Biological molecules

Define monomer

Smaller, repeating units from which larger molecules/polymers are made.

Define Polymer

Molecules made from many identical/similar monomer molecules.

What 3 things happen in a condensation reaction?

1. 2 molecules join together

2. forming a chemical bond

3. releasing a water molecule

What 3 things happen in a hydrolysis reaction?

1. 2 molecules seperated

2. breaking a chemical bond

3. Using a water molecule

Nucleotide is a monomer. What is its polymer?

Polynucleotide (DNA or RNA)

What is the polymer of glucose?

starch

What is the polymer of amino acids?

proteins

What are monosaccharides?

monomers from which large carbohydrates are made.

Give 3 examples of monosaccharides

1. Glucose

2. fructose

3. galactose

Draw structure of a-glucose

OH on bottom of both sides

Describe the difference between the structure of a-glucose and B-glucose

Isomers - same molecular formula but differently arranged atoms

OH group is below carbon 1 in a-glucose but above carbon 1 in B-glucose

What are disaccharides and how are they formed?

2 monosaccharides joined together with a glycosidic bond.

Formed by a condensation reaction, releasing a water molecule

List 3 common disaccharides and monosaccharides from which they’re made.

a-glucose + a-glucose = maltose

glucose + galactose = lactose

fructose + glucose = sucrose

What are polysaccharides and how are they formed?

many monosaccharides joined together with glycosidic bonds

Formed by many condensation reactions, releasing many water molecules

What’s the basic function of starch?

Energy store in plant cells

What’s the basic function of glycogen?

Energy store in animal cells

State 3 points regarding the basic structure of starch

1. Polysaccharide of a-glucose

2. Some has 1,4-glycosidic bonds so is unbranched (amylose)

3. some has 1,4- and 1,6-glycosidic bonds so is branched (amylopectin)

State 2 points regarding the basic structure of glycogen

1. polysaccharide made of a-glucose

2. 1,4- and 1,6-glycosidic bonds = branched

Explain how the structure of starch (amylose) relates to its function.

Helical - compact for storage in cell

Large, insoluble polysaccharide molecule - can’t leave cell/cross cell membrane

Insoluble in water - water potential of cell not affected (no osmotic effect)

Explain how the structures of glycogen and starch amylopectin relate to their functions

branched = compact

branched = more ends for faster hydrolysis - release glucose for respiration to make ATP for energy release

Large, insoluble polysaccharide molecule - can’t leave cell/cross cell membrane

insoluble in water - water potential of cell not affected (no osmotic effect)

Describe the basic function of cellulose

Provides strength and structural support to plant/algal cell walls

Describe the basic structure of cellulose

Polysaccharide of B-glucose

1,4-glycosidic bonds so forms straight, unbranched chains

Chains linked in parallel by hydrogen bonds, forming microfibrils

Explain how the structure of cellulose relates to its function

Every other B-glucose molecule is inverted in a long, straight, unbranched chain.

Many hydrogen bonds link parallel strands to form microfibrils (strong fibres).

Hydrogen bonds are strong in high numbers

so provides strength to plant cell walls

Name 3 reducing sugars

monosaccharides, maltose and lactose

Describe the test for reducing sugars in 3 steps

1. Add Benedict’s solution (blue) to sample

2. Heat in a boiling water bath

3. Positive result = green/yellow/orange/brick red precipitate

Describe the test for non-reducing sugars in 5 steps

1. Do Benedict’s test and stays blue/negative

2. heat in a boiling water bath with acid (to hydrolyse into reducing sugars)

3. neutralise with alkali (e.g. sodium bicarbonate)

4. heat in a boiling water bath with benedict’s solution

5. positive result = green/yellow/orange/brick red precipitate

Name a non-reducing sugar

sucrose

Suggest a method to measure the quantity of sugar in a solution

Carry out Benedict’s test, then filter and dry precipitate

find mass/weight

Describe the biochemical test for starch

Add iodine dissolved in potassium iodide (orange/brown) and shake/stir

Positive result = blue-black

Name 2 groups of lipid

triglycerides and phospholipids