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Biology mark scheme > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

What is cellulose made of (1)

A

beta glucose

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2
Q

What is starch made of (1)

A

alpha glucose

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3
Q

Explain how the structures of starch and cellulose are related to thier functions as storage and structural molecules respectively (4)

A
  • starch is made of amylose and amylopectin joined by alpha 1-4 glycosidic bonds
  • molecules coil in amylose and in amylopectin branch
  • easy to remove glucose molecules
  • cellulose alternate unites rotate by 180 degrees in a straight chain
  • hydrogen bonds froming cross links which gives strength and stability
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4
Q

What is the bond between a glycerol molecule and a fatty acid (1)

A

ester

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5
Q

Describe the type of reaction involved in the breakdown of a monoglyceride (1)

A

hydrolysis

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6
Q

Explain why triglycerides are not considered to be polymers (1)

A

glycerol and fatty acids are different structures

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7
Q

State two functions of triglycerides in a mammal except for energy storage (2)

A
  • portection of internal organs against impact
  • thermal insulation
  • buoynacy
  • waterproofing
  • source of metabolic water
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8
Q

Describe a biochemical test for the presence of glucose in a solution (2)

A
  • add benedicts test and heat
  • colour would change from blue to brick red
  • blue precipitate - neutral
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9
Q

Explain why a positive test would be seen with glucose but not sucrose for benedicts test (1)

A
  • glucose is a reducing sugar
  • reduces copper II sulphate to copper I oxide
  • sucrose is a non reducing sugar
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10
Q

Describe the function of magnesium ions (1)

A

component of chlorophyll

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11
Q

Describe the function of iron ions (1)

A

component of haemoglobin

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12
Q

Describe the function of phosphate ions (1)

A

component of nucleic acids

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13
Q

Describe the function of calicum ions (1)

A

hardens bones / teeth / synaptic transmissions

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14
Q

Name the bond crosslinking cellulose molecule (1)

A

hydrogen

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15
Q

Explain the importance of hydrogen bonds in the role of celluloe in plant cell walls (2)

A
  • holds celluloe chains together to form microfibrils
  • strengthens the cell wall giving structural tability
  • can resist tugor / prevenet cell wall from bursting
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16
Q

Name the chemical reaction by which monomers join together

A
  • condensation
  • polymerisation
17
Q

What is the additional compound in chitin replacing one of the OH groups (1)

A
  • has amino acid
18
Q

State the structural role of chitin in insects and why it is suitable for the role (1)

A
  • exoskeleton
  • strong
  • waterproof
  • light
  • tough
19
Q

Name the storage polysaccharide in animal cells (1)

A

glycogen

20
Q

Name the storage polysaccharide in plant cells (1)

A

starch

21
Q

name the product formed when a triglyceride molecule is broken down (2)

A
  • one glycerol molecule
  • three fatty acid molecules
22
Q

Name the type of bond broken in a triglyceride and the process (2)

A
  • ester
  • hydrolysis
  • chemical insertion of water
23
Q

Describe two functions of lipids in plants (2)

A
  • energy sstroae
  • respiratory substrate
  • source of energy
  • waxy cuticle
  • leaf waterproofing
  • membrane structure
24
Q

State how the structure of a saturated fatty acid differs from the unsaturate fatty acid (2)

A
  • saturates has no double bonds
  • fewer hydrogen atoms in an unsaturated
25
Q

Many amino acids can join in a long chain name the process the molecules join together and the bond formed (2)

A
  • peptide bond
  • condensation
26
Q

Name a sutiable test to show the prescence of amino acids (2)

A
  • add bieurt to test solution
  • blue change to purple is a positive result
27
Q

Suggest a problem that could arise if there were very low concentrations of amino acid present in the solution when performing the biuret test (1)

A
  • little colour change
    purple colour may be masked
28
Q

Describe the inorganic iron present in the haem group (1)

A

iron

29
Q

Why is haemoglobin have a quantenary structure (2)

A
  • four polypeptide chains in tertiary form are combined
30
Q

Name two types of bonds that would be present to maintain polypeptide chain in it teritary structure (2)

A
  • disulphide bridges
  • ionic bonds
  • hydrogen bonds
  • hydrophobic interactions
31
Q

How does the structure of phospholipids differ to triglycerides (2)

A
  • phospholipids have two fatty acids whereas triglycerides have three fatty acids
  • phospholipids have a phosphate head whereas triglucerides do not contain a phosphate head
  • phospholipids have a polar head and non polar tailes whereass triglycerides are non polar
32
Q

Explain the arrangement of phospholipids when near water (2)

A
  • hydrophophillic phosphate heads are attracted to water
  • fatty acids tails are hydrophobic and are repelled by water
33
Q

name the bond broken in a lactose molecule (1)

A

glycosidic

34
Q

name the molecules produced when lactose is broken down (1)

A
  • glucose and galactose

Biology mark scheme (9 decks)

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