Biological Molecules

Question 1

State the functions of water

Answer 1

• Reactant
• Solvent
• Transports substances
• Temperature control (high specific heat capacity and high latent heat of vaporisation)
• Habitat (becomes less dense when frozen so organisms can survive and reproduce

Question 2

Water is a polar molecule. What does this mean?

Answer 2

It has a partial negative charge on one side due to unshared negative electrons on the oxygen atoms. It has a partial positive charge on the other side due to hydrogen.

Question 3

What bonding occurs between hydrogen and oxygen? What does this mean?

Answer 3

Hydrogen bonding
Lots of energy is required to break hydrogen bonds
Water is a liquid at room temperature

Question 4

Water is an important metabolite. What does this mean?

Answer 4

It can be used in condensation and hydrolysis reactions

Question 5

Why is it important for ice to be less dense than liquid water?

Answer 5

Living organisms beneath the ice do not freeze and can survive because ice forms a insulating layer

Question 6

Why is water a good solvent?

Answer 6

Water is a polar molecule so it separates an ion based on its charge. E.g O- will be attracted to Na+

Question 7

What is a polymer?

Answer 7

Large, complex molecules composed of long chains of monomers

Question 8

How do you make a polymer?

Answer 8

A condensation reaction forms a chemical bond between monomers, releasing a molecule of water

Question 9

How do you break down a polymer?

Answer 9

A hydrolysis reaction breaks the chemical bond between monomers using a water molecule

Question 10

What is a monosaccharide? What are some examples?

Answer 10

A monomer for a carbohydrate
(CH2O)n
Glucose, galactose, fructose
All C6H12O6

Question 11

What is the difference between alpha glucose and beta glucose?

Answer 11

There is a change in spacial arrangement of atoms
The OH and H groups are flipped at C1

Question 12

What is the difference between beta glucose and galactose?

Answer 12

The arrangement of the OH group and the H group are flipped at C4

Question 13

What is a disaccharide and how do they form?

Answer 13

Two monosaccharides joined by a condensation reaction at their OH groups

Question 14

What is the disaccharide created when two alpha glucoses join together?

Answer 14

Maltose

Question 15

What bond forms between two monosaccharides?

Answer 15

A glycosidic bond

Question 16

What is sucrose made from?

Answer 16

Glucose and fructose

Question 17

What is lactose made from?

Answer 17

Glucose and galactose

Question 18

What is a polysaccharide?

Answer 18

A long chain of monosaccharides joined together by glycosidic bonding condensation reactions

Question 19

What is starch?

Answer 19

A long chain of alpha glucose that has been polymerised together. It has 1,4 glycosidic bonds. It can be coiled in a helix and is only found in plant cells

Question 20

What are some of the functions of starch?

Answer 20

Can be coiled = compact
Insoluble = good for storage
Branched = increased SA for enzymes to act on

Question 21

What molecules is starch made of?

Answer 21

Amylose and amylopectin

Question 22

Alpha glucose can polymerise to make glycogen. What makes it different to starch?

Answer 22

Shorter
More branched
1,4 and 1,6 glycosidic bonds
Found in animal cells (liver and muscle)

Question 23

What are the functions of glycogen?

Answer 23

Very branched so it can be broken down into alpha glucose very quickly for respiration
Insoluble = no effect on osmosis

Question 24

What is cellulose?

Answer 24

Beta glucose can polymerise into cellulose
Straight, unbranched chains that run parallel to eachother crosslinked by hydrogen bonds

Question 25

What is the function of cellulose?

Answer 25

Structural Found in plant cell walls

Question 26

How do you test for monosaccharides and some disaccharides?

Answer 26

Benedict’s test for reducing sugars 2cm3 of sugar solution in test tube and 2cm3 of Benedict’s solution, heat for 5 mins Brick red is a positive result

Question 27

What needs to be done non reducing sugars (disaccharides) before the Benedict’s test?

Answer 27

Break glycosidic bond and turn them back into monomer using dilute hydrochloric acid, heat and sodium hydrogen carbonate

Question 28

How do you carry out a quantitative test for a reducing sugar?

Answer 28

- weight precipitate formed and compare samples - use colorimeter to quantity colour change

Question 29

What is the test for starch? What is a positive result?

Answer 29

Iodine test using iodine drops Positive test would be blue black

Question 30

Lipids are insoluble in water. What are they soluble in?

Answer 30

Organic solvents (alcohol)

Question 31

What are examples of lipids?

Answer 31

Triglycerides (fats and oils) Phospholipids

Question 32

How much more energy will lipids release than carbohydrates?

Answer 32

Twice as much

Question 33

State some functions of lipids

Answer 33

- lipid cuticles conserve water in plants - oily glands in skin - insulation (fat is a poor conductor of heat) - electrical insulation around nerve cells

Question 34

What is the test for lipids?

Answer 34

Mix test solution with ethanol Shake for 1 minute Add water Positive = cloudy solution

Question 35

What are triglycerides made of?

Answer 35

One glycerol attached to three fatty acids via ester bonds through a condensation reaction

Question 36

There are over 70 different fatty acids. What does this mean for triglycerides?

Answer 36

Wide variation

Question 37

What are unsaturated fatty acids?

Answer 37

The hydrocarbon tail has at least one double carbon-carbon bond causing the hydrocarbon tail to kink y A polyunsaturated fatty acid has many double bonds

Question 38

What are saturated fatty acids?

Answer 38

The hydrocarbon tail has single carbon-carbon bonds

Question 39

What are phospholipids made of?

Answer 39

A phosphate group joined to one glycerol and two fatty acids via ester bonds formed in a condensation reaction

Question 40

What part of a phospholipid is hydrophilic and what part is hydrophobic?

Answer 40

The head is hydrophilic The tail is hydrophobic

Question 41

What is a phospholipid bilayer?

Answer 41

Forms the cell membrane Hydrophobic middle of tails stops water soluble molecules from passing the membrane and into specialised proteins instead.

Question 42

What is the structure of cholesterol?

Answer 42

A hydroxyl group joined to hydrocarbon rings and a hydrocarbon tail

Question 43

What is the function of cholesterol?

Answer 43

Helps regulate the fluidity of the membrane by interacting with the phospholipid bilayer In hot temperatures, it makes the cell membrane less fluid and more rigid by binding to hydrophobic tails

Question 44

What are triglycerides mainly used for?

Answer 44

Energy storage molecules

Question 45

Draw the basic structure of an amino acid

Answer 45

R | H- N -C- C = O | | | H H O - H

Question 46

What is the R group in an amino acid?

Answer 46

The variable group that changes the structure and properties of an amino acid

Question 47

What is the H-N group called? | H

Answer 47

Amine group

Question 48

What is the C=O called? | O-H

Answer 48

Carboxyl group

Question 49

What is the bond formed between two amino acids called? How does it form? Where does it form?

Answer 49

Peptide bond Condensation reaction Between the C and N of amino acids

Question 50

What is the difference between a dipeptide and a polypeptide?

Answer 50

A polypeptide is lots of amino acids whereas a dipeptide is only two

Question 51

Polypeptide chains can fold up to make proteins. What are some examples of proteins?

Answer 51

Enzymes - break down large molecules Structural proteins - strong and stable long parallel peptide chains Antibodies - immune response Transport proteins - channel proteins

Question 52

How do you test for proteins?

Answer 52

Biuret test Equal volumes of test solutions and sodium hydroxide Add a few drops of dilute copper sulfate Positive = purple

Question 53

What is the primary structure of proteins?

Answer 53

The sequence (determined by the dna base sequence) of amino acids in a polypeptide chain Peptide bonds

Question 54

What is the secondary structure of proteins?

Answer 54

Polypeptide chain folded into an alpha helix or beta pleated sheet Peptide bonds and hydrogen bonds

Question 55

What is the tertiary structure of proteins?

Answer 55

Alpha helix or beta pleated sheet folds into the final 3D structure of a protein Peptide bonds Hydrogen bonds (weak alone) Disulfide bridges (very strong) Ionic bonding between the carboxylate and amine groups

Question 56

What is the quaternary structure of a protein?

Answer 56

Multiple polypeptide chains folded and assembled together

Question 57

What are fibrous proteins? Give examples.

Answer 57

Structural insoluble proteins Collagen (strong, bone, muscle, skin) keratin (waterproof, skin, nails) and elastin (stretchy, skin, ligaments)

Question 58

What are globular proteins? Give examples.

Answer 58

Soluble, round and compact Hydrophilic and hydrophobic interactions Enzymes, metabolic functions Haemoglobin, insulin (hydrophilic R groups) and pepsin (acidic R groups)

Question 59

Haemoglobin is a conjugated protein. What does this mean and what does it allow it to do?

Answer 59

Each 4 polypeptide chains have a prosthetic haem group containing iron allowing it to bind to oxygen

Question 60

What is an inorganic ion?

Answer 60

An atom that has a charge

Question 61

What is the Rf value equation?

Answer 61

Distance travelled by substance/distance travelled by solvent

Question 62

Chromatography separates a mixtures and components move at visual different rates. What are some of the uses for chromatography?

Answer 62

Identify amino acids or photosynthetic pigments in leaves Can test for drugs in urine of athletes Analyse purity of drugs Analyse food for contaminants