Transcript VGCSE Health and Social Care Unit 2

Biological Molecules
Carbohydrates
(CHO) e.g.
Starch, Glucose,
Sucrose
Importance of
Water &
Inorganic Ions
What you need
to learn…
Biological Tests
– chemical testing
for present of
these molecules
Lipids/Fats
(CHO), e.g.
Saturated,
Unsaturated,
Triglycerides
Proteins (CHON),
e.g. Enzymes,
Hormones,
Antibodies
The Importance of Water
Water is vital to all living organisms, it makes up 80% of cells, is
used in transporting substances, is needed for metabolic
reactions (like R/P) and helps with temperature control.
Properties of Water:
Polar – the negatively charged Oxygen atom and positively
charged Hydrogen atoms
Cohesion – the negative & positive ends of water molecules
cause them to attract to each other and form Hydrogen bonds
(H bonds)
High Surface Tension – acts like it has a skin
High Specific Heat Capacity – it takes a lot of energy to heat it
up (amount of energy needed to raise 1g by 1°C)
High Latent Heat – needs a lot of heat energy to evaporate it
Maximum Density at 4°C – means ice floats (less dense than
liquid form)
Water’s Polarity makes it a Good Solvent
http://www.northland.cc.mn.us/biology/Biology111
Click to see water in motion!
1/animations/hydrogenbonds.html
Salt (Sodium Chloride)
dissolving in water:
Hydrogen
atoms
Oxygen
atom
What molecules are foods made of?
There are three main types of food molecules.
 Carbohydrates are chains of
repeating molecules of glucose
and other sugars.
 Proteins are chains of different
amino acids.
 Fats are made up of lipids. A lipid
has a structure of three fatty acid
molecules and a glycerol molecule.
Food also contains vitamins and minerals, which are
needed in small amounts for a healthy body.
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/index.shtml
Carbohydrates
Carbohydrates are compounds of Carbon, Hydrogen and Oxygen. They
are the source of energy in all living things and can add strength and
support to cell membranes & cell walls.
Monosaccharides
(M/S)
• (or Simple sugars)
• All carbohydrates
are made of sugar
molecules.
• A single sugar
molecule is called a
monosaccharide
• E.g. Glucose,
Fructose, Ribose
•
Disaccharides (D/S)
Formed when two M/S
join together
• Occurs during a
CONDENSATION REACTION
– where a water molecule
is released
• The link between the two
sugar molecules is called
a GLYCOSIDIC BOND.
• E.g. Sucrose, Maltose,
Lactose
Polysaccharides (P/S)
• Made up of
hundreds of M/S
joined together
• Long chains of M/S
are joined by
glycosidic bonds
• P/S can be
branched or
unbranched.
• E.g. Starch,
Cellulose, Glycogen
Monosaccharides (M/S)
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/15monosaccharides/index.shtml
-glucose
Or more simply…
-glucose
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/16disaccharides/index.shtml
Disaccharides (D/S)
Examples of Disaccharides
Sucrose: glucose + fructose,
Lactose: glucose + galactose,
Maltose: glucose + glucose.
Sucrose is used in many plants for transporting food
reserves, often from the leaves to other parts of the plant.
Lactose is the sugar found in the milk of mammals and
maltose is the first product of starch digestion and is
further broken down to glucose before absorption in the
human gut.
Polysaccharides
Polysaccharide:
Function:
Structure:
Starch
Main storage
polysaccharide in
plants.
Made of 2 polymers - amylose and
amylopectin.
Amylose: a long unbranched chain of
alpha-glucose. The angles of the
glycosidic bonds give it a coiled
structure (also called a helix)
Amylopectin: a long branched chain of
alpha-glucose. Its side branches make it
particularly good for the storage of
glucose.
Relationship of
structure to function:
Insoluble therefore good for
storage.
Helix is compact and good
for storage.
The branches mean that the
enzymes can get to the
glycosidic bonds easily to
break them & release the
glucose.
Glycogen
Main storage
polysaccharide in
animals and
fungi
Similar to amylopectin but with many
more branches which are also shorter.
The number and length of
the branches means that it is
extremely compact and very
fast hydrolysis.
Cellulose
Main structural
component of
plant cell walls
Adjacent chains of long, unbranched
polymers of glucose joined by b-1,4glycosidic bonds hydrogen bond with
each other to form microfibrils.
The microfibrils are strong
and so are structurally
important in plant cell walls.
What they look like…
Starch
(Amylose)
(Amylopectin)
Cellulose
Glycogen
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/03lipids/index.shtml
Lipids
Lipids are made up of the elements Carbon,
Hydrogen and Oxygen but in different
proportions to carbohydrates (less O2). The
most common type of lipid is the triglyceride.
Lipids can exist as fats, oils and waxes. Fats and
oils are very similar in structure (triglycerides).
• At room temperature, fats are solids and oils are
liquids. Fats are of animal origin, while oils tend
to be found in plants.
• Waxes have a different structure (esters of fatty
acids with long chain alcohols) and can be
found in both animals and plants.
Functions of Lipids
1.
2.
3.
4.
5.
6.
7.
8.
9.
High-energy store - they have a high proportion of H atoms
relative to O atoms and so yield almost twice as much energy
than the same mass of carbohydrate.
Thermal insulation - fat conducts heat very slowly so having a
layer under the skin (adipose tissue) keeps metabolic heat in.
Shock absorption – acts as a cushion against blows (to organs)
Buoyancy - as lipids float on water, they can have a role in
maintaining buoyancy in organisms.
Storage - lipids are non-polar and so are insoluble in water, so can be
stored/localised in animals.
Production of water - some water is produced as a final result of
respiration.
Electrical insulation - the myelin sheath around axons prevents ion
leakage.
Waterproofing - waxy cuticles are useful, for example, to prevent excess
evaporation from the surface of a leaf.
Hormone production - steroid hormones. Oestrogen requires lipids for
its formation, as do other substances such as plant growth hormones.
Triglycerides
A triglyceride molecule is made of a glycerol
molecule and three fatty acids.
The molecules join together through the process
of condensation losing a molecule of water each
time a link is made.
Glycerol
molecule
3 Fatty
Acid Tails
How triglycerides are formed:
Fatty acids are chains of carbon atoms, the terminal one having
an OOH group attached making a carboxylic group (COOH).
The length of the chain is usually between 14 and 22
carbons long.
Three fatty acid chains become attached to a glycerol molecule
which has 3 OH groups attached to its 3 carbons.
This is called a condensation reaction because 3 water
molecules are formed from 3 OH groups from the fatty acids
chains and 3 H atoms from the glycerol.
The bond between the fatty acid chain and the glycerol is called
an ester linkage.
3 Water Molecules
are formed here
Ester links are
formed between
these atoms
A Special Type of Lipid…Phospholipids
Phospholipids are important in the formation
and functioning of cell membranes in cells.
They have a slightly different structure to
Phosphate
(hydrophilic) triglycerides:
• A phosphate group replaces one of
Glycerol
the fatty acid chains/groups
• The phosphate group is hydrophilic
(attracts water) and is polar
• The rest of the molecule (fatty acid
tails) is hydrophobic (repels water) and
non-polar
Fatty Acid tails
(hydrophobic)
Functions of proteins
1. Virtually all enzymes are proteins.
2. Structural: e.g. collagen and elastin in connective tissue,
keratin in skin, hair and nails.
3. Contractile proteins: actin and myosin in muscles allow
contraction and therefore movement.
4. Hormones (Signal Proteins): many hormones have a protein
structure (e.g. insulin, glucagon, growth hormone).
5. Transport: for example, haemoglobin facilitates the transport of
oxygen around the body, a type of albumin in the blood
transports fatty acids.
6. Transport into and out of cells: carrier and channel proteins in
the cell membrane regulate movement across it.
7. Defensive: immunoglobulins (antibodies) protect the body
against foreign invaders; fibrinogen in the blood is vital for the
clotting process.
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/index.shtml
Proteins
Proteins are amino acid polymers. Twenty different amino
acids exist naturally. These link up in different orders to form
all the many different proteins present in living organisms. All
amino acids contain four distinct chemical groups connected
to a central carbon atom:
• a single hydrogen atom
• an amino group (NH2)
• a carboxyl group (COOH)
• a side chain (this is represented by the letter R & differs in
different amino acids)
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/12polymers/index.shtml
http://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/peptide.html
Joining Amino acids Together
The amino acids in a protein are joined together by
CONDENSATION reactions and broken apart by
HYDROLYSIS reactions (just like in carbohydrates & lipids).
The bonds formed between amino acids are called
PEPTIDE bonds.
Two amino acids joined together are called a dipeptide.
http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/13structures/index.shtml
Structure of Proteins
Proteins are big complicated molecules. Their structure can be
explained in four ‘levels’. These levels are called the protein’s
PRIMARY, SECONDARY, TERTIARY and QUATERNARY
structures.
The primary structure
is the sequence of the
amino acids in the long
chain that makes up the
protein (the polypeptide
chain)
Secondary Structure
Chains of amino acids (polypeptides) can form
coils (α-helix) or pleats (β-pleated sheets).
This coiling or pleating is called the proteins’
secondary structure. The secondary structure is
held together by Hydrogen bonds.
Tertiary Structure
Long polypeptide chains often fold and are joined
by additional, weak chemical (ionic) bonds that
give the protein a complex 3-dimensonal shape.
This is the tertiary structure.
Quaternary Structure
Finally, some proteins are made of several different
polypeptide chains held together by various
bonds. The quaternary structure is the way these
different parts are assembled together.
Types of bonds:
The shape of the protein is held together by Hydrogen bonds
between some of the R groups (side chains) and Ionic bonds
between positively and negatively charged side chains. These are
weak interactions, but together they help give the protein a stable
shape. The protein may be reinforced by strong covalent bonds
called Disulphide bridges which form between two amino acids
with sulphur groups on their side chains (cysteine).
Hydrophobic bonds form when water-repelling hydrophobic groups
are close together in the protein & tend to clump together
Each protein formed has a precise and specific shape.
Protein Shape Relates to Function
Fibrous proteins are made of long molecules arranged to form
fibres (e.g. in keratin). Several helices may be wound around each
other to form very strong fibres. Collagen is another fibrous
protein, which has a greater tensile strength than steel because it
consists of three polypeptide chains coiled round each other in a
triple helix. We are largely held together by collagen as it is found
in bones, cartilage, tendons and ligaments. Insoluble in H2O.
Globular proteins are made of chains folded into a compact
structure. One of the most important classes are the enzymes.
AAlthough
globular these
proteinfolds
based
on an -helix
haemoglobin.
aremostly
less regular
than in aishelix,
they are Its
highly specific
protein
willattracting)
always beside
folded
in the
structure
is curledand
up, asoparticular
hydrophilic
(water
chains
are
way toofform
a roughly and
spherical
molecule.
If the
structureside
is
onsame
the outside
the molecule
hydrophobic
(water
repelling)
disrupted,
the protein
ceases
said to be
chains
face inwards.
This
makestoitfunction
soluble properly
and goodand
for is
transport
in
denatured. An example is insulin, a hormone produced by the
blood,
pancreas and involved in blood
sugar regulation. Soluble in H2O.
Inorganic Ions in Living Things
Many inorganic ions that can dissolve in water are important
in the metabolism of organisms.
Remember: ions = charged particles
Inorganic ions = ions that don’t contain Carbon
ION
IMPORTANT USE
Calcium (Ca2+)
For forming Bones
Sodium (Na2+)
Involved in Nerve transmission
Potassium (K+)
Activates enzymes
Magnesium (Mg2+)
Contained in Chlorophyll
Chloride (Cl-)
Produces hydrochloric Acid (HCl) in Stomach
Nitrate (NO3-)
Makes Proteins in Plants
Phosphate (PO43-)
Needed for ATP production