Education, Inc.