TOPIC 1

• Describe how structure of glycogen is linked to its function

  ( 4 )

  Many glucose monomers means lots of glucose for respiration to release energy,

  Glycogen is highly branched so can be compact,

  Highly branched so more easily hydrolysed into glucose,

  Its large so cannot diffuse out of cell

  Insoluble so doesn't affect water potential
• The three polysaccharides and functions

  ( 3 )

  Starch- Energy storage in Plants

  Cellulose- Cell walls in plants

  Glycogen- Energy storage in Animals

  
• Starch components

  ( 4 )

  Made up of:

  
  

  Amylose- unbranched chain of a-glucose, glycosidic bonds give coiled structure, compact so good for storage,

  
  

  Amylopectin- branched chain of a-glucose, side branches mean enzymes can break glycosidic bonds easier to release glucose quicker

  
• Test for starch

  ( 2 )

  Add iodine dissolved in potassium iodine solution,

  Blue-black colour if present (from orange colour)

  
• Glycogen structure

  ( 2 )

  (Energy storage in animals)

  Animals store glucose as glycogen, it is a polysaccharide of a-glucose.

  Highly branched, stored glucose can be released quicker.

  Compact, so good for storage.
• Cellulose structure

  ( 3 )

  (Cell walls in plants)

  Long, unbranched, and linear chains of beta glucose.

  They are linked by hydrogen bonds to form fibrils.

  It provides structural support.
• Two similarities between starch and cellulose structure

  ( 2 )

  They are both polymers,

  Both contain glucose, hydrogen, and oxygen.

  They both have glycosidic bonds,

  They are 1-4 linked,

  They both have hydrogen bonding within structure.
• Two differences in starch and cellulose structure

  ( 2 )

  Starch has alpha glucose cellulose has beta,

  Starch is compact cellulose is not,

  Starch also has 1-6 bonding cellulose only has 1-4
• (cellulose rotated 180 degrees every other molecule)

  Describe difference shown in image between starch and cellulose.

  ( 2 )

  Starch formed of alpha glucose cellulose formed of beta glucose,

  Position of hydrogen and hydroxyl groups rotates 180 degrees

  
• How is starch adapted to its function in plant cell

  ( 2 )

  Insoluble,

  So doesn't affect water potential.

  (or)

  Its helical,

  So is compact
• How is cellulose adapted for its function in plant cell

  ( 2 )

  Long linear strands,

  become linked by hydrogen bonds to form fibrils,

  Provide strength to cell wall.
• What reducing sugar would you see during chewing

  ( 2 )

  Maltose

  Salivary amylase breaks down the starch.
• Structure of maltose

  ( 3 )

  Two molecules of alpha glucose,

  join by glycosidic bond,

  during condensation reaction.
• In intestine what breaks down Maltose

  ( 1 )

  Maltase
• In humans, enzyme maltase breaks down maltose to glucose.

  Explain why maltase: only breaks down maltose, and allows this reaction to take place at normal body temperature

  ( 5 )

  3D shape of enzyme,

  Active site complementary to maltose,

  The maltose begins to bind to active site of maltase and alter shape of active site ( 3D ) slightly to fit better

  Enzyme lowers activation energy,

  By forming enzyme-substrate complex.
• In the control experiments, cooked wheat chopped up to copy effect of chewing.

  Suggest a more appropriate control experiment.

  ( 2 )

  Add boiled saliva,

  Everything same as experiment but salivary amylase denatured.
• (in graph chewed wheat concentration of sugars increased quicker then chopped up wheat)

  Suggest what these results suggest about effect of chewing on digestion of starch in wheat

  ( 3 )

  Some starch already digested with chewing,

  Faster digestion of chewed starch,

  Same amount of digestion without chewing at end.
• Name the group represented by COOH, in relation to the general formula RCOOH.

  ( 1 )

  carboxyl
• R group of amino acids can be....

  ( 1 )

  Unsaturated or Saturated.

  
• test of lipids in food ( 2 )

  Dissolve in ethanol, add to water, white emulsion forms.
• Test for lipids in liquid ( 2 )

  Shake sample with ethanol, add to water.

  White emulsion forms

  
• test of lipids in seeds ( 3 )


  crush with ethanol, add to water, white emulsion forms
• Properties of fluid mosaic model (for comparison)

  ( 3 )

  -Has a phospholipid bilayer,

  -Cholesterol present in FMM,

  -Phosphate heads point out,

  -Glycoprotein is not present,

  -Has carrier/channel proteins.
• How a triglyceride molecule is formed

  ( 3 )

  One glycerol and three fatty acids,

  Condensation reaction and removes 3 water molecules,

  Ester bonds form.

  
• Triglycerides and water

  ( 1 )

  They are insoluble so don't affect water potential,

  They cause water to enter the cells by osmosis.
• Micelle

  ( 2 )


  Triglycerides clump together as insoluble droplets,

  The tails are hydrophobic so face inwards.

  
• hydrolysis of triglycerides (lipids)

  ( 3/4 )

  Bile salts emulsify lipids,

  Lipase hydrolyses ester bonds, breaking down lipids into monoglycerides and fatty acids,

  In lumen of intestine,

  Fatty acids and monoglycerides pack into micelle.
• Where is lipase produced

  ( 1 )

  In the pancreas, released into the small intestine
• Bond between a glycerol and fatty acid in phospholipid or triglyceride.

  ( 1 )

  Ester Bond
• What is a phospholipid composed of?

  Phosphate group, glycerol, 2 fatty acids.

  
• What are the properties of the phospholipids?

  The phosphate head is hydrophilic and attracts water soluble molecules.

  The fatty acid tails are hydrophobic and do not like water.

  
• If fatty acid is unsaturated...

  ( 1 )

  There is a double bond located between carbon atoms and hydrocarbon chain.

  
• Percentage of lipid in plasma membrane by mass is worked out by...

  ( 2 )

  Divide mass of each lipid by total mass of all lipids,

  Multiply answer by 100
• Cholesterol is used in blood for...

  ( 2 )

  Maintaining shape, giving structural support,

  As red blood cells are free in blood.
• The difference between triglycerides and phospholipids...

  ( 2 )

  Triglycerides have 3 fatty acids but phospholipids have 2,

  one fatty acid is replaced by a phosphate group

  
• Why a fat substitute cant be digested by lipase

  ( 2 )

  Not complementary in shape,

  Unable to bind.
• Describe the primary structure of all proteins

  ( 2 )

  The sequence of amino acids,

  Joined together with peptide bonds to form a polypeptide chain.

  
• Describe the secondary structure of a protein

  ( 2 )

  Hydrogen bonding between amino acids,

  Resulting in either beta pleated or alpha helix structure

  
• Describe the tertiary structure of a protein

  ( 2 )

  ionic (neg and pos atractions) and hydrogen bonding, as well as disulphide bridges (cysteine A.acid)

  This is the final structure for single polypeptides

  
• Describe the quaternary structure of a protein

  Proteins that contain two or more polypeptide chains

  (held together by non-covalent forces) have quaternary structure.

  This is the proteins final structure.