12.1 Carbs and Lipids

Question 1

Monomer

Answer 1

A monomer is a smaller / repeating) unit / molecule from which larger molecules / polymers are made;

Question 2

Polymer

Answer 2

• Large molecules made from joining many identical monomers together
• Formed via a condensation reaction

Question 3

Condensation reaction

Answer 3

Removal of water to form bond for polymer and byproduct of water

Question 4

Hydrolysis reaction

Answer 4

Addition of water to break bond in polymer

Question 5

Alpha glucose

Answer 5

6 carbon
12 hydrogen
6 oxygen
OH point downwards- parallel

Question 6

Beta glucose

Answer 6

6 carbon
12 hydrogen
6 oxygen
One OH points up one points down- diagonal

Question 7

Bond between 2 glucose molecules

Answer 7

Glycosidic bond

Question 8

Water is removed from where to form glycosidic bond

Answer 8

H removed from one glucose and OH removed from the other

Question 9

Monosaccharide examples

Answer 9

Glucose (penguin)
Galactose (rave)
Fructose (witch’s hat)

Question 10

Disaccharide examples

Answer 10

Maltose
Sucrose
Lactose

Question 11

Disaccharide formula

Answer 11

C12 H22 O11

Question 12

Polysaccharide examples

Answer 12

Glycogen
Starch
Cellulose

Question 13

Maltose

Answer 13

Alpha glucose and alpha glucose
Maltase enzyme

Question 14

Lactose

Answer 14

Galactose and alpha glucose
Lactase enzyme

Question 15

Sucrose

Answer 15

Fructose and alpha glucose
Sucrase enzyme

Question 16

Glycogen

Answer 16

• Only found in animals
• Alpha glucose
• Shorter chains SO more readily hydrolysed into glucose
• Highly branched
• Larger surface area
• Stored in muscle and liver
• Insoluble SO does not affect water potential

Question 17

Amylose

Answer 17

• Carbon 1:4 glycosidic bonds SO long and linear chains of alpha glucose with coil into a helix
• Compact SO good for storage
• Insoluble SO does not affect water potential
• Large SO does not diffuse out of cell

Question 18

Two types of starch

Answer 18

Amylose
Amylopectin

Question 19

Amylopectin

Answer 19

• Branched chain of alpha glucose
• Carbon 1:4 and 1:6 glycosidic bonds
• Provides a large surface area FOR rapid hydrolysis by enzymes to release glucose for respiration
• Insoluble SO does not affect water potential
• Large SO does not diffuse out of cells

Question 20

A starch molecule has a spiral shape. Explain why this shape is important to its function in cells.

Answer 20

Compact/occupies small space/tightly packed;

Question 21

The structure of cellulose is related to its role in plant cell walls. Explain how. (3)

Answer 21

• Long, straight, unbranched chains of Beta glucose;
• (Joined by) many WEAK hydrogen bonds;
• Form microfibrils / macrofibrils;
• Provide rigidity/strength/support;

Question 22

Cellulose

Answer 22

• Only found in plants
• Beta glucose
  -Made of B-glucose molecules join together via condensation reactions to form long unbranched chains
• Every other b-glucose molecule rotates 180 degrees to allow carbon 1 and 4 to be adjacent to form a GLYCOSIDIC BOND
• Several chains are joined via weak hydrogen bonds to form microfibrils

Question 23

Hydrogen bonds are important in cellulose molecules. Explain why.

Answer 23

• Holds chains/cellulose molecules together/forms cross links between chains/cellulose molecules/forms microfibrils;
• Providing strength/rigidity (to cellulose/cell wall);
• Weak Hydrogen bonds provide strength in large numbers;

Question 24

Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein

Answer 24

• Glucose and galactose
• Joined by condensation
• Joined by glycosidic bond
• Added to polypeptide in Golgi

Question 25

Describe how the student would show that reducing sugars were present in a solution.

Answer 25

1. Add Benedict’s; 2. Heat to 95°C; 3. Red/orange/yellow/green precipitate (shows reducing sugar present);

Question 26

Describe how the student would show that non- reducing sugars were present in a solution. (sucrose)

Answer 26

1. Test using Benedict’s test to show a no colour change 2. Add HCL to a fresh sample 3. Boil to hydrolyse glycosidic bonds 4. Neutralise the solution by adding solid sodium hydrogen carbonate 5. Test using Benedict’s reagent to show a red precipitate

Question 27

Test for unknown conc. of reducing sugars

Answer 27

1. Make up several know conc of reducing sugar 2. Carry out the Benedict’s test 3. Use a colorimeter to measure the colour of each solution and plot using a calibration curve 4. CONC ON X AND ABSORBANCE ON Y 5. Find the concentration of the sample using the calibration curve

Question 28

Describe how you would test a sample of food for the presence of starch.

Answer 28

1. Add potassium iodide (KI) solution to the food sample; 2. Blue/black/purple indicates starch is present;

Question 29

Describe how you would test a liquid sample for the presence of lipid box and how you would recognise a positive result.

Answer 29

1. (Mix / shake sample) with ethanol, then water and shake; 2. Cloudy White / milky (emulsion);

Question 30

Triglycerides found in...

Answer 30

food

Question 31

Phospholipids help to...

Answer 31

form cell membrane of cell

Question 32

Types of lipids

Answer 32

Triglycerides Phospholipids

Question 33

Triglyceride structure

Answer 33

1 glycerol head 3 fatty acid tails Ester bond Condensation reaction

Question 34

Saturated fatty acid definition

Answer 34

NO double bonds between carbon atoms within the hydrocarbon chain

Question 35

Unsaturated fatty acid definition

Answer 35

At least 1 double bond between carbon atoms within the hydrocarbon chain

Question 36

Triglyceride properties

Answer 36

- Insoluble in water SO do not affect water potential - Low mass:energy ratio SO good stores of energy - High hydrogen:water ratio SO good sources of water

Question 37

Phospholipids

Answer 37

- Similar structure to triglycerides - One fatty acid replaced by a phosphate group - Phosphate group is polar

Question 38

Compare and contrast the structure and properties of triglycerides and phospholipids

Answer 38

* Both contain ester bonds * Both contain glycerol * Fatty acids on both may be saturated or unsaturated * Both are insoluble in water * Both contain C, H and O but phospholipids are also contain P * Triglyceride has three fatty acids and phospholipids have two fatty acids plus phosphate group * Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region * Phospholipids form monolayer/micelle/bilayer but triglycerides don’t.

Question 39

Describe the biochemical tests you would use to confirm the presence of lipid, non-reducing sugar and amylase in a sample.

Answer 39

Lipid 1. Add ethanol/alcohol then add water and shake/mix OR Add ethanol/alcohol and shake/mix then pour into/add water; 2. White/milky emulsion OR emulsion test turns white/milky; Non-reducing sugar 3. Do Benedict’s test and stays blue/negative; 4. Boil with acid then neutralise with alkali; 5. Heat with Benedict’s and becomes red/orange (precipitate); Amylase 6. Add biuret (reagent) and becomes purple/violet/mauve/lilac; 7. Add starch, (leave for a time), test for reducing sugar/absence of starch;

Question 40

A student carried out the Benedict’s test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution.

Answer 40

1. Filter and dry (the precipitate); 2. Find mass/weight;

Question 41

Lipid functions (extra)

Answer 41

- Conduct heat slowly SO good thermal and electrical insulators - Stored around delicate organs such as kidneys to protect them

Question 42

Lipids

Answer 42

- Triglycerides found in food - Phospholipids help to form the cell membrane of a cell