LESSON 1-3: BiomacromoleculesLEARNING OUTCOMESBy the end of these lessons, you should be able

to:

Describe the structure and function of lipids.

Describe the structure and function of the nucleic acids; DNA and RNA.

Describe the structure and functional diversity of proteins.

Describe the synthesis of the biomacromolecules: polysaccharides, nucleic acids and proteins.

Water – what do you already know? Each water molecule consists of a single oxygen

atom covalently bonded to two hydrogen atoms. The main component of organisms. It provides the environment needed for metabolic

reactions to take place. A dipolar molecule – one side is positively charged

and the other is negatively charged. Water molecules are attracted to each other and

form hydrogen bonds easily (but these also break easily).

This allows it to have a low viscosity and act as a solvent.

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Carbohydrates All carbohydrates contain the elements

carbon, hydrogen and oxygen in varying ratios. The basic unit of a carbohydrate is a sugar

molecule – a monosaccharide. Glucose and fructose are examples. They have the formula C6H12O6.

A disaccharide contains two monosaccharides. E.g. sucrose and lactose. They have the formula C12H22O11.

A polysaccharide is a complex carbohydrate and contains many sugar units. E.g. starch, cellulose, glycogen.

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Lipids Fats, oils and waxes. Hydrophobic – no attraction to water; they are

insoluble. Contain C, H and O, but little water. Contain a lot more energy than any other

compound found in plants and animals. Fats are made of fatty acids and glycerol. A common fat is a tryglyceride – a single

glycerol with three fatty acids attached.NOW TEST

EACH OTHER!

Fatty Acid Tails are HYDROPHOBIC

Phospholipids Phospholipids are

made from glycerol, two fatty acids, and (in place of the third fatty acid) a phosphate group.

Phosphate ‘Head’ is HYDROPHILLIC

Phospholipids

Phospholipids will spread out on water into a single layer (monolayer) because of their hydrophilic heads and hydrophobic ends.

Hydrophobic tails (lipid)

Hydrophilic heads (phosphate)

Water

In the bilayer of the membrane, the non-polar tails face inwards and the polar heads face outwards.

Nucleic Acids DNA and RNA are examples of molecules in

the group called nucleic acids. DNA is a polymer of nucleotides. Each nucleotide is made of a sugar

(deoxyribose), a phosphate and a nitrogenous base.

A pentose (5 carbon)

sugar called

deoxyribose

A phosphate

group

An organic nitrogenous base, either

Thymine, Adenine,

Guanine or Cytosine

Nucleotides

DNA is an example of a group of molecules called nucleic acids.

It is made of monomers called mononucleotides.

A NUCLEOTIDE

Structure of DNA

The sugar and the phosphate join to form ‘a sugar phosphate backbone’.

The bases are complementary to each other and are held together by hydrogen bonds.

A polynucleotide chain is formed.

RNA: Ribonucleic acid Also a polymer of nucleotides. Exists as a single chain (rather than double like

DNA). The sugar is ribose instead of deoxyribose in DNA. The bases are Adenine, Guanine, Cytosine and

Uracil (instead of Thymine in DNA). There are three kinds of RNA, all of which have very

specific jobs: Messenger RNA (mRNA) – involved in protein synthesis. Transfer RNA (tRNA) – also involved in protein synthesis. Ribosomal RNA (rRNA) – part of the ribosomes.

Now complete Page 14 “Organic

Molecules” in your Student Workbook.

Proteins Use the plasticine to

make what you think a protein molecule might

look like.

What are Proteins? Proteins are organic molecules made of carbon,

hydrogen, oxygen and nitrogen. They sometimes also contain sulphur and may form complexes with other molecules.

Proteins are made of small units called amino acids. These link together by peptide bonds to form chains of polypeptides.

Musical Proteins

Types of Proteins

Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body.

Enzymes carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA.

Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs.

Structural proteins provide structure and support for cells. On a larger scale, they also allow the body to move.

Transport proteins bind and carry atoms and small molecules within cells and throughout the body.

Amino Acid Structure There are twenty different amino acids, but

they all have the general formula NH2.RCH.COOH

They all have an amino group

(basic)

They all have a

carboxyl group

(acidic)

The ‘R’ group differs between amino acids. It is always bonded to a C-H

Identify the amino, carboxyl and ‘R’ groups on the following amino acids:

Peptide Bonds: How do amino acids join together?

animation

Try and draw out 2

amino acids

linked by a peptide bond.

This reaction produces water? What type of reaction is it?

Two amino acids link together to

form a dipeptide. When more

amino acids are linked together, a polypeptide is

formed

Condensation Reaction At least two amino acids join together (with a

peptide bond) to form a larger _____________. A peptide bond forms between the _________

and __________ _____(hydroxyl) groups. _______ is released.

polypeptide

hydrogencarboxylic acid

Water

Hydrolysis Reaction Breaks the ________bond holding the amino

acids together. _______ is used to split the bond.

peptide

Water

Try and draw the basic structure of an amino acid (from memory!) labelling the different groups.

Amino Acid Structure

They all have an amino group

(basic)

They all have a

carboxyl group

(acidic)

The ‘R’ group differs between amino acids. It is always bonded to a C-H

Protein Structure

Find out:

a) what the primary, secondary, tertiary and quaternary structures of proteins are.

b) For each of the above, what type of bonding is involved in creating and maintaining the structures.

LEVEL OF STRUCTURE DESCRIPTION BONDING

INVOLVED

PrimarySpecific sequence of

amino acids forming a polypeptide chain

Peptide bonding

Secondary

Shape the polypeptide folds

into; an alpha helix or beta pleated sheet

(non-specific)

Hydrogen bonding

Tertiary

Caused by interactions between R groups which leads

to bending and twisting of the

polypeptide helix into a compact shape

Disulphide (between sulphurs on R groups)Hydrogen and ionic

bondsHydrophillic and

hydrophobic interactions

Quaternary

Combinations of a number of different polypeptide chains

and associated non-protein groups

As above

Structures

Primary structure – the long chain of _______ ______.

Secondary structure – a c____ and t______ chain of amino acids.

Tertiary structure – when the protein is _______ up tightly. The 3D shape of the tertiary structure is held together by _________ ______and intermolecular forces.

The 3D shape is important in situations like active sites in enzymes and use in cell membranes.

aminoacids

oiled wisted

folded

chemical bonds

SECONDARY STRUCTURE

Alpha Helix

An alpha helix is formed when hydrogen bonds form between the amino and carboxylic acid groups all along the chain.

This makes the chain coil up (like a DNA helix).

Beta-pleated Sheets

Parallel folded sections.

They are held in place by hydrogen bonds between the amino and carboxylic acid groups along the parallel chains.

TERTIARY STRUCTURE

Quaternary Structure

A protein that is made up of more than one folded protein unit joined together have quaternary structure.

____________ is an example – it has four joined polypeptide chains.

Haemoglobin

QUATERNARY STRUCTURE

The 3D shape depends on the primary structure because the amino acid side groups respond differently to water, altering the shape.

Hydrophobic – water repelling. A hydrophobic side group will turn inwards, away from the water, towards the centre of the protein molecule.

Hydrophilic – water attracting. A hydrophilic side group will turn outwards, forming hydrogen bonds with the surrounding water molecules.

KEY WORDS Anagrams1. ROTINPE2. RAYMIRP3. NODYCRASE4. RABCOXLYIC5. LAAPH LEIXH6. TITYREAR7. TEBA-DEELPAT8. GOBLINMEAOH9. NETRAQUYAR10.DITYEEPPOLP11.NOGHYEDR NOBD12.SORDYYISHL13.NOOTDENCANSI14.TIEDEPP NOBD15.NIMAO CAID

1. Protein2. Primary3. Secondary4. Carboxylic5. Alpha helix6. Tertiary7. Beta-pleated8. Haemoglobin9. Quaternary10.Polypeptide11.Hydrogen bond12.Hydrolysis13.Condensation14.Peptide bond15.Amino acid

Card sort Now complete the Proteins Key Terms card

sort

Proteins

1. Amino acids join together so that the hydrogen and hydroxyl groups meet. Water is removed in this reaction.

Carboxylic acid group

2. The amino acid group consisting of 2 hydrogen atoms and a nitrogen atom.

Amino group3. This type of bond is formed between the two amino acids.

Ions4. Polymers made up of long chains of 20 different amino acids.

R group5. The amino acid group consisting of COOH.

Condensation

6. This amino acid group varies from a single hydrogen atom, to a side chain several carbon atoms long, or containing a benzene ring.

Peptide bond7. Amino acids are soluble in water so they form these.

Proteins4. Polymers made up of long chains of 20 different amino acids.

Carboxylic acid group

5. The amino acid group consisting of COOH.

Amino group2. The amino acid group consisting of 2 hydrogen atoms and a nitrogen atom.

Ions7. Amino acids are soluble in water so they form these.

R group

6. This amino acid group varies from a single hydrogen atom, to a side chain several carbon atoms long, or containing a benzene ring.

Condensation

1. Amino acids join together so that the hydrogen and hydroxyl groups meet. Water is removed in this reaction.

Peptide bond3. This type of bond is formed between the two amino acids.

Dipeptide1. This structure is formed when the protein folds up tightly.

Hydrolysis

2. This structure is formed when proteins are made up of more than one folded protein unit joined together. E.g. haemoglobin.

Primary structure3. This reaction involves water being used to split the bond between amino acids.

Secondary structure

4. The name of the product formed between two amino acids.

Tertiary structure5. This structure is a long chain of amino acids.

Quaternary structure

6. This structure is formed from interactions between the different side groups of the amino acids, causing the long chain to coil and twist.

Dipeptide4. The name of the product formed between two amino acids.

Hydrolysis3. This reaction involves water being used to split the bond between amino acids.

Primary structure5. This structure is a long chain of amino acids.

Secondary structure

6. This structure is formed from interactions between the different side groups of the amino acids, causing the long chain to coil and twist.

Tertiary structure1. This structure is formed when the protein folds up tightly.

Quaternary structure

2. This structure is formed when proteins are made up of more than one folded protein unit joined together. E.g. haemoglobin.