Higher Human Biology
Unit 1: Cell Function and
Inheritance
Chapter 5:Sources of Energy
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Mrs Smith: Ch5 Sources of
Energy.
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Learning intentions.
• To compare the differences between
mono-, di- and poly-saccharides
• To examine the structure of lipids and
their various roles in cells and organisms
• To study protein degradation and their
use as an alternative respiratory
substrate
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Carbohydrates.
• Carbohydrates (e.g. Sugar, starch and
glycogen) are compounds whose
molecules all contain the chemical
elements CARBON (C), HYDROGEN (H)
and OXYGEN (O).
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Monosaccharides (single-sugar)
• This is a simple sugar.
• Made up of six-sided unit, galactose, glucose
and fructose are examples of these
• Monosaccharide's are soluble in water.
• Described as reducing sugars.
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Disaccharides (double-sugar)
• Made of two monosaccharides joined
together.
• Maltose and sucrose are
examples of disaccharides.
• Disaccharides are soluble in water.
• Maltose has reducing properties.
• Sucrose is a non-reducing sugar.
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Polysaccharides
• A polysaccharide is a carbohydrate
composed of many monosaccharide
molecules joined together.
• These molecules are all very large and
insoluble in water.
• ALL CARBOHYDRATES ARE RICH
SOURCES OF ENERGY
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Mrs Smith: Ch5 Sources of
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Starch
• This polysaccharide consists of a long chain of
glucose (>1000 monosaccharide units).
• These molecules are all very large and insoluble
in water.
• Starch is the form in which plants store
carbohydrate.
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Glycogen
• This polysaccharide is very similar to a branched
form of starch.
• These molecules are also very large and insoluble
in water.
• This means glycogen cannot diffuse out of the
cell and they do not affect the cells osmotic
balance
• This makes it an ideal storage material,
particularly abundant in liver and muscle cells.
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Mrs Smith: Ch5 Sources of
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ENERGY
• ALL CARBOHYDRATES are a rich source of
ENERGY.
• Monosaccharide's can be used to release
energy. (e.g. glucose can undergo glycolysis
during respiration)
• However disaccharides and polysaccharides
must be broken down by enzymes before they
can release their energy.
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Mrs Smith: Ch5 Sources of
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Identifying unknown carbohydrates
CARBOHY
DRATE
TEST
Solubility
Benedict’s
Barfored’s
Clinistix
Iodine
Glucose
Soluble
Brick-red
Brick-red
rapidly
Purpleblue
-
Fructose
Soluble
Brick-red
Brick-red
rapidly
-
-
Maltose
Soluble
Brick-red
Faint Brickred slowly
-
-
Lactose
Soluble
Brick-red
-
-
Sucrose
Soluble
Brick-red
after acid
hydrolysis
-
-
-
Starch
Insoluble
-
-
-
Blue-black
Glycogen
Insoluble
-
-
-
Purple-red
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TASK
• Testing your knowledge: Please complete
Torrance pg38 Qu’s 1-3.
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Lipids
• This is a diverse group of
organic compounds including
fats, oils, phospholipids and
steroids.
• Lipids contain the elements C,
H and O. (but the proportion of
oxygen in lipids is smaller than
in carbohydrates).
• LIPIDS ARE INSOLUBLE IN
WATER
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Triglyceride (Simple lipid)
• Fat (solid at rm temp) and oil (Liquid at rm
temp) are examples of triglycerides.
• Their molecular structure consists of a
glycerol and 3 fatty acids.
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Phospholipids
• A typical phospholipid contains two
molecules of fatty acids linked to one
glycerol, in addition it has one phosphate
on the third position of the glycerol
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Phospholipids- different
properties at each end!
• The phosphate (‘head’) end
of the molecule is
hydrophilic (water loving)
and is therefore soluble in
water.
• The fatty acid (‘tail’) end of
the molecule is hydrophobic
(water-hating) and is
therefore insoluble in water.
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Phospholipid example.
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Steroids
• Steroids are lipids, however their structure
varies from simple and phospholipids.
• Each molecule of a steroid has a basic
structure composed of 3 6-carbon rings joined
to a 5-carbon ring.
• Cholesterol is an example of a steroid. It provides the
basic molecular structure from which other steroids
are formed (bile and sex hormones).
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Steroids
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Roles of Lipids
•
•
•
•
•
•
Energy store
Thermal and nerve insulation
Fat pads
Vitamin transport
Hormones
Major components of the plasma
membrane
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Roles of Lipids: Energy store
• Fat is deposited in fatty (adipose) tissue.
• It is insoluble and compact making it an ideal
form in which to store energy.
• When energy is required, a fat molecule is
broken down into glycerol and fatty acids
which become available for use in aerobic
respiration.
• Fat liberates more than double the quantity
of energy than the same mass of
carbohydrate.
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Roles of Lipids: Thermal and
nerve insulation.
• The fat beneath the skin also
serves as a INSULATOR to
help conserve body heat.
• The sheath around each nerve
fibre consists of a fatty material
called myelin, this insulated the
nerve and increased the speed
of the impulses.
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Roles of Lipids: Fat Pads
• Pads of fat in the palms of the hands and
soles of the feet protect the underlying
structures by acting as cushions.
• The kidneys are also protected by fat pads.
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Roles of Lipids: Plasma
membrane
• Phospholipids are one of the
basic building blocks of cell
membranes.
• The steroid cholesterol is
also an important
components of membranes.
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Proteins
• Proteins broken down into amino acids.
• Excess amino acids cannot be stored in the
body.
• They are deaminated into urea and organic
compounds.
• These organic acids enter the respiratory
pathway to produce some ATP
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Starvation
• Tissue protein is used as a source of energy
only during prolonged starvation when the
reserves of glycogen and fat have become
exhausted.
• Skeletal muscle and other
tissues rich in protein are
used up to produce
energy during the crisis.
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Marathon Running
• In the first few minutes the body uses
glucose from muscle glycogen.
• Blood glucose mainly from liver glycogen
is used for the next 30 minutes
• As glucose supplies decrease fatty acids
become the energy supply.
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