Carbohydrates

Question 1

What are the three types of saccharides ?

Answer 1

1. Monosaccharides - A single sugar molecule.
2. Disaccharide - Two monosaccharides.
3. Polysaccharide - Many monosaccharides.

Question 2

How can monosaccharides join together to form disaccharides and polysaccharides ?

Answer 2

Through glycosidic bonds which are formed on condensation reactions.

Question 3

Give 2 examples of Monosaccharides

Answer 3

1. Glucose :
   
   • Contains 6 carbon atoms and is the main
     substrate for respiration.
     Isomers :
   • Beta glucose (plants)
   • Alpha glucose (Animals)
2. Ribose :
   
   • Contains 5 carbon atoms.
   • Pentose sugar.
   • Component of DNA and RNA.

Question 4

Name me the 3 Disaccharides.

Answer 4

1. Maltose = Glucose + Glucose
2. Sucrose = Glucose + Fructose
3. Lactose = Glucose + Galactose

Question 5

Blurt everything you know about glycogen.

Answer 5

• Main energy storage molecules in animals.
• Formed by many molecules of alpha glucose.
• Joined together by 1,4 and 1,6 glycosidic bonds.
• Has are large number of side branches meaning that energy can be hydrolysed and energy can be released quickly.
• Relatively large but compact, which maximises the amount of energy it can store.

Question 6

Blurt everything you know about starch.

Answer 6

• Starch is made up of amylose and amylopectin (two polysaccharides).
• Amylose :
  - Unbranched chain of glucose molecules joined
  1,4 glycosidic bonds. It coiled and compact so
  store a lot of energy.
• Amylopectin :
  - Branched and made up of glucose molecules
  joined together by 1,4 and 1,6 glycosidic bonds.
  Due to the presence of any side branches it can
  be rapily hydrolysed and release energy
  quicker. It’s also compact so can store lots of
  energy.

Question 7

Name the 2 types of lipids.

Answer 7

• Biological molecules which are only soluble in organic solvents such as alcohols.
• Saturated lipids :
  - Found in animal fats.
  - Don’t contain any carbon to carbon double
  bonds.
  - Solid at room temp.
• Unsaturated lipids :
  - Found in plants.
  - Contain the Carbon to carbon double bond.
  - Melt at lower temperatures than saturated
  fats.
  - Liquid at room temp.

Question 8

Why do unsaturated lipids have a lower melting point ?

Answer 8

They have weaker intermolecular forces. The double bonds in the unsaturated lipids reduce the strength of these **intermolecular forces* * as they create a kink in the hydrocarbon, so molecules cannot pack together as closely.

Question 9

Name some properties of lipids.

Answer 9

• Waterproof because their fatty tail is hydrophobic.
• Non-polar and insoluble in water. Therefore are good for storage as they do not interfere with water based reaction in the cytoplasm.
• Conduct heat slowly therefore they provide thermal insulation.

Question 10

Blurt everything you know about triglycerides.

Answer 10

• Made up of one molecule of glycerol and three fatty acids joined by ester bonds formed in condensation reactions.
• Triglycerides are used as energy reserves in plants and animal cells.

Question 11

Blurt everything you know about phospholipids .

Answer 11

• Hydrophilic phosphate head attached to 2 hydrophobic tail.
• Ester bonds
• This results in a phospholipid bilayer in the cell membrane as heads face watery environment whereas tails move away from them.

Question 12

Name the two type of lipoproteins.

Answer 12

Lipoproteins transport cholesterol in the body.

1. High density lipoproteins (HDL - good cholesterol) :
   
   • formed from unsaturated fats, protein and
     cholesterol.

transports excess cholesterol from the bloodstream to the
liver where it’s broken down, It reduces
the risk of atherosclerosis. It’s generally
associated with lower risk of heart disease.
Regular exercise, healthy diet and not smoking
can increase HDL levels.

2. Low density lipoprotein (LDL - bad’ cholesterol) :
   
   • Formed from saturated fats, protein
     and cholesterol and transports
     cholesterol from the liver to the blood,
     thus causing the cholesterol level to increase,
     hence why it is linked to atherosclerosis.

Question 13

Describe the correlations in lipoproteins.

Answer 13

There’s a correlation between high levels of saturated fats and high blood cholesterol.
saturated fats are one of the components of LDL.

However, the link between cholesterol and CVD is causal because cholesterol is involved in plaque formation.