2.1.2 biological molecules

Question 1

describe amylose

Answer 1

• polymer of alpha glucose joined by 1-4 glycosidic bonds
• very compact
• not very soluble

Question 2

describe amylopectin

Answer 2

• polymer containing alpha glucose molecules formed by 1-4 glycosidic bonds with 1-6 glycosidic bond branches
• highly branched so can be broken down easily
• can be hydrolysed quicker than amylose

Question 3

where is starch stored?

Answer 3

intracellular starch grains known as plastids

Question 4

what are the 3 polysaccharides?

Answer 4

• starch
• cellulose
• glycogen

Question 5

describe cellulose

Answer 5

• polymer made of long chains of beta glucose molecules with 1-4 glycosidic bonds
• high tensile strength
• permeable to numerous substances (prevents cell bursting from excess water)
• inert/ unreactive

Question 6

what is different about the chains of beta glucose molecules?

Answer 6

the molecules are joined together with each alternating molecule inverted

Question 7

describe glycogen

Answer 7

• polymer consisting of many alpha 1-6 glycosidic bonds with even more branched structures
• stored as small granules in cell cytoplasm ( muscle + liver)
• less dense
  -more soluble
• hydrolysed very quickly (can be broken down rapidly)

Question 8

what are monosaccharides?

Answer 8

simple sugar molecules which link to form polymers and are all reducing sugars

Question 9

what is the difference between alpha and beta glucose

Answer 9

the -OH group in alpha glucose is below the first carbon atom
the -OH group in beta glucose is above the first carbon atom

Question 10

what are the 3 monosaccharides?

Answer 10

• glucose
• fructose
• galactose

Question 11

what is a disaccharide?

Answer 11

sugar molecules that are formed when monosaccharides join through condensation reactions with glycosidic bonds

Question 12

what are the 3 disaccharides?

Answer 12

• maltose
• lactose
• sucrose

Question 13

what is maltose formed from

Answer 13

• 2 alpha glucose molecules
• joined by alpha 1-4 glycosidic bond

Question 14

what is lactose formed from

Answer 14

• beta glucose and galactose
• joined by beta 1-4 glycosidic bond

Question 15

what is sucrose formed from

Answer 15

• alpha glucose and fructose
• joined by alpha 1-4 glycosidic bond

Question 16

what does the general structure of a protein include?

Answer 16

• carboxylic acid group
• amino group
• R group

Question 17

what reaction makes a protein and what type of bond forms?

Answer 17

• condensation reaction forms a peptide bond to make dipeptide molecules

Question 18

what are the 4 structures of proteins?

Answer 18

• primary structure
• secondary structure
• tertiary structure
• quaternary structure

Question 19

describe the primary structure of a protein

Answer 19

• order of amino acids that make up one polypeptide chain

Question 20

describe the secondary structure of a protein

Answer 20

• the folding of the protein which is held together by hydrogen bonds between -CO and -NH

Question 21

what are the 2 forms of secondary protein structure?

Answer 21

• alpha helix
• beta pleated sheet

Question 22

describe the tertiary structure of a protein

Answer 22

the 3D shape of the protein which is held in place by interactions between R groups

Question 23

what interactions are involved in tertiary protein structure

Answer 23

• ionic bonds
• disulphide bonds
• hydrogen bonds
• hydrophobic/ hydrophilic interactions
• London forces

Question 24

describe quaternary protein structure

Answer 24

• two or more polypeptide chains bonded together by bonds e.g disulphide or ionic

Question 25

what is the structure of a membrane?

Answer 25

• hydrophilic phosphate head
• hydrophobic fatty acid tail

Question 26

what is the model of the membrane structure called?

Answer 26

• fluid-mosaic model

Question 27

what are the 2 main groups of proteins in the membrane

Answer 27

• intrinsic and extrinsic

Question 28

what do the intrinsic proteins have and what are the 3 types?

Answer 28

• has amino acids with hydrophobic R groups
• go through both layers of the membrane

3 types: channel protein, glycoprotein, carrier protein

Question 29

what does the channel protein do

Answer 29

• creates hydrophobic channel
• allows polar ions and molecules to move across membrane

Question 30

what does carrier protein do

Answer 30

• change shape to carry substances across the membrane

Question 31

what does the glycoprotein do

Answer 31

acts as a:
- receptor for messages received by the cell (cell signalling)
- antigen to allow cells to be recognised as self or non-self
- involved in joining cells together (cell adhesion)

Question 32

what are extrinsic proteins

Answer 32

• proteins that have amino acids with hydrophilic R groups on surface

Question 33

how does temperature affect the membrane

Answer 33

higher temp = more energetic molecules = quicker vibrations
the molecules move further apart which makes larger gaps between molecules, making membrane more permeable

Question 34

how do solvents affect membrane

Answer 34

less polar/ non-polar solvents disrupt the membrane
- molecules bind to non-polar hydrophobic tail region, increasing the permeability of the membrane

Question 35

what is the property of water in terms of density?

Answer 35

• less dense as a solid so ice floats
• ice insulates the water below
• allows animals to move & oxygen/ nutrients to circulate