1.1 Carbohydrates Flashcards
What is an organic compound?
- Compound, carbon linked by covalent bonds to each other + hydrogen molecules.
- Large, exist as chains or rings.
What elements do carbon atoms covalently bond with in organic compounds?
- Hydrogen, oxygen, nitrogen + sulfur.
What are the elements included in carbohydrates?
- Carbon, hydrogen + oxygen.
What is the general formula for carbohydrates?
- CnH2nOn.
- Cx(H2O)y.
What are the three types of monosaccharides?
- Trioses (C3H6O3).
- Pentoses (C5H10O5).
- Hexoses (C6H12O6).
What two examples of pentoses (monosaccharides)?
- Ribose + deoxyribose.
What are three examples of disaccharides?
- Sucrose.
- Lactose.
- Maltose.
What is sucrose made from?
- Glucose + fructose.
What is lactose made from?
- Glucose + galactose.
What is maltose made from?
- Glucose + glucose.
What are three examples of polysaccharides and what are their functions?
- Starch (fuel store in plants).
- Glycogen (fuel store in animals).
- Cellulose (major component of plant cell walls).
Why is glucose an important monosaccharide?
- All green leaves manufacture glucose using light.
- Cells use it in respiration (it is a respiratory substrate).
What is the molecular formula of glucose?
- C6H12O6 (hexose).
What is a isomer?
- 2 or more different structural formulae of the same molecular formula.
What are the 2 isomers of glucose?
- Alpha glucose.
- Beta glucose.
What is the structural formula of alpha glucose?
CH2OH
|
H C — O H
\ / \ /
C OH H C
/ \ / \ / \
OH C — C OH
/ \
H OH
What is the structural formula of beta glucose?
CH2OH
|
H C — O OH
\ / \ /
C OH H C
/ \ / \ / \
OH C — C H
/ \
H OH
What is the structural formula of pentose ribose?
. O
CH2OH / \ OH
| / \ |
C H H C
| \ | | / |
H C — C H
| |
OH OH
What is a condensation reaction?
- Reaction where two molecules are chemically linked w elimination of a water molecule.
- Catalysed by an enzyme.
What is the bond between monosaccharide residues after the condensation reaction to form a disaccharide?
- Glycosidic bond.
- Strong, covalent bond.
What is a hydrolysis reaction?
- Reaction in which a molecule of water is used in breaking a chemical bond.
- Reverse of condensation.
- uses enzyme asw, but diff enzyme.
How is maltose formed?
- Condensation reaction of 2 glucose molecules.
How is lactose formed?
- Condensation reaction of galactose + glucose.
How is sucrose formed?
- Condensation reaction of glucose + fructose.
How is a polymer defined?
- Large molecule comprising repeated, identical smaller molecules (monomers) linked together by chemical bonds.
Which polysaccharides function as fuel stores?
- Glycogen + starch.
Which polysaccharide has a structural function and how does its structure affect it?
- Cellulose.
- Has huge molecules - not easily hydrolysed by enzyme action.
What two polysaccharides is starch a mixture of?
- Amylose - unbranched chain of α-glucose residues.
- Amylopectin - branched chain of α-glucose residues.
How does the shape of starch form?
- Helix - glycosidic bonds between α-glucose residues.
- Stabilised by lots of hydrogen bonds between parts of the component glucose residues.
What is a residue?
- When monomers are linked into polymer - no longer called molecules, now called residues.
Where is starch used and how is it used?
- Storage carb in plants.
- Laid down as compact grains.
Why is the structure of starch useful?
- Molecules are compact + insoluble.
- ready hydrolysed to form sugar when required (enzymes are involved).
How do we test for the presence of starch?
- Adding solution of iodine in potassium iodide.
- Iodine molecules fit neatly into centre of starch helix, creating blue-black colour.
What is glycogen a polymer of?
- α-glucose.
- Similar to amylopectin but larger and more branched.
Where can glycogen be found?
- Granules seen in liver cells and muscle fibres under e- microscope.
- Can be seen throughout whole body apart from brain.
When do we draw our glycogen reserves?
- During prolonged and vigorous exercise.
- Once these are exhausted, body starts to metabolise fat.
What is a cellulose polymer made up of?
- 2000 to 3000 units of beta-glucose.
How do beta-glucose molecules join together?
- The way glycosidic bonds form causes adjacent β to be upside down w respect to each other.
- referred to as 1-4 glycosidic bonds.
How does the bond of β-glucose affect the structure of cellulose?
- Arrangement leads to cellulose molecules being long, straight chains.
- 200 of these chains naturally become packed into fibres, held together by hydrogen bonds.
How is the strength of plant cell walls created?
Combined effect of:
- Bonds between β-glucose monomers,
- Hydrogen bonds between + within β-glucose chains,
- Way in which fibres are arranged in different directions.
