Topic 1 Biological molecules

What is a monomer?

Monomers are the smaller units from which larger molecules are made.

What is a polymer?

Polymers are molecules made from a large number of monomers joined together.

what are the polymers of glucose?

starch, glycogen, cellulose

what is the polymer of amino acid?

protein

what are the polymers of nucleotides?

DNA and RNA

Name 3 monosaccharides

glucose, fructose, galactose

Name 3 dissacharides.

sucrose, lactose, maltose

Name 3 polysaccharides

starch, glycogen, cellulose

How are dissacharides formed?

made of two monosaccharides

joined together by a glycosidic bond

formed via a condensation reaction

How is maltose formed?

maltose is a disaccharide formed by condensation of two glucose molecules

How is sucrose formed?

sucrose is a disaccharide formed by condensation of a glucose molecule and a fructose molecule

How is lactose formed?

lactose is a disaccharide formed by condensation of a glucose molecule and a galactose molecule.

What is a condensation reaction?

A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

What is hydrolysis?

A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.

How are polysaccharides formed?

Polysaccharides are formed by the condensation of many glucose units.

how are glycogen and starch formed?

Glycogen and starch are formed by the condensation of α-glucose.

How is cellulose formed?

Cellulose is formed by the condensation of β-glucose.

describe the structure and function of glycogen?

• animals cells get energy from glucose too, but animals, store excess glucose as glycogen.

Its structure has loads of side branches. This means that stored glucose can be released quickly, which is important for energy release in animals.

It's also very compact.

describe the structure and function of starch?

Cells get energy from glucose. Plants store excess glucose as starch. When it needs more glucose, it breaks down starch to release the glucose.

Amylose: long, unbranched chain of alpha-glucose arranged in a coiled structure. This makes the molecule compact, so it's really good for the storage of energy

describe the structure and function of starch?

Amylopectin: highly branched molecule that allows for the fast release of energy, as there are many points available for enzymes to act on

-Starch is insoluble, too large to leave the cell and good for storage

describe the structure and function of cellulose?

1} Cellulose is made of long, unbranched chains of beta glucose.

2) When beta-glucose molecules bond, they form straight cellulose chains.

describe the structure and function of cellulose?

3) The cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils. The strong fibres mean cellulose provides structural support for cells (e.g. in plant cell walls).

Name and outline the test for reducing sugars

• Add Benedict's reagent (which is blue) to a sample, and heat it in a water bath that's been brought to the boil

• If the tests positive it will form a coloured precipitate

• it should change from blue to green, yellow, orange and red

• Reducing sugar a include all monocharides and some disaccharides (maltose and lactose)

Outline the test for non- reducing sugars

• break it down into monosaccharides

• to do this you get a new sample of the test solution, add dilute hydrochloride acid and heat it it in a water batht that's been brough to the boil.

You then neutralise it with sodium hydrogen carbonate.

The carry out the Benedict's test. It the test positive it will form a coloured precipitate. If negative the solution will stay blue, so it doesn't contain any sugar.

Outline the test for starch

A chemical test for starch is to add iodine solution to food (yellow/brown) and look for a colour change. In the presence of starch, iodine turns a blue/black colour

How are triglycerides formed?

Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid.

A condensation reaction between glycerol and a fatty acid (RCOOH) forms an ester bond.

What is a saturated fatty acid?

The hydrocarbon chain has only single bonds between carbons

What is a unsaturated fatty acid?

the hydrocarbon chain has at least one double bond between carbons.

describe the properties of triglycerides?

•High ratio of energy storing carbon-hydrogen bonds to carbon atoms and therefore they are an excellent energy store.

• A low mass to energy ratio meaning that they are a good storage molecule, with a lot of energy being stored in a small volume. This is beneficial for animals as it is less mass to move around.

• Being large and non-polar lipids are insoluble in water and therefore their storage does not affect the water potential of cells.

• A high ratio of hydrogen-oxygen atoms means that triglycerides release water when they are oxidised and therefore provide and important source of water for organisms to live in dry environments.

Describe the emulsion test.

The procedure is for the sample (food) to be suspended in ethanol, allowing lipids present to dissolve (lipids are soluble in alcohols). The liquid (alcohol with dissolved fat) is then decanted into water.

What is a phospholipid?

In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group.

describe the properties of phospholipids?

Phosphate heads are hydrophilic (loves water) and the tails are hydrophobic (hates water)

hydrophilic head can attract water as its charged

due to the phosphate being charged it repels other fats

the fatty acid chain is not charged, its known as the hydrophobic tail and it repels water but will mix with fats.

2 charged regions so they are polar

• In an aqueous environment being polar means a bilayer can be formed which make up the plasma membrane around the cells

What are proteins?

• The monomers of proteins are amino acids

• A dipeptide is formed when two amino acids join together

• A polypeptide is formed when more than two amino acids join together

• Proteins are made up of one or more polypeptides

describe how amino acids are joined together to form a dipeptide?

Dipeptides are formed by the condensation of two amino acids. peptide bond forms between OH of carboxyl group and H of amine group.

Describe the primary structure of a protein

order and number of amino acids in a protein.

Describe the secondary structure of a protein

The polypeptide the amino acids in the chain. This makes it automatically coil into an alpha (a) helix or fold into a (b) pleaded sheet.

Describe the tertiary structure of a protein

Tertiary structure

• is when the coiled or folded chain of amino acids is often coiled and folded further. More binds form between different parts of the polypeptide chain, including hydrogen bonds and ionic bonds (attractions between negative and positive charges on different parts of the molecule)

Disulfide bridges also form whenever two molecules of the amino acid cysteine come closer- the sulcus atom in one cysteine bonds to the soulful atom in the other. For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

Describe the quaternary structure of a protein

Some proteins are made of several polypeptide chains held together by bonds. The quaternary structure is The way these polypeptide chains are assembled together. For proteins made from more than one polypeptide (haemoglobin, insulin, collagen), the quaternary structure is the proteins final 3D structure.

functions of proteins

1. Structural Support:

Proteins form the structural framework of cells and tissues, providing shape and support.

Examples include collagen in skin and tendons, and keratin in hair and nails.

functions of proteins

5. Antibodies:

Antibodies are proteins that recognize and neutralize foreign invaders, like bacteria and viruses, as part of the immune system.

Functions of proteins

Transport:

Proteins transport substances across cell membranes and throughout the body.

Examples include hemoglobin, which carries oxygen in the blood, and ferritin, which transports and stores iron.

Functions of proteins

Proteins called enzymes act as biological catalysts, speeding up chemical reactions within the body.

They are essential for digestion, breaking down food into smaller molecules that can be absorbed.

Enzymes are involved in a wide range of metabolic processes.

what is the test for proteins

The Biuret test

1. Place the sample to be tested in a test tube and add an equal volume of sodium hydroxide at room temperature.

2. Add a few drops of very dilute (0.05%) copper (II) sulfate soliton and mix gently.

what is the test for proteins

3. A purple colouration indicates the presence of a peptide bond and hence a protein. A negative result would mean the solution remains blue.

What are enzymes and describe the specificity and properties relating to the tertiary structure.

1) Enzymes catalyse metabolic reactions-

2) they can affect structures in an organism (e.g. enzymes are involved in the production of collagen, an important protein in the connective tissues of animals) as well as functions of animals (like respirations)

3) they can be intracellular- within cells or extracelluar (outside cells)

What are enzymes and describe the specificity and properties relating to the tertiary structure.

4) they are proteins

5) they have an active site, which has an specific shape. The active site is the part of the enzyme where the substrate molecules (the substance that the enzyme interacts with) binds to.

6) enzymes are highly specific due to their tertiary structure

How do enzymes speed up chemical reactions?

Enzymes increase rate of reaction by lowering the activation energy of the reaction they catalyse.

Describe the lock and key model

1. Substrate collides with the active site of an enzyme

2. Substrate binds, enzyme-substrate complex forms

3. Substrate converted to products

4. Products released from the active site which is now free to bind to another substrate

Describe the induced fit model of enzyme action

Active site / enzyme not complementary;

Active site changes (shape) / is flexible;

(Change in enzyme allows) substrate to fit / E-S complex to form;

what factors affect the rate of enzyme controlled reactions?

Temperature

ph

substrate and enzyme concentration

inhibitors

what is the effect of temperature on enzymes?

1) The rise in temperature makes the enzyme's molecules vibrate more.