Carbohydrates (CHO) e.g.

Starch, Glucose, Sucrose

Lipids/Fats (CHO), e.g. Saturated,

Unsaturated, Triglycerides

Proteins (CHON), e.g. Enzymes,

Hormones, Antibodies

Biological Tests – chemical testing

for present of these molecules

Biological Molecules

What you need to learn…

Importance of Water &

Inorganic Ions

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 skinHigh 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

Salt (Sodium Chloride) dissolving in water:

Oxygen atom

Hydrogen atoms

http://www.northland.cc.mn.us/biology/Biology1111/animations/hydrogenbonds.html

Click to see water in motion!

What molecules are foods made of?

There are three main types of food molecules.

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.

Carbohydrates are chains of repeating molecules of glucose and other sugars.

Food also contains vitamins and minerals, which areneeded in small amounts for a healthy body.

Carbohydrates

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

• 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

• 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

Disaccharides (D/S) Polysaccharides (P/S)

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.

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/index.shtml

Monosaccharides (M/S)

-glucose -glucose

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/15monosaccharides/index.shtml

Or more simply…

Disaccharides (D/S)

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/02carbohydrates/16disaccharides/index.shtml

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.

PolysaccharidesPoly-saccharide:

Function: Structure: Relationship of structure to function:

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.

 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-1,4-glycosidic 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…

(Amylose)

(Amylopectin)Cellulose

Starch

Glycogen

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.

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/03lipids/index.shtml

Functions of Lipids

1. 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.

2. Thermal insulation - fat conducts heat very slowly so having a layer under the skin (adipose tissue) keeps metabolic heat in.

3. Shock absorption – acts as a cushion against blows (to organs)4. Buoyancy - as lipids float on water, they can have a role in

maintaining buoyancy in organisms.

5. Storage - lipids are non-polar and so are insoluble in water, so can be stored/localised in animals.

6. Production of water - some water is produced as a final result of respiration.

7. Electrical insulation - the myelin sheath around axons prevents ion leakage.

8. Waterproofing - waxy cuticles are useful, for example, to prevent excess evaporation from the surface of a leaf.

9. 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 triglycerides:

• A phosphate group replaces one of 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

Glycerol

Fatty Acid tails (hydrophobic)

Phosphate (hydrophilic)

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.

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/index.shtml

Joining Amino acids TogetherThe 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/12polymers/index.shtml

http://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/peptide.html

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)

http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/13structures/index.shtml

Secondary StructureChains 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. Although these folds are less regular than in a helix, they are highly specific and a particular protein will always be folded in the same way to form a roughly spherical molecule. If the structure is disrupted, the protein ceases to function properly and is said to be denatured. An example is insulin, a hormone produced by the pancreas and involved in blood sugar regulation. Soluble in H2O.

A globular protein based mostly on an -helix is haemoglobin. Its structure is curled up, so hydrophilic (water attracting) side chains are on the outside of the molecule and hydrophobic (water repelling) side chains face inwards. This makes it soluble and good for transport in

blood,

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