[bio] biological molecules Flashcards
definition of condensation reaction
chemical reaction whereby 2 or more simple molecules are joined together to form a larger biological molecule with the removal of water
definition of hydrolysis
splitting up of a complex biological molecules into its component units with the addition of water
bond formed during condensation reaction?
glycosidic bond
elements of carbohydrates
carbon, hydrogen, oxygen
special thing about elements present?
ratio of hydrogen atoms to oxygen atoms is 2:1
3 main groups of carbohydrates
monosaccharides, disaccharides, polysaccharides
examples of monosaccharides
glucose, fructose, galactose
properties of monosaccharides
- generally sweet-tasting
- soluble in water (able to lower water potential in cells)
why do we not store glucose in our bodies?
glucose is a monosaccharide, soluble in water, will lower the water potential of our cells, cells will burst when too much water enters
what happens to excess glucose in our bodies?
excess glucose goes through condensation reaction to form glycogen, which is insoluble in water
examples of disaccharides & their monomers
- maltose - glucose + glucose
- lactose - glucose + galactose
- sucrose - glucose + fructose
types of polysaccharides and their examples and where they are found
storage polysaccharides (starch in plants and glycogen in animals) and structural polysaccharides (cellulose in plants)
why are starch and glycogen suitable as storage polysaccharides
- insoluble in water, won’t affect water potential of cells
- compact, take up less space than individual glucose molecules that make up a glycogen/starch molecule
- too large to diffuse through the cell membrane, hence they will stay in the cell
- easily hydrolysed when needed
structure of starch and glycogen
starch - long straight chains (amylose) or branched chains (amylopectin)
glycogen - highly branched chains
how are storage polysaccharides formed
condensation reaction of large numbers of glucose molecules
structure of structural polysaccharides
can be in long straight/branched chains
properties of cellulose
- insoluble in water
- structure is rigid
- provide mechanical support for the plant
- able to resist expansion when water enters by osmosis
functions of carbohydrates
- forms lubricants like mucus
- forms nectar
- deoxyribose sugar/ribose sugar are used in the formation of nucleic acids like DNA
- glucose is a substrate of respiration
- cellulose forms the supporting structure of plants
elements that make up lipids
carbon, hydrogen, oxygen
number of oxygen as compared to hydrogen and carbon
much less oxygen as compared to carbon and hydrogen
example of lipids
triglycerides and phospholipids
properties of lipids
insoluble in water, but soluble in organic solvents like alcohol
what makes up a triglyceride
3 molecules of fatty acids and 1 molecule of glycerol
what are fatty acids
a long hydrocarbon chain that has a carboxyl functional group (COOH)
difference between saturated and unsaturated fatty acids?
saturated: absence of carbon-carbon double bonds
unsaturated: presence of 1 or more carbon-carbon double bonds
properties of fatty acids
- hydrophobic (do not mix well with water)
- uncharged
composition of glycerol
C3H8O3
what is glycerol?
an alcohol
properties of glycerol
- generally sweet-tasting
- colourless
how are triglycerides formed?
condensation reaction of 3 molecules of fatty acids and 1 molecule of glycerol, removal of 3 water molecules
bond between 1 fatty acid and glycerol?
ester bond
how does ester bond look like? (draw)
O
ll
O - C
properties of triglycerides
compact
insoluble in water
functions of triglycerides
- energy storage
- buoyancy in aquatic animals
- important component of myelin sheath
- protective layer
- heat insulator
- produces metabolic water
- solvent
why energy storage?
contains more carbon-hydrogen bonds per gram than starch/glycogen
1 gram of triglyceride has about twice as much as energy as 1 gram of carbohydrates
light weight energy store —> has about 1/2 the mass of carbohydrates for an equivalent amount of energy stored
where to use as energy storage? (triglyceride)
- oil in seeds in plants for them to travel far in the air
- fats in mammals
- mammals have specialised cells to store fats under their skin
- cells are grouped together to form adipose tissue
- hibernating animals store fats as food reserve
why heat insulator? (triglycerides)
fats conduct heat slowly, excellent heat insulator against heat loss from deeper regions of the body to the outside
where to use as heat insulator? (triglycerides)
huge and thick blubber in polar bears and whales
why buoyancy in aquatic animals? (triglycerides)
triglycerides less dense than water
where to use buoyancy? (triglycerides)
large animals that live in cold seas like whales and seals, they often have very thick layer of blubber
why protective layer? (triglycerides)
ability to absorb shock
where to use as protective layer? (triglycerides)
surrounding delicate and vital organs like heart and kidney
why important component of myelin sheath?
act as electrical insulator to allow rapid transmission of electrical impulses along myelinated neurons
where as important component of myelin sheath? (triglycerides)
nerve cells
why provides metabolic water? (triglycerides)
triglycerides release twice as much water as carbohydrates when oxidases during respiration, because have more hydrogen atoms than carbohydrates, hence a better source of metabolic water
where as metabolic water? (triglycerides)
important for animals like camels and kangaroos that live in the hot and dry desert where water is scarce
why as a solvent?
solvent for fat-soluble vitamins A, D, E, K and other vital substances like hormones
structure of phospholipids
2 molecules of fatty acids (one saturated and one unsaturated)
1 molecule of glycerol
1 phosphate group
function of phospholipids
major component of biological membranes (made up of 2 layers of phospholipids - phospholipids bilayer)
elements in protein
carbon, hydrogen, oxygen and nitrogen
what happens when proteins are heated?
weak bonds in proteins are broken, proteins are denatured, and loses its 3d shape
what are amino acids?
monomers of proteins
how many naturally occurring amino acids are there?
20
structure of amino acid?
every amino acid molecule has a central carbon atom bonded covalently to 4 groups
what are the 4 groups the amino acid molecule is bonded to?
- at least one amino group (NH2)
- a carboxyl group (COOH)
- a hydrogen atom (H)
- a variable group (the R group/the side chain)
structure of the amino acid? (draw out)
H R O
l l ll
N - C - C
l l l
H H OH
formation of polypeptide
amino acids undergo condensation reaction, forms peptide bond after removing water molecules, forms polypeptide
formation of proteins?
polypeptide chain folds into a particular 3D shape as a result of 4 other types of bonds
- disulfide bonds/bridges
- ionic bonds
- hydrogen bonds
- hydrophobic interactions
functions of proteins?
- synthesis of new cells
- biological catalysts
- chemical messenger
- transport proteins
- structural proteins
- defence of body
- source of energy during starvation
how synthesis of new cells?
for growth and repair of new cells
how biological catalysts?
enzymes to speed up rate of chemical reactions
how as chemical messengers?
hormones such as insulin to stimulate target organs to perform a certain function
how as transport proteins?
haemoglobin to transport oxygen in red blood cell
how as structural proteins?
collagen is a component of skin and bones
keratin is a component of hair, nails and feathers
how as defence of body?
antibodies used to help fight infections in the body
how as source of energy during starvations?
oxidised after all the carbohydrates and lipids are used up
