2.1.2 Biological molecules Flashcards
What chemical elements make up carbohydrates
Carbon
Hydrogen
Oxygen
What chemical elements make up lipids
Carbon
Hydrogen
Oxygen
What chemical elements make up proteins
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
What chemical elements make up nucleic acid
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Example of a hexose monosaccharide
glucose
Example of a pentose monosaccharide
ribose
deoxyribose
Draw an alpha glucose molecule
Draw a beta glucose molecule
Properties of monosaccharides
- sweet
- soluble
- forms crystals
- hydrophilic
Glucose + glucose
maltose
Glucose + fructose
sucrose
Glucose + galactose
lactose
What bond is formed from two monosaccharides
glycosidic bond formed by condensation polymerisation
Function / structure of starch
storage carbohydrate in plants
- made from alpha glucose
- insoluble
What is amylose
straight chains of glucose
(1 - 4) glycosidic bonds
What is amylopectin
branched starch
(1-4) and (1-6) glycosidic bonds
Function / structure of glycogen
storage carbohydrate in animals (muscles + liver)
- alpha glucose
heavily branched
(1-4) and (1-6) glycosidic bonds
Why is glycogen more suited to being an energy store than amylopectin
glycogen is more heavily branched
- so can be broken down into glucose much quicker for use in respiration
- also more compact so less space needed for storage
Function / structure of cellulose
structural polysaccharides in plants
- beta glucose
- no branching
- forms microfibrils
Give three properties of cellulose
- high tensile strength
- inflexible
- insoluble in water
How is cellulose bonded
every other beta glucose is inverted to form glycosidic bonds between the hydroxyl groups
What groups do amino acids have
- amine group
- carboxylic group
- r group
Draw an amino acid
What bond forms between amino acids
peptide bond
formed through a condensation reaction
What are prosthetic groups
non protein parts in proteins
e.g iron in haemoglobin
Properties of globular proteins
compact globe structure
hydrophobic R-groups face inwards and hydrophilic R- groups on the outside
- makes them soluble in water
Properties of fibrous proteins
form fibres
regular repetitive sequences of amino acids
usually insoluble
What is the primary structure of a protein
the sequence of amino acids held together by peptide bonds
What is the secondary structure of a protein
polypeptides which are either folded to form a beta pleated sheet
or twisted to form an alpha helix
shape is maintained by hydrogen bonds
What is the tertiary structure of a protein
a complex 3d shape achieved by twisting and folding
R-groups can form bonds with other R-groups
- ionic
- covalent
- disulfide
- hydrogen bonds
- hydrophilic / hydrophobic interaction
What is the quaternary structure of a protein
when a protein is made of more than one polypeptide subunit (unusual)
- haemoglobin and antibodies (4 polypeptides)
- collagen (3 polypeptides)
What is a lipid
a chemical that dissolves in organic solvents such as alcohol, but not in water (insoluble)
macromolecules - not polymers
- triglycerides
- phospholipids
- steroids
What is a triglyceride made of
one molecule of glycerol and 3 fatty acids
What is the difference between a saturated fatty acid and an unsaturated fatty acid tail
an unsaturated fatty acid has a double carbon bond
Uses of triglycerides
- source of energy in respiration
- thermal insulation
- buoyancy
How do triglycerides bond
the hydroxyl group of the glycerol reacts with the carboxylic acid group of the fatty acid to form an ester bond through a condensation reaction
What is a phospholipid made of
a phosphate group
glycerol
two fatty acid tails
- even number of carbon atoms each (16 or 18), one saturated and one unsaturated
How does the composition of the phospholipid contribute to the fluidity of the cell membrane
mainly saturated FA tails - membrane will be less fluid
mainly unsaturated FA tails - membrane will be more fluid
What is the structure of a steroid hormone (cholesterol etc)
4 carbon-based ring structures
hydroxyl group at one end (polar and hydrophilic)
rest of the molecule is nonpolar and hydrophobic
What are the main functions of cholesterol
- makes up steroid hormones and vitamin D
- prevents phospholipids solidifying at low temps and being to fluid at high temps
- gives mechanical stability as it restricts the movements of the phospholipids (decreases fluidity)
Properties of water
- universal solvent as it is polar
- liquid
- cohesion
- freezing
- thermal stability (high specific heat capacity)
What is the importance of water being a liquid at room temperature
acts as a liquid transport medium
- blood in animals
- used in plant transport systems
What is the importance of water being cohesive
gives water high surface tension - used by small organisms as habitat
used in xylem to make a transpiration stream
What is the importance of water being thermally stable
oceans provide a stable habitat for animals (requires huge amounts of energy to increase the temperature)
evaporation is used by many land based organisms as a cooling mechanism
Why is water considered to be a polar molecule
electrons in water are not shared evenly
molecule becomes slightly negatively charged at the oxygen end and slightly positively charged at the hydrogen end
Functions of hydrogen ions
H+
- hydrogen bonding
- control of blood pH
- opening stomata (proton pump)
- transported out of companion cells to return with sucrose through co transporter proteins
Functions of calcium ions
Ca2+
- bone and enamel structure (calcium phosphate)
- cofactor for enzymes
- synaptic transmission of nerve impulses
- muscle contraction
Function of iron ions
Fe2+ / Fe3+
- transport of oxygen via haemoglobin
- transfer of electrons (respiration and photosynthesis)
Function of sodium ions
Na+
- generating nerve impulses
- reabsorption of water in the kidneys
- co transporter of glucose and amino acids
Function of potassium ions
K+
- generating nerve impulses
- reabsorption of water in the kidneys
- opening of the stomata
- regulating fluid balance
Function of ammonium ions
NH4+
- deamination of proteins
Function of nitrate ions
NO3-
- source of nitrogen for plants
Function of hydrogen carbonate ions
HCO3-
- carbon dioxide transport in the blood
Function of chloride ions
Cl-
- maintaining pH balance during carbon dioxide transport
- cofactor for amylase enzyme
Function of phosphate ions
PO43-
- components of the cell membrane (phospholipids)
- component of bone (calcium phosphate)
- component of ATP and nucleic acids
Function of hydroxide ions
OH-
- determines pH
