2.3 - Carbohydrates and lipids

Cards (36)

  • Glucose:
    • Has the formula C6H12O6
    • It forms a hexagonal ring (hexose)
    • Glucose is the form of sugar that fuels respiration
    • Glucose forms the base unit for many polymers
  • Glucose:
    A) CH2OH
    B) O
  • Alpha glucose Formation: DDUD
  • Beta glucose formation: UDUD
  • Galactose:
    • Formation: UDUU
    • A hexose sugar
    • Formula C6H12O6 but is less sweet
    • Most commonly found in milk but also found in cereals
  • Fructose:
    • A hexose sugar
    • Commonly found in fruits and honey
    • It is the sweetest naturally occurring carbohydrate
  • Fructose
    A) CH2OH
    B) CH2OH
    C) Fructose
    D) OH
    E) OH
    F) OH
    G) O
  • Ribose:
    A) CH2OH
    B) OH
    C) O
    D) OH
    E) OH
  • Ribose:
    • A pentose sugar, it has a pentagonal ring
    • It forms the backbone of RNA
    • Deoxyribose differs as shown in the diagram with a H
  • Monosaccharides are the monomers of polysaccharides
  • Maltose:
    • A dimer of glucose
  • Lactose:
    • A dimer of glucose and galactose
    • most commonly found in milk
  • Sucrose:
    • A dimer of glucose and fructose
    • Known as table sugar
  • Polysaccharides:
    • contain more than 2 molecules
    • Often very long and branched
    • Glycosidic bonds can be 1-4 or 1-6
  • Cellulose:
    • Cellulose is made by linking together β-glucose molecules.
    • Condensation reactions link carbon atom 1 to carbon atom 4 on the next B-glucose.
    • The glucose subunits in the chain are oriented alternately upwards and downwards.
    • The consequence of this is that the cellulose molecule is a straight chain, rather than curved.
  • Cellulose:
    • Cellulose molecules are unbranched chains of B-glucose.
    • Hydrogen bonds link the the molecules together.
    • The linked molecules form bundles called cellulose microfibrils.
    • They have very high tensile strength.
    • The tensile strength of cellulose (the basis of cell walls) prevents plant cells from bursting, even under very high (water) pressure.
  • Starch structure:
    • Starch is made by linking together a-glucose molecules
    • Condensation reactions link carbon atom 1 to carbon atom 4 on the next a-glucose
    • All the glucose molecules in starch can be orientated in the same way
    • The consequence of this is that the starch molecule is curved, rather than straight.
    • Size of the molecule is not fixed
  • Starch Function:
    • Starch is only made by plant cells.
    • Molecules of both types of starch are hydrophilic but are too large to be soluble in water.
    • Starch does not affect the osmotic balance of cells,
    • It is easy to add or remove extra glucose molecules to starch
    • Therefore starch is useful in cells for glucose, and consequently energy, storage.
    • In seeds and storage organs such as potato cells glucose is held as starch.
    • Starch is made as a temporary store in leaf cells when glucose made faster by photosynthesis than it can be exported to other parts of the plant.
  • Amylopectin:
    • The chain is branched, so has a more globular shape.
    • Due it’s branched nature amylopectin can be much larger consisting of 2,000-200,000 units
  • Amylose:
    • The chain of α-glucose molecules is un-branched and forms a helix.
    • Typically amylose is made up of 300-3,000 glucose units
  • Glycogen:
    • The molecule varies in size, typically it consists of 30,000 units
    • Glycogen is not just a simple chain, it branches many times
    • Condensation reactions link carbon atom 1 - 4 on the next  α-glucose.
    • Branches occur where a condensation reaction instead links carbon atom 16.
    • As a result the molecule is compact
  • Glycogen:
    • Glycogen does not affect the osmotic balance of cells, i.e. cause too much water to enter them
    • It is easy to add or remove extra glucose molecules to starch
    • Therefore glycogen is useful in cells for glucose, and consequently energy, storage.
  • Glycogen:
    • Glycogen is made by animals and also some fungi.
    • It is stored in the liver and some muscles in humans.
    • It is used in cells where large stores of dissolved glucose would cause osmotic problems.
  • Fatty acid:
    A) CH3
    B) CH2
    C) COOH
  • Types of fatty acids:
    A) Saturated
    B) Monounsaturated
    C) Polyunsaturated
  • Cis-isomers:
    • Very common in nature
    • The hydrogen atoms are on the same side of the two carbon atoms
    • The double bond causes a bend in the fatty acid chain
    • Therefore cis-isomers are only loosely packed
    • Triglycerides formed from cis-isomers have low melting points – they usually liquid at room temperature
  • Trans-isomers:
    • Rare in nature – usually artificially produced to produce solid fats, e.g. margarine from vegetable oils.
    • The hydrogen atoms are on opposite side of the two carbon atoms
    • The double bond does not causes a bend in the fatty acid chain
    • Trans-isomers can be closely packed
    • Triglycerides formed from trans-isomers have high melting points – they usually solid at room temperature
  • Isomers
    A) CIS-ISOMER
    B) TRANS-ISOMER
  • Triglyceride:
    A) H
    B) H
    C) H
    D) C
    E) OH
    F) GLYCEROL
    G) 3 FATTY ACIDS
    H) Triglyceride
    I) ester bond
  • Lipid functions:
    • Structure:  Phospholipids are a main component of cell membranes
    • Hormonal signalling:  Steroids are involved in hormonal signalling (e.g. estrogen, progesterone, testosterone)
    • Insulation:  Fats in animals can serve as heat insulators while sphingolipids in the myelin sheath (of neurons) can serve as electrical insulators
    • Protection:  Triglycerides may form a tissue layer around many key internal organs and provide protection against physical injury
    • Storage of energy:  Triglycerides can be used as a long-term energy storage source
  • Lipid energy storage:
    • Lipids are normally used for long-term energy storage whereas carbohydrates are used for short-term energy storage
    • The lipids that are used are fats.
    • They are stored in specialized groups of cells called adipose tissue.
    • Adipose tissue is located immediately beneath the skin and also around some organs including the kidneys.
  • Reasons for using lipids for long-term energy storage:
    • The amount of energy released in cell respiration per gram of lipids is double that for carbohydrates (and protein)
    • Lipids add 1/6 as much to body mass as carbohydrates: fats are stored as pure droplets whereas when 1g glycogen is stored it is associated with 2g of water.
    • This is especially critical for active animals as energy stores have to be carried.
  • Why is glycogen needed?
    • This is because glycogen can be broken down to glucose rapidly
    • Then can be transported easily by the blood to where it is needed
    • Fats in adipose tissue cannot be mobilized as rapidly
    • Glucose can be used either in anaerobic or aerobic cell respiration whereas fats and fatty acids can only be used in aerobic respiration
  • Glycogen:
    • The medium-term energy storage molecule in animals. It is stored in the liver and muscles. The energy stored in glycogen is more readily available than the energy stored in fat.
  • Glucose:
    • Is in the bloodstream for immediate use and will either be used in respiration to yield ATP or converted to glycogen or fat
  • BMI=BMI=Mass(kg)/(height(m))2Mass(kg)/(height (m))^2