Monomers and polymers, Carbohydrates and Lipids

describe the chemical reactions involved in converting monomers into polymers (2)

a condensation reaction joins monomers together and forms a chemical bond and releases water

describe the chemical reactions involved in converting polymers to monomers (2)

a hydrolysis reaction occurs to break the chemical bond between monomers and uses water

what is a monomer (1)

a smaller unit from which larger polymers are made

describe a biolchemical test to show that there is non-reducing sugars in a sample (3)

• heat the sample with acid and neutralise

• heat again with benedicts solution

• red percipitate for positive test

why would the use of a colorimeter improve the repeatibility of a student’s results (1)

standardises the method

how do you calculate total percentage error (1)

(percentage error A / vol of A) + (percentage error of B / vol of B ) x 100

describe the differences between the structure of a cellulose molecule and a glycogen molecule (4)

• cellulose only contains 1-4 glycosidic bonds whereas glycogen contains both 1-4 and 1-6 glycosidic bonds

• cellulose is made up of beta glucose whereas glycogen is made up of alpha glucose

• cellulose molecule has a straight chain whereas glycogen is branched

• cellulose molecule has a straight chain whereas glycogen is coiled

describe and explain features of starch that make it a good storage molecule (4)

• insoluble in water so it does not affect the water potential

• coiled therefore the molecule is compact and many can fit in a small area

• branched so has fast breakdown and enzyme action

• large molecule so it cant cross the cell membrane

what test is used to show the presence of starch (1)

iodine test

common monomers of glucose and what they are made of (3)

• maltose - glucose + glucose

• lactose - glucose + galctose

• sucrose - glucose + fructose

what type of bond joins together the glucose monomers (1)

glycosidic bond

explain how cellulose molecules structures are adapted for their function in plant cells (3)

• have long and straight chains

• these chains become linked together by many hydrogen bonds to form fibrils

• that provide strength in the cell wall

what is the general structure of a fatty acid (1)

RCOOH

what is the group represented by COOH in a fatty acid called (1)

carboxyl group

describe the test for the presence of a lipid in a sample (2)

• add ethanol and then add water and mix

• a milky emulsion shows a positive result

describe how a trigylceride is formed (3)

• 1 glycerol and 3 fatty acids

• condensation reaction occurs and removed 3 molecules of water

• an ester bond is formed

describe how an ester bond is formed in a phospholipid molecule (2)

• condensation reaction removes a water molecule

• between glycerol and fatty acid

what bond is formed in a triglyceride (1)

an ester bond

describe how you would test a piece of food for the presence of a lipid (2)

• dissolve in alcohol and then water

• milky emulsion shows a positive result

name 3 polysaccharides (3)

• starch

• glycogen

• cellulose

what are the roles of lipids (3)

• insulation

• waterproofing

• source of energy when oxidised

what is an alpha helix structure (1)

hydrogen bonds form every 4th peptide bond

what is a beta pleated sheet structure (1)

protein folds so two parts of polypeptide chain are parallel to each other enabling hydrogen bonds to form

what is a globular protein (1)

compact, roughly spherical protein which is soluble in water

what is a fibrous protein (1)

long strands of polypeptide chains with cross-linkages due to hydrogen bonds which is insoluble in water

what is the molecular structure of hemoglobin (7)

• 4 polypeptide chain

• globular protein therefore soluble in water

• hydrophilic R-groups face outwards

• maintains its 3D spherical shape

• hydrophobic R-groups face inwards

• maintains its solubility

• each subunit has a haem group which contains ironII

what is the function of hemoglobin (1)

binds to oxygen in the lung

what is the molecular structure of collagen (5)

• insoluble fibrous protein

• has 3 polypeptide chains

• these chains are held by hydrogen bonds

• helix shape

• in its primary structure, almost every 3rd amino acid is glycine

compare the structure of hemoglobin and collagen (6)

• collagen has 3 polypeptide chains whereas haemoglobin has 4

• collagen is long and thin whereas haemoglobin is spherical

• collagen is fibrous whereas haemoglobin is globular

• collagens amino acid chain is repetitive whereas haemoglobins is variable

• haemoglobin has a haem group and collagen does not

• collagen is insoluble in water whereas haemoglobin is soluble

compare the properties of a phospholipid and triglyceride (4)

• triglyceride consists of a glycerol molecule and 3 fatty acids whereas a phospholipid contains 2 fatty acids, one glycerol molecule, and a phosphate group

• phospholipids are amphipathic whereas triglycerides are non-polar

• phospholipids have a structural role in cell membranes whereas triglycerides provide long-term energy storage and insulation

• phospholipids are soluble in water whereas triglycerides are insoluble in water

Give polymer examples of the monomer glucose (3)

Starch

Cellulose

Glycogen

What is a condensation reaction (3)

Joins two molecules

Creating a chemical bond

By removing a water molecule

Define hydrolysis (3)

Break chemical bond

Between 2 molecules

Using a water molecule

What bond joined two monosaccharides (1)

Glycosidic bond

What is the function of starch (2)

Store of glucose

In plants

What is the function of cellulose (2)

Structural strength

In cell wall of plants

What is the function of glycogen (2)

Store of glucose

In animals

Explain the structure of starch (5)

1-4 glycolic bonds in amylose and 1-4 and 1-6 bonds in amylopectin

Made of 2 polymers: amylose and amylopectin

Helix compact to fit a lot of glucose in small space

Branched structure increases surface area for rapid hydrolysis back to glucose

Insoluble therefore does not affect water potential

Explain the structure of cellulose (5)

1-4 glycosidic bonds

Polymer forms long straight chains

Chains are held in parallel by many hydrogen bonds to form fibrils

Many hydrogen bonds provide collective strength

Insoluble therefore does not affect water potential

Explain the structure of glycogen (3)

1-4 and 1-6 glycosidic bonds

Highly branched molecule therefore increased surface area for hydrolysis back to starch

Insoluble therefore does not affect water potential

How do the triglyceride structure result in it’s properties (4)

Energy storage due to large ratio of carbon-hydrogen bonds

High ratio of hydrogen to oxygen atoms therefore act as a metabolic water source by releasing water when oxidised

Triglycerides do hint affect the water potentials and osmosis as they are hydrophobic

Have low mass therefore a lot can be stored without increasing mass a lot

Describe how a peptide bond is formed between 2 amino acids to form a dipeptide (2)

1. Condensation reaction between NH2 groups and COOH group

2. Forming peptide bond

Explain secondary structure of proteins (3)

1. Hydrogen bonds between peptides forming polypeptides

2. Between NH and C=O

3. Forming beta pleated sheet

Explain how 2 proteins can have same number and type of amino acids but different tertiary structures (2)

1. Different sequence of amino acids

2. Different bonds form hydrogen / ionic / disulphide bridges

Why is increased cholesterol better for red blood cells (3)

1. Increases stability of cells

2. By making membranes less flexible

3. As red blood cells are not supported by other cells so they need the stability

Explain how cells can maintain constant shape despite having no cholesterol (2)

1. Has cell wall

2. Which is rigid due to murein

Explain how cellulose molecules are adapted for their function in plant cells (3)

1. Long straight chains

2. Become linked via many hydrogen bonds

3. Providing strength to cell wall

Describe how proteins are digested in human gut (5)

1. Peptide bonds between amino acids are broken

2. Via hydrolysis

3. Endopeptidase hydrolyses polypeptides in peptides

4. Exopeptidases hydrolyses terminal amino acids on peptides

5. Dipeptidase hydrolyses dipeptides into amino acids

What sugars would you expect to be produced during chewing (2)

1. Maltose

2. As salivary amylose breaks down starch