B1.1 Carbohydrates and lipids Flashcards
Describe the condensation reaction
- Combines 2 molecules, releasing a water molecule
- Many repeated condensation reactions btwn monomers produce polymers (e.g. monosaccharide to polysaccharides)
state/describe monosaccharides
- quite soluble
- Made of carbon, hydrogen, oxygen
[Glucose, Galactose, Fructose] - Hexoses (6-carbon atoms), isomers of C6H12O6
[Ribose, Deoxyribose] - Pentoses (5-carbon atoms), C5H10O5 and C5H10O4 respectively
state/describe disaccharides
(2 monosaccharides joined by condensation reaction), soluble
- sucrose (glucose+fructose)
- maltose (glucose+glucose)
- lactose (glucose+galactose)
state/describe polysaccharides
Polymers of monosaccharides, low solubility
ENERGY STORAGE MOLECULES
Starches (found in plants, for short-term storage):
- Amylose (unbranched)
- Amylopectin (branched)
Fibres (indigestible by humans):
- Cellulose (insoluble)
- Pectins (soluble)
Glycogen (storage form of glucose in animals)
- highly branched polymer of glucose w many side branches
- Stored in liver and muscles
Describe the structure of amino acids
- each central C atom has attached to it:
- a hydrogen atom
- a r group (1 of 20)
- amino group (NH2)
- a carboxylic acid group (COOH)
amino acid > dipeptide > polypeptide
structure of nucleic acids
phosphate + ribose sugar + nitrogenous base
nucleic acid (monomer)> polynucleic acid (polymer)
Describe hydrolysis reactions
The addition of a water molecule to break down a large molecule. Water is split into O and OH groups which are incorporated to produce monomers.
e.g. the breaking down of macromolecules to their monomers by a series of hydrolysis reactions
Properties and uses of glucose
- soluble
- relatively small
- transportable in blood, dissolved in plasma
- chemically very stable (like most carbohydrates) = useful for food storage. However, this would cause osmotic problem in cells if stored in large quantities and is hence converted to glycogen/starch
- glucose yields energy when oxidised = used as a substrate in respiration
Starch in plant cells (structure, properties)
- Starch is a mixture of unbranched amylose (1, 4 glycosidic bonds) and branched amylopectin (shorter chains of linked 1, 4 a-glucose units, but with branch points of 1,6 glycosidic bonds along the chains.)
- The bonds btwn glucose molecules bring the molecules together as a helix
- the whole starch molecule is stabilised by countless Hydrogen bonds btwn parts of component glucose molecules.
- Glycogen is a polymer of alpha-glucose (chemically very similar to amylopectin, although larger and more highly branched)
Practice drawing a-glucose, b-glucose, galactose
good luck
How are energy stores built/mobilised?
Build: a-glucose molecules are added by condensation
Mobilised: a-glucose molecules are removed by hydrolysis
Structure of cellulose (fibre)
- a polymer of glucose that forms microfibrils
- Indigestible by most animals (enzymes that digest starch by hydrolysing a-glucose linkages are unable to hydrolyse b-glucose linkages)
- ALTERNATING ORIENTATION of b-glucose monomers, resulting in STRAIGHT CHAINS that can be grouped into bundles and CROSS-LINKED with HYDROGEN BONDS
Glycoproteins for cell recognition example
ABO antigens in red blood cells - play a role in blood transfusion
Remember -
- RECEIVING blood, as long as the RBC has the antigen it can receive blood from that blood type, and O can always be received. E.g. AB can receive blood from A, B, AB, O
- DONATING blood, as long as ONE antigen is present in both blood types can donate. O can donate to everyone. e.g. B can donate to B, AB.
Properties and types of lipids
- only soluble in non-polar solvents
- sparingly soluble in polar solvents
- hydrophobic = does not dissolve in water. This is as lipids consist mostly of hydrocarbons, which form non-polar covalent bonds
- Triglycerides (fats [solid at 20c] and oils [liquid at 20c])
- Steroids [liquid at 20c]
- Waxes
- Phospholipids
Formation of triglycerides
Condensation reaction between glycerol backbone and 3 fatty acids
Formation of phospholipids
Condensation reaction btwn glycerol backbone and 2 fatty acids. Phosphate group attached in place of the third fatty acid.
Fatty acids are non-polar hydrophobic, phosphate group is polar hydrophilic
structure of fatty acids + Diff btwn unsaturated and saturated fatty acids
All fatty acids consist of a carboxyl (COOH) group, the hydrocarbon chain, and the methyl group (CH3).
Unsaturated fatty acids have one or more double bonds btwn carbons (e.g. oil)
Saturated fatty acids have no double bonds btwn carbon atoms (e.g. butter)
How does unsaturated vs saturated affect melting point in triglycerides?
Triglycerides with unsaturated fatty acids have lower melting points than triglycerides with saturated fatty acids
Unsaturated fatty acids have bends in their hydrocarbon tails = reduce density and lowers melting points. Oils generally have shorter fatty acid tails
Saturated fatty acids with saturated bonds = more densely packed, increases melting point. Fats generally have longer fatty acid tails.
Plants usually have unsaturated fatty acids, animals usually have saturated fatty acids
Difference btwn monounsaturated and polyunsaturated fatty acids
poly = 2 or more h bonds
mono = 1 h bond
Where are triglycerides found and what are their properties?
In animals, triglycerides are found in adipose tissue
- chemically very stable = v little energy lost over time
- immiscible in water = oil droplets formed in the cytoplasm, does not have an osmotic effect
- good insulators of heat = thermal insulator to conserve body heat
- release x2 energy compared to carbohydrates = energy stored in 1/2 the body mass
Examples of non-polar steroids passing through phospholipids bilayer (2) and why
Oestradiol and testosterone
The hydrophobic properties of these enzymes enable them to be soluble in the fatty acid layers of the membranes.
Identifying steroids
4 carbon rings attached to one another NOT 4-carbon rings
Structure/properties of waxes
Long chain fatty acid bound to long chain alcohol
- high melting point
- waterproof
- resistant to degradation
