Download 1.3.1 Function of Food

1.3.1 Function of Food
Why do we need food?
What you will learn
(1)Why we need food
(2)Chemical elements in food
(3)Biomolecules – carbohydrates, proteins, fats,
minerals, vitamins
(4)Structure and function of biomolecules
(5)Metabolism – anabolism and catabolism
(6)Water and its properties
Food is needed for:
1.
Energy
2.
Growth of new cells and
Repair of existing cells, tissues, organs, etc.
3
Food also supplies:
the materials and energy for the processes of:
1.
Metabolism and
2.
Continuity
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Learning check
Why do we need food?
Energy
Growth of new cells and
Repair of existing cells, tissues, organs, etc.
What is metabolism?
Metabolism is the chemical reactions that occur in the cells of
living organisms
What is continuity?
Continuity of life is the ability of an organism to exist from
generation to the next
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Need to know
● The Function of Food
● Three reasons for requiring food
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1.3.2 Chemical Elements
Elements in Food
What is Food made up of?
Food is made up of:
• Six chemical elements
C, H, O, N, P, S
• Salts of
Na, Mg, Cl, K, Ca
• Three trace elements
Fe, Cu, Zn
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Chemical Elements and their Symbols
Calcium
Ca
Nitrogen
N
Carbon
C
Oxygen
O
Chlorine
Cl
Phosphorus
P
Copper
Cu
Potassium
K
Hydrogen
H
Sodium
Na
Iron
Fe
Sulphur
S
Magnesium
Mg
Zinc
Zn
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Need to know
● Chemical elements
● Six common elements in food
● Five elements in dissolved salts
● Three trace elements
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Types of food (biomolecular structures)
Types of Food
The elements combine in different ratios to
form different food components
(biomolecular units)
Food is made up of six different components
Water
Proteins
Lipids
Carbohydrates
Vitamins
Minerals
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Humans are mainly made up of
Water!
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Carbohydrates
Carbohydrates contain the elements
Carbon
Hydrogen
Oxygen
The general formula for a carbohydrate is
Cx(H2O)y
There are twice as many hydrogen molecules as
oxygen molecules
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Learning check
What are the six different food components?
Water
Proteins
Lipids
Carbohydrates
Vitamins
Minerals
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A common carbohydrate
General formula = Cx(H2O)y
When x = y = 6
We fet the formula C6H12O6
What is the name of this monosaccharide
carbohydrate?
Glucose
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Another common carbohydrate
General formula = Cx(H2O)y
When x = 12 and y = 11
We get the formula C12H22O11
What is the name of this disaccharide
carbohydrate?
Sucrose
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Learning check
Name the three elements that make up
carbohydrates
Carbon
Hydrogen
Oxygen
What is the general formula for a carbohydrate?
Cx(H2O)y
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Need to know
● Define Biomolecular Structures
● State that simple biomolecular units are
composed of a combination of elements in
different ratios e.g. carbohydrates Cx(H2O)y
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1.3.4 Biomolecular Sources and the
Components of Food
Carbohydrates
Carbohydrates contain the elements
Carbon
Hydrogen
Oxygen
Usually in the ratio of 1C:2H:1O
They have twice as many hydrogen molecules as
oxygen molecules
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3 Types of Carbohydrate
Monosaccharides
Disaccharides
Polysaccharides
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Monosaccharides
C
These are
single sugar molecules
C
simple sugars
C
soluble in water
C
sweet to taste
smallest carbohydrate unit
Examples:
Found in:
glucose, fructose
fruit
O
C
C
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Learning check
What are the elements that make up all
carbohydrates?
Carbon
Hydrogen
Oxygen
Can you remember the general formula for a
carbohydrate?
Cx(H2O)y
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Disaccharides
These are
• two monosaccharide sugar units joined together –
known as double sugar molecules
• soluble in water
• sweet to taste
Examples:
Found in:
sucrose, lactose, maltose
table sugar, milk
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Polysaccharides
These are
• Many monosaccharide sugar molecules
joined together
• Not soluble in water
• Do not taste sweet
Example: starch, cellulose
Found in: bread, pasta, cereals
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Learning check
Name the three types of carbohydrate
● Monosaccharides
● Disaccharides
● Polysaccharides
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Lipids
Lipids are a diverse group of substances
which include
• fats (solid at room temp.)
• oils (liquid at room temp.)
• steroids which include cholesterol and
some of the sex hormones
• waxes which cover insect bodies and plant
leaves.
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Structure of Lipids
They are made up of the elements
carbon
hydrogen
oxygen
But not have the same ratios as carbohydrates.
They are made up of two main types of molecules
Fatty acids and
Glycerol
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Learning check
Give examples and sources of:
Examples
Monosaccharides
Disaccharides
Polysaccharides
Glucose
Sources
fruit
Fructose
Sucrose
Table sugar
Lactose
Starch
Milk
Bread, Pasta,
Cellulose
Cereals
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Types of Lipid
Two of the main types of lipids are
Triglycerides
Phospholipids
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Triglyceride
This is the smallest lipid
It is made up of
3 fatty acid molecules
and
1 glycerol molecule
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Phospholipids
If one fatty acid of a lipid molecule is replaced
by a phosphate group then a phospholipid is
formed
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Sources of Lipids
● Fat – in and on meat
● Butter (80% fat)
● Cooking oils
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Learning check
The two main types of molecules that make
up lipids are:
Fatty acids and
Glycerol
The two main types of lipids are:
Triglycerides
Phospholipids
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Proteins
Proteins contain the elements
Carbon
Hydrogen
Oxygen
Nitrogen
Some may also contain sulphur, phosphorous
or iron
Proteins are found in lean meat, fish, pulses,
soya and eggs
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Structure of Proteins
Proteins are made up of long chains of
amino acids
There are 20 common and several rare amino
acids found in proteins
More amino acids are found in cells and tissues
but are not in proteins
Amino acids are joined together by
peptide bonds
This results in the formation of polypeptide chains
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Amino Acids
All amino acids contain four distinct chemical
groups connected to a central carbon atom:
● a single hydrogen atom
● an amino group
● a carboxyl group
● a side chain
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Learning check
Proteins contain the elements
Carbon
Hydrogen
Oxygen
Nitrogen
Sometimes they contain
sulphur, phosphorous or iron
Proteins are made up of long chains of
amino acids
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Vitamins
Vitamins are essential organic catalysts of
metabolism
● Needed in small amounts, cannot be
produced in the body
● Must be supplied continuously and in
sufficient quantities
● Differ from each other chemically
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Vitamins
We need Vitamins A, B, C, D, E and K in our
diets to keep us healthy
Vitamins can be water soluble or fat soluble
Vitamins B and C are water soluble
Vitamins A, D, E and K are fat soluble
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Sources of Vitamins
Vitamin
Source
A
Green leafy vegetables, Eggs, Cheese,
Carrots
B
Lean Meat, Cereals, Nuts
C
Citrus Fruits, Green vegetables, Turnips
D
Milk and Milk products, Sunlight
E
Vegetable oils, fish, nuts
K
Green leafy vegetables
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Learning check
What is a vitamin?
A vitamin is an essential organic catalyst of
metabolism
What vitamins dissolve in water?
B&C
What vitamins are fat-soluble?
A, D, E and K
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Need to know
● State that simple bio molecular units are
composed of a combination of elements in different
ratios e.g. carbohydrates Cx(H2O)y
● Name the element components, bio molecular
components and sources of: carbohydrates, lipids
and proteins.
● State that carbohydrates are composed of
indivisible units and give examples of these e.g.
– Monosaccharides – glucose;
– Disaccharides – maltose; &
– Polysaccharides – starch/cellulose.
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Need to know
● What is a vitamin?
● Name one water soluble vitamin.
● Name one water in-soluble vitamin (fatsoluble)
● List the sources of these vitamins
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1.3.5 Energy Transfer Reactions
Anabolic & Catabolic
Or
Anabolism & Catabolism
Anabolic Reactions
This is where energy is used to make large molecules
(e.g. C6H12O6) from smaller ones (e.g. CO2 and H2O)
using enzymes
e.g. Photosynthesis – glucose molecules are formed from
carbon dioxide and water using enzymes and the energy
from the sun.
This is anabolism. Energy is absorbed.
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An Anabolic Reaction
Energy being used to join two small molecules to make a
larger molecule
Small molecule
Small molecule
ENERGY
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Larger molecule
Catabolic Reactions
This is where energy is released when large molecules
(e.g. C6H12O6) are broken down to form smaller ones
(e.g. CO2 and H2O) using enzymes
e.g. Respiration – glucose molecules are broken down by
enzymes to form carbon dioxide and water and energy is
released.
This is catabolism. Energy is released.
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Learning check
Explain Anabolism
Energy absorbed. Small  large molecules
Give an example of an anabolic reaction
Photosynthesis
Explain Catabolism
Energy released. Large  small molecules
Give an example of a catabolic reaction
Respiration
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Is catabolism the opposite of anabolism?
In the examples just given the chemical processes
(pathways*) involved in each of them are different,
therefore catabolism is not the opposite of anabolism.
* e.g. if you travel from A to B – you followed a certain
pathway. On the return journey you may come home
through C – you followed a different pathway.
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Energy Transfer Reactions
Respiration – Catabolic reaction
C6H12O6 + Oxygen  Energy + CO2 + H2O
release
Photosynthesis – Anabolic reaction
CO2 + H2O + Energy  C6H12O6 + Oxygen
absorbed
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Learning check
Is anabolism the opposite of catabolism ?
No
Why?
Different chemical pathways involved in both.
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Need to know
Definition of the terms:
Anabolic
Catabolic
Give an example of each
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1.3.6 Structural Role of
Biomolecules
What does the ‘Structural Role of
Biomolecules’ mean?
Structure = the way in which something is
built e.g. timber structure, steel structure
Role = function/job or position
Biomolecules = carbohydrates, fats, proteins
Structural Role of Biomolecules = the
function/job of carbohydrates, fats, proteins
in making various parts of living things
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Structural role of Carbohydrate
Cell Structure
 Cellulose (polysaccharide)
found in plant cell walls

Chitin (polysaccharide)
found in fungal cell walls
and insect exoskeletons
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Structural role of Proteins
Cell structure
 Proteins are fibrous (threadlike) in nature.
 They combine with phospholipids to from
cell membranes (lipoproteins)
• Keratin is the structural protein in skin, hair
and nails
• Myosin is the structural protein in muscle
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Learning check
What does the ‘Structural Role of Biomolecules’
mean?
Structural Role of Biomolecules = the function /
job of carbohydrates, fats, proteins in making
various parts of living things
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Structural role of Lipids
Cell Structure
• Important storage molecules in organisms
• Heat insulation – e.g. under the skin
• Waterproof the body
• Protection around body organs e.g. kidney,
heart
• Phospholipids and lipoproteins are major
components in cell membranes
• Myelin helps transmit messages in60nerve cells
Learning check
What is the structural role of proteins?
 Proteins are fibrous (threadlike) in nature.
 They combine with phospholipids to from
cell membranes (lipoproteins)
• Keratin is the structural protein in skin, hair
and nails
• Myosin is the structural protein in muscle
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Need to know
Structural Role of Biomolecules
 State carbohydrates role as cellulose in cell
walls
 State proteins role as fibrous protein e.g.
keratin or as myosin
 State the role of lipids as Phospholipids in
cell membranes

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1.3.8 Minerals
Minerals
What are minerals?
They are salts formed from the earth’s rocks.
These mineral salts then dissolve in water and
are absorbed by plants.
Animals get their minerals by eating plants or
other animals that contain them.
NB Minerals are required by organisms in
very small amounts.
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Minerals and Plants
Plants absorb minerals through their roots.
They use:
• Calcium (Ca) to make cell walls
• Magnesium (Mg) to make the pigment
chlorophyll
• Nitrates (N) to make proteins
• Phosphates (P) to make ATP, DNA
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Minerals and Animals
Animals get their minerals in the food they eat.
They use
• Calcium (Ca) to make bones and teeth
• Iron (Fe) to make the pigment haemoglobin
• Sodium (Na) for the regulation of the osmotic
balance (water content) of cells and the
blood.
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Learning check
How do plants get their minerals?
_________________________________
Plants absorb minerals through their roots
Plants use:
cell walls
• Calcium (Ca) to make ________
pigment
• Magnesium (Mg) to make the
_________
chlorophyll
_________
• Nitrates (N) to make proteins
______
ATP, DNA
• Phosphates (P) to make _________
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Learning check
How do animals get their minerals?
________________
In the food they eat
Animals use:
and teeth
• Calcium (Ca) to make bones
____________
• Iron (Fe) to make the pigment haemoglobin
__________
• Sodium (Na) for the regulation of the
osmotic balance (___________)
water content of cells and
_____________
the blood.
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Minerals Summary
They are required to:
Form part of rigid body tissues
Calcium in bones and cell walls
Form certain pigments
Iron is needed to make haemoglobin – the red
pigment of blood
Magnesium is needed to make chlorophyll –
the green pigment in plants
Regulate body fluids
Sodium balances water content in cells
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Need to know
Minerals required in small amounts
Minerals used in three ways
Form part of rigid body structures
Form soft body tissues
Function in cellular and body fluids
State the requirements & use of any 2
minerals in plants.
State the requirements & use of any 2
minerals in animals.
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1.3.9 Water
Importance of Water to Organisms
The three states of water
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Water
Cells and body fluids are made up of 70% to
95% Water
Water has physical and chemical properties
that have important effects on organisms.
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Physical properties of water
It is slow to heat up and cool down – kept at a
fairly steady temperature – helps to keep a
constant rate of metabolism.
A good absorber of energy. It absorbs a lot of
heat as it evaporates, so sweating and
transpiration cools animals and plants. This
helps to keep temperature steady.
Participates in the movement of material in
and out of cells.
Controls cell shape.
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Chemical properties of water
It is a universal solvent for transporting
substances in blood or in plants
The medium for metabolism i.e. chemical
reactions take place in it within cells
It is a reactant/product in chemical reactions
e.g. photosynthesis, respiration and digestion
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Learning check
What are the physical properties of water?
It is slow to heat up and cool down …
A good absorber of energy …
Movement of material …
Cell shape …
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Learning check
What are the chemical properties of water?
Universal solvent …
Medium for metabolism …
Reactant in chemical reactions …
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Need to know
Five good reasons why water is important for
organisms.
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1.3.7 Metabolic Role of
Biomolecules
What does the ‘Metabolic Role of
Biomolecules’ mean?
Metabolic = metabolism = all the chemical
reactions in a cell
Role = function/job or position/involvement
Biomolecules = carbohydrates, fats, proteins
Metabolic Role of Biomolecules = the
function / job / involvement of
carbohydrates, fats, proteins in the chemical
reactions in cells making various substances
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for living things
Metabolic Role of Carbohydrates
and Lipids
These are the primary sources of energy for
metabolism – e.g.
• glucose (carbohydrate) is an immediate
source of energy
• lipids are a long-term energy storage
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Metabolic Role of Carbohydrates
and Lipids
They are important in the following
processes:
Respiration – energy is released when
glucose is broken down to form carbon
dioxide and water – catabolism
Photosynthesis – glucose molecules are made
from carbon dioxide and water using the
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sun’s energy – anabolism
Metabolic Role of Proteins
All enzymes are proteins and have a folded
shape. Enzymes control the chemical
reactions in cells.
e.g. enzymes control the processes of
photosynthesis and respiration
Chlorophyll is a protein that traps the sun’s
energy during photosynthesis
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Learning check
1. Give examples of the primary sources of
energy for metabolism
Glucose & Lipids
1. Name two important metabolic pathways
and state whether they are anabolic or
catabolic
Photosynthesis – anabolic
Respiration – catabolic
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Metabolic Role of Hormones
Hormones regulate body functions
e.g. the hormone insulin controls the amount
of glucose in the blood
Oestrogen, progesterone and testosterone are
other hormones controlling human sexual
development
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Learning check
What is the metabolic role of protein?
Enzymes are proteins.
Enzymes control the processes of photosynthesis
and respiration
Chlorophyll is a protein that traps the sun’s
energy during photosynthesis
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Metabolic Role of Vitamins
Definition: can you remember it
Vitamins are essential organic catalysts of
metabolism
They are needed in small amounts for the
correct functioning of the body
They cannot be made by the body
They must be in the diet
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Vitamin C
Chemical name:
ascorbic acid
Solubility:
water soluble
Function: for building connective tissue i.e.
tissue used for attaching organs together or
for protection, e.g. skin, blood vessels,
bone, tendons, cartilage, ligaments
Source: Citrus Fruits, Green vegetables
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Vitamin D
Chemical name:
calciferol
Solubility:
fat soluble
Function: needed to absorb calcium from
food. Calcium needed for healthy teeth and
bone formation and their maintenance
Source: Dairy products, fish liver oils, egg
yolk, made by skin in sunlight
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Learning check
For the vitamins C & D give the following
Vit C
Vit D
The chemical name - Ascorbic acid Calciferol
Water soluble Fat soluble
Solubility
Function
Connective Absorb
tissue
calcium
formation
Source in the diet -
One source
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One source
Vitamin deficiency disorders
Lack of Vitamin C causes
scurvy
Symptoms: soft bleeding gums, bad and loose
teeth
Lack of Vitamin D causes
rickets in young children
Symptoms: softening of the bones of the spinal
column and bowlegs
osteomalacia in adults
Symptoms: the bones lose calcium and become
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weak – common in vegans
Need to know
State that carbohydrates & lipids act as a
primary source of energy
State that proteins act as enzymes and are
made of amino acids
State that hormones (protein) act as regulators
of metabolic activity
State that vitamin C & D are used for tissue
growth, cell production and health
maintenance
Name disorders associated with deficiency of
a water soluble and a fat-soluble vitamin
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END
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