Download Lipids

Happy 2nd Birthday Tavis!
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Macromolecules!
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You are what you eat
• These macromolecules are the main
components of the cells of the body.
• Food comes from other living things that
are also made up of cells.
• The digestive system makes the small
building blocks of these molecules
available to cells for use as energy or as
materials for growth and repair.
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You are what you eat!
When food is digested its components enter the blood.
carbohydrate
glucose
fat
fatty acids
+ glycerol
protein
amino acids
Molecules used for growth and
repair become part of the body.
Those used as energy sources are lost as CO2 and H2O.
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What are cells made from?
Different nutrients are incorporated into each part of a cell:
nucleus:
protein
membrane:
fats and
carbohydrate
cytoplasm:
protein and
water
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Different nutrients
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Chemical and physical digestion
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Enzymes at work
Enzymes digest food in the mouth, stomach and small
intestine.
Enzymes break
down large food
molecules into
smaller ones that
can be absorbed by
the blood. This is
called chemical
digestion.
Different types of food are broken down by different enzymes.
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Enzymes of digestion
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Introduction to lipids
Lipids are a diverse group of compounds that are insoluble
in water but soluble in organic solvents such as ethanol.
The most common
types of lipid are
triglycerides (sometimes
known as true fats or
neutral fats), but other
important lipids include
waxes, steroids and
cholesterol.
Like carbohydrates, lipids contain carbon, hydrogen and
oxygen, but they have a high proportion of hydrogen
and a lower proportion of oxygen.
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Role of lipids
The major biological role of lipids is as an energy source.
Lipids provide more than twice the amount of energy as
carbohydrates – about 38 kJ/g.
Lipids are stored in adipose
tissue, which has several
important roles, including:

heat insulation – in
mammals, adipose tissue
underneath the skin
helps reduce heat loss.

protection – adipose tissue around delicate organs such
as the kidneys acts as a cushion against impacts.
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The structure of triglycerides
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Saturated and unsaturated
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The structure of phospholipids
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Introducing proteins
Proteins are a diverse group of large and complex polymer
molecules, made up of long chains of amino acids.
They have a wide range of biological roles, including:

structural: proteins are the
main component of body
tissues, such as muscle,
skin, ligaments and hair

catalytic: all enzymes are
proteins, catalyzing many
biochemical reactions

signalling: many hormones and receptors are proteins

immunological: all antibodies are proteins.
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The general structure of amino acids
All amino acids have the same general structure: the only
difference between each one is the nature of the R group.
So the R group defines an amino acid.
amino
group
carboxylic
acid group
R group
The R group represents a side chain from the central “alpha”
carbon atom, and can be anything from a simple hydrogen
atom to a more complex ring structure.
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The 20 naturally occurring amino acids
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Peptide bonds and dipeptides
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Polypeptides
When more amino acids
are added to a dipeptide,
a polypeptide chain is
formed.
A protein consists of
one or more polypeptide
chains folded into a
highly specific 3D
shape.
There are up to four levels of structure in a protein: primary,
secondary, tertiary and quaternary. Each of these play an
important role in the overall structure and function of the
protein.
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Globular proteins
Globular proteins usually have a spherical shape caused
by tightly folded polypeptide chains.
The chains are usually folded so that hydrophobic groups are
on the inside, while the hydrophilic groups are on the outside.
This makes many globular proteins soluble in water.

transport proteins – such
as hemoglobin, myoglobin
and those embedded in
membranes.

enzymes – such as lipase
and DNA polymerase.

hormones – such as
estrogen and insulin.
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Introducing carbohydrates
Carbohydrates are a group of substances used as both
energy sources and structural materials in organisms.
All carbohydrates contain carbon, hydrogen and oxygen,
with the general formula: Cx(H2O)y.
There are three main groups of carbohydrates:

monosaccharides – these are simple sugars, with the
general formula (CH20)n, where n can be 3–7

disaccharides – these are “double sugars”, formed
from two monosaccharides

polysaccharides – these are large molecules formed
from many monosaccharides.
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Glucose
Glucose is an abundant and very important monosaccharide.
It contains six carbon atoms, so it is a hexose sugar. Its
general formula is C6H12O6.
Glucose is the major energy source for most cells. It is
highly soluble and is the main form in which carbohydrates
are transported around the body of animals.
The structure of glucose can be represented in different ways:
straight chain
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ring
ring (simplified)
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Fructose and galactose
Two other important hexose monosaccharides are fructose
and galactose.
fructose
galactose
Fructose is very soluble and is the main sugar in fruits and
nectar. It is sweeter than glucose.
Galactose is not as soluble as glucose and has an important
role in the production of glycolipids and glycoproteins.
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The formation of disaccharides
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Disaccharides
Maltose (malt sugar) is
formed from two glucose
molecules joined by an
alpha 1–4 glycosidic bond.
Sucrose (table sugar) is
formed from glucose and
fructose joined by an
alpha 1–4 glycosidic bond.
Lactose (milk sugar) is
formed from galactose
and glucose joined by a
beta 1–4 glycosidic bond.
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What are polysaccharides?
Polysaccharides are polymers containing many
monosaccharides linked by glycosidic bonds. Like
disaccharides, polysaccharides are formed by
condensation reactions.
Polysaccharides are mainly used as an energy store and as
structural components of cells.
The major polysaccharides are starch and cellulose in
plants, and glycogen in animals.
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The structure of starch
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Properties and uses of starch
Starch is the major carbohydrate storage molecule in plants.
It is usually stored as
intracellular starch
grains in organelles
called plastids.
Plastids include green
chloroplasts (e.g. in
leaves) and colorless
amyloplasts (e.g. in
potatoes).
Starch is produced from glucose made during photosynthesis.
It is broken down during respiration to provide energy and is
also a source of carbon for producing other molecules.
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What is cellulose?
Cellulose is another polysaccharide and is the main part of
plant cell walls. It is the most abundant organic polymer.
Unlike starch, cellulose is very strong, and prevents cells
from bursting when they take in excess water.
Cellulose consists of long
chains of beta glucose
molecules joined by beta
1–4 glycosidic bonds.
The glucose chains form
rope-like microfibrils,
which are layered to form
a network.
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What is glycogen?
Animals do not store carbohydrate as starch but as glycogen.
Glycogen has a similar
structure to amylopectin,
containing many alpha 1–6
glycosidic bonds that produce an
even more branched structure.
Glycogen is stored as small
granules, particularly in
muscles and liver.
Glycogen is less dense and more soluble than starch, and is
broken down more rapidly. This indicates that animals have
higher metabolic requirements than plants.
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