chapter 2 - biological molecules Flashcards
monomer
basic building block
polymer
made from many similar repeating monomers
macromolecule
large biological molecule (e.g. protein, polysaccharide)
why lipids are not polymer?
they are made from two different types of monomers (glycerol and fatty acids)
carbohydrates general formula
Cx(H2O)y
monosaccharides
sugars (CH2O)
glucose molecular formula
C6H12O6
isomers
biological molecules that have the molecular formula but different structural formula
alpha-glucose
-OH group on carbon atom 1 is below the ring
beta-glucose
-OH group on carbon atom 1 is above the ring
roles of monosaccharides
source of energy (due to large CH bonds) and building blocks
disaccharides
two monosaccharides joining together
maltose
glucose + glucose
sucrose
glucose + fructose
lactose
glucose + galactose
condensation reaction
the joining of two monosaccharides which releases a molecule of water
1-4 glycosidic bond
the glycosidic bond formed during a condensation reaction between carbon atom 1 and 4
polysaccharides
not sugars
why glucose is stored as polysaccharides
glucose is soluble and reactive -> would affect the cell’s osmotic properties
starch
amylose and amylopectin
amylose
alpha-glucose; long and unbranching chain of alpha-1-4 linked
curved and coiled up chains -> more compact, can pack more into a molecule
amylopectin
more branched and shorter chains of alpha-1-4 linked with 1-6 linkages
glycogen
alpha-1-4 linked with alpha-1-6 linkages forming branches; more branched -> more sites for enzyme attachments and easier access for glucose
cellulose
beta-glucose -> glucose molecules must be rotated 180 degrees relative to the other
why does cellulose have a high tensile strength?
because the arrangement of beta-glucose molecules allowed hydrogen atoms of -OH groups to create hydrogen bonds with oxygen atoms in the same right, and oxygen atoms in neighbouring -OH groups
structural function of cellulose
high tensile strength -> difficult to stretch or break and so it can withstand large pressure (osmosis)
formation of hydrogen bonds
slightly negative oxygen atom is attracted to with slightly positive hydrogen atoms
dipole
unequal distribution of charge, only occurs when there is an -OH, -CO or -NH group
fatty acids
contain the acidic carboxyl group (head) and long hydrocarbon tails
unsaturated fatty acid
contains double bonds of carbon -C=C- : do not contain the maximum amount of hydrogen
carbon double bond
a kink if formed wherever there is a double bond. this pushes the chains further apart, weaker intermolecular forces and hence lower boiling point
unsaturated vs. saturated
unsaturated fats (e.g. avocado) is perceived as better
alcohol
a series of organic molecules which contain a hydroxyl group attached to a carbon atom
ester
the reaction between an acid and an alcohol
ester bond
chemical link between the acid and alcohol (from a condensation reaction)
triglyceride
three fatty acid tails, three ester bond and an acidic head; non-polar
roles of triglycerides
energy reserves (more CH bonds than carbohydrates -> mass:energy ratio)
insulator against loss of heat
metabolic source of water (when oxidised in respiration)
phospholipid
hydrophilic phosphate head and hydrophobic fatty acid tails -> amphipathic
amino acids
a basic amine group -NH2 and an acidic carboxyl group -COOH
R groups
one in 20 differnt amino acids
peptide bond
formed during a condensation reaction: one loses a hydroxyl group from its carboxyl group, the other loses a hydrogen atom from its amine group -> carbon bonds with nitrogen
primary structure
the sequence of amino acids in a chain
secondary structure
the coiling and folding of amino acid chains
alpha-helix and beta-pleated sheet
due to hydrogen bonding between the oxygen of the -CO- group and the hydrogen of the -NH- group of the amino acid four places ahead of it
tertiary structure
three dimensional coiling of already folded amino acid chains
roles of tertiary shape
determines the shape of the molecule by precise bonds
bonds in tertiary structure
hydrogen bonds, disulfide bonds (cysteine), ionic bonds and hydrophobic interactions
quarternary structure
how polypeptide chains are arranged in a protein molecule
globular protein
curl up into a ball shape (myoglobin), hydrophobic R groups are point inwards, while hydrophilic R groups remain on the outside -> soluble
haemoglobin - globular
functional protein, four globin (two alpha and two beta), four haem groups
anaemia
one amino acid in the beta chain is replaced with another (from a polar to a non-polar) -> less soluble
prosthetic group
an important and permanent part of a protein that is not made of amino acids
fibrous protein
curl up into long strands, insoluble in water, structural protein
collagen - fibrous
found in skin, tendons, bones; three helix polypeptide chains are held together by hydrogen bonds (glycine - every third amino acid - smallest); covalent bonds form between the R groups of amino acids next to each other -> fibrils -> fibres
roles of collagen
flexible but tremendous tensile strength
water as a solvent
solvent for ions and polar molecules (medium for metabolic reactions)
water as a transport medium
in blood, lymphatic, excretory…
high specific heat capacity
the amount of heat required to raise the temp of 1kg of water by 1 degrees
water has a high heat capacity
hydrogen bonds make it difficult for molecules to move freely -> allows water to store more energy
more resistant to temperature changes (more constant the air surrounding)
high latent heat of vapourisation
high -> living organisms can use evaporation as a cooling mechanism (sweating) - a large amount of heat can be lost for little loss of water
density and freezing properties
ice insulates the water underneath it -> reduces the tendency for large bodies of water to freeze completely
