biological molecules Flashcards
(18 cards)
Water (hydrogen bonds)
Polar (slight negative oxygen slight positive hydrogen)
-excellent solvent as it can form hydrogen bonds
-high latent heat of evaporation lot of energy used to convert to gas
-high specific heat capacity high boiling point due to many hydrogen bonds
Carbohydrates
Long chain sugar molecules
condensation reaction when joined
a molecule of h2o removed, glycosidic bond forms
hydrolysis required to break glycosidic bond
glucose
Hexose sugar (made up of 6 carbons)
Can exist as alpha or beta glucose
Alpha - the hydrogen atom is Above the carbon.
Beta - the hydrogen atom is Below the carbon.
Ribose
monosaccharide
component of RNA molecules
a pentose sugar with five carbon atoms in the ring
Starch
Broken down by plants when energy needed
Exists in 2 different forms, amylose and amylopectin
Amylose
unbranched spiralling chains of alpha-glucose molecules
Its coiled structure means that it is very compact so lots of amylose can be packed into a cell
Amylopectin
branched chains of alpha-glucose molecules
Its branches increase its surface area which means that enzyme can quickly break it apart when glucose is needed for respiration
Cellulose
long unbranched chains of beta-glucose molecules
Multiple chains are linked together by hydrogen bonding to form strong structures called micofibrils
The strong microfibrils in the cell wall help to give plant cells their shape and structural support
Glycogen
branched chains of alpha glucose, similar to amylopectin but with more side-branches
This gives it a large surface area for enzyme action to release glucose when energy is needed
It is more compact that amylopectin, which means more can be stored in a cell
Lipids
Synthesis of phospholipid or triglyceride forms a ester bond by condensation reaction
Broken apart by hydrolysis
Triglyceride
Used as an energy store as a lot of energy released when ester bonds are hydrolysed
Inside cells triglycerides group to form lipid droplets with hydrophobic tails inwards and hydrophilic heads outwards
These insoluble droplets make good energy storage molecules since they do not affect the osmotic potential of the cell
Phospholipid
Main component of cell membrane
Form a phospholipid bilayer with hydrophilic heads outward and hydrophobic tails inwards to form a barrier to prevent polar molecules from entering or leaving the cell
Cholesterol
Also found in cell membranes and strengthens it
Pushes hydrophilic heads and hydrophobic tails closer together to make cell membrane more rigid
Proteins
Polymers of amino acids joined by peptide bonds
consist of a central carbon atom attached an amine group, a hydrogen atom a carboxyl group and an ‘R’ group which is different in each amino acid
Structure of protein
the polypeptide undergoes multiple stages of folding
-Primary structure, peptide bonds formed between amino acids
-Secondary structure, hydrogen bonds form nearby amino acids to form either an alpha helix or a beta pleated sheet
-Tertiary structure, more bonds form between the different R groups to give the protein a 3D structure
-Quaternary structure, interaction of multiple polypeptide chains held together by bonds
Globular proteins
Spherical
hydrophobic amino acids tucked inside hydrophilic amino acids exposed outside
Soluble and can be transported easily
unravel and denature when the temperature or pH deviates from optimum levels
Fibrous protein
long and thin
primary structure consists of a repetitive sequence of amino acids
perform structural roles so they are strong and insoluble
less sensitive to changes
Nucleic acids
Polymers of nucleotides joined by phosphodiester bonds
made up of pentose sugar (ribose or deoxyribose), nitrogenous base, phosphate
