Biological Molecules - Carbohydrates, Lipids and Proteins

Question 2

Define a monosaccharide

Answer 2

The monomer of a carbohydrate

Question 3

Name 3 monosaccharides

Answer 3

Glucose

Fructose

Galactose

Question 4

What is the structural difference between alpha and beta glucose?

Answer 4

The hydroxyl and hydrogen groups on the right of the molecules are flipped

Question 5

Define a disaccharide

Answer 5

A disaccharide consists of 2 monosaccharides bonded with a glycosidic bond

Question 6

Name 3 examples of disaccharides

Answer 6

Maltose

Sucrose

Lactose

Question 7

What are the monosaccharides of maltose?

Answer 7

2 alpha glucose

Question 8

What are the monosaccharides of sucrose?

Answer 8

Glucose and fructose

Question 9

What are the monosaccharides of lactose?

Answer 9

Glucose and galactose

Question 10

What is a structural polysaccharide found in animals?

Answer 10

Chitin

Question 11

What are 3 examples of polysaccharides?

Answer 11

Cellulose

Glycogen

Starch

Question 12

What are the monosaccharides of cellulose?

Answer 12

Chains of beta glucose

Question 13

What are the monosaccharides of glycogen

Answer 13

Chains of alpha glucose

Question 14

What are the monosaccharides of starch?

Answer 14

Chains of alpha glucose

Question 15

What are 3 examples of hexoses?

Answer 15

Glucose

Fructose

Galactose

Question 16

Define a condensation reaction

Answer 16

The process where 2 monomers form a covalent bond and a H20 molecule is lost

Question 17

Define hydrolysis

Answer 17

The process where water is added to a polymer under certain conditions, breaking the covalent bond and releasing the individual monomers

Question 18

Describe the Benedict’s test for sugars

Answer 18

• add an excess of Benedict’s reagent (blue)
• Heat in a boiled water bath
• If the test is positive, a coloured precipitate will form
• Green (very low), Yellow (low), Orange (medium), Red (high)

Question 19

What is the structure of glycogen and where is it found?

Answer 19

Glycogen consists of multi-branched, short chains of alpha glucose

It is found in animals (liver and muscles) and plants

Insoluble and large

Question 20

What is the function of glycogen?

Answer 20

Storage molecule

Synthesized from alpha glucose when blood sugar levels are too high

Can be easily broken down into an energy source when blood sugar levels are too low

Question 21

How does the structure of glycogen help its function?

Answer 21

Glycosidic bonds are easily broken by water

Multiple branches provide quick breakdown

Low osmotic potential means it doesn’t diffuse in and out of cells and also doesn’t affect the volume of water of cells

Question 22

What is structure of starch?

Answer 22

Starch consists of alpha glucose chains and specific to plants only

The 2 types are amylose (unbranched) and amylopectin (branched)

Forms close spirals and is insoluble

Question 23

What is the function of starch?

Answer 23

It is designed for use in respiration and long term storage in plants

Used when there is limited light -> less photosynthesis

Stored in seeds in order for them to grow before they can photosynthesise

Question 24

How does the structure of starch help its function?

Answer 24

The long chains wind up tightly

• efficient storage
• Monomers can be hydrolyzed for energy use
• Amylopectin used for shorter term energy release as it is branched
• Amylose used for longer term energy release as it is unbranched

Question 25

What is the structure of cellulose?

Answer 25

Chains of beta glucose, resulting in every other molecule being flipped Flipped molecules can form hydrogen bonds with the parallel chain below, forming a strong, rigid polymer

Question 26

What is the function of cellulose?

Answer 26

To provide structure - it makes up 30% of the cell wall in plants

Question 27

How does the structure of cellulose help its function?

Answer 27

The beta glucose linkages gives it a flat a rigid structure which helps it to provide structure throughout different organisms

Question 28

What are the properties of lipids?

Answer 28

Double energy:mass ratio than carbohydrates Insoluble in water but soluble in organic substances High ratio of H:O so releases water when oxidised

Question 29

What are the functions of lipids?

Answer 29

Energy storage molecules Waterproofing Insulation Physical protection

Question 30

What are the major differences between fats and oils?

Answer 30

Fats: Solid at 10 - 20 degrees, saturated Oils: Liquid at room temp , unsaturated

Question 31

What are the 3 types of triglyceride tails?

Answer 31

- Saturated -\> no double bonds - Unsaturated -\> one double bond - Polyunsaturated -\> multiple double bonds

Question 32

What is the structure of a triglyceride?

Answer 32

3 fatty acid tails combined with a glycerol head by an ester bond

Question 33

Define a phospholipid?

Answer 33

Similar to lipids except one fatty acid is replaced with a phosphate molecule

Question 34

What is the relationship between phospholipids and water?

Answer 34

Phospholipids have a hydrophilic head and a hydrophobic tail This causes them to form structures such as lipid bilayers in water

Question 35

What are amino acids composed of?

Answer 35

Centre alpha C Solitary H branch Amino group Carboxyl group R (variable) group

Question 36

How many amino acid variations are there?

Answer 36

20

Question 37

What feature of amino acids provides indirect evidence for evolution?

Answer 37

The same 20 amino acids occur in all living organisms

Question 38

How many structural levels occur in proteins?

Answer 38

Proteins can have up to 4 levels of structure Some only need 3 -\> only the large proteins have quaternary structure

Question 39

What is the primary structure of proteins?

Answer 39

The synthesis of amino acids into a polypeptide chain

Question 40

What is the secondary structure of proteins?

Answer 40

This occurs as H bonds form between the H+ ions and O- ions of the carboxyl group These bonds are relatively weak but contain enough strength to fold the polypeptide chain into a 3D shape

Question 41

What are 2 examples of shapes formed in secondary structure?

Answer 41

Alpha helix Beta pleated sheet

Question 42

What is the tertiary structure of proteins?

Answer 42

Result of further twisting of the secondary structure Can be complex and is specific to the protein Plays a significant role in determining the behaviours of the protein Maintained by 3 types of bonds

Question 43

What are the 3 types of bond that maintain tertiary structure?

Answer 43

Disulfide bonds - strong and not easily broken Ionic bonds - formed between the carboxyl and amino groups that weren't involved in peptide bonds, weaker than disulfide bonds and easily broken by pH changes Hydrogen bonds - numerous but easily broken

Question 44

What is the quaternary structure of proteins?

Answer 44

Multiple polypeptides bond together eg Haemoglobin

Question 45

If 2 proteins have the same and type of amino acids, why will they have different tertiary structures?

Answer 45

The amino acids are in different orders This means that different hydrogen, ionic and disulfide bonds will form, twisting the polypeptide into a different shape

Question 46

What is the test for lipids?

Answer 46

The Emulsion Test Add ethanol to the sample in a 5:2 ratio of ethanol:sample If lipids are present, a white emulsion will form

Question 47

What are the types of proteins?

Answer 47

Fibrous proteins eg collagen Globular proteins eg enzymes

Question 48

What is the function of a fibrous protein?

Answer 48

Fibrous proteins have structural functions eg collagen is found in tendons (joining muscles to bones)

Question 49

What is the function of a globular protein?

Answer 49

Globular proteins perform metabolic functions eg enzymes catalyse digestion

Question 50

How are the structures of fibrous and globular proteins different?

Answer 50

Fibrous proteins have a quaternary structure with 2 other polypeptide chains Globular proteins only have a tertiary structure, not quaternary

Question 51

Describe the structure of collagen and how it is formed

Answer 51

Primary Structure -\> coiled chain Secondary Structure -\> tightly coiled into an alpha helix Tertiary Structure -\> also an alpha helix Quaternary Structure -\> 3 double coiled polypeptide chains wound together

Question 52

What is the tertiary structure of haemoglobin?

Answer 52

2 alpha helices and 2 beta pleated sheets