2.1.2 Biological molecules Flashcards
what are the different biological molecules
carbohydrates
lipids
proteins
nucleic acids
what is a monomer
smaller units that combine to make a large molecule (polymer)
what is a polymer
large moecules made up of many repeating units of monomer joined together by chemical bonds
what is polymeriation
the process where monomers join to form polymers
when is a condensation reaction
the removal of water to form a chemical bond between two molecules
what is a hydrolysis reaction
the addition of water to break a chemical bond between two molecules
how is water bonded
- it is bonded covalently
- it is a polar molecule
- oxygen has more protons and attracts the shared pair of electrons closer to it, this makes the oxygen slightly electron negative and the hydrogen slightly electron positive
- the bond is between molecules and is weak
how can water molecules form hydrogen bonds
- the partially negative oxygen of one molecule will be attracted to a slightly positive hydrogen of another water molecule.
- this causes the water molecules to become attracted toward each other which is known as hydrogen bond
- this causes the water molecules to stick together
what are some properties of water
- solvent - many substances can dissolve in water
- coolant mechanism
-temperature buffer - transport medium/ cohesion and adhesion
- habitat ( density and surface tension)
describe how water can be used as a solvent
- water is a universal solvent
- the slightly negative o will attract the positive element and the slightly positive H will attract the negative element in an ionic compound.
- this causes the ionic compound to split apart in water.
- this is important as cells are mostly water, and many substances within cells are ionic compounds.
- this allows for reactions to occur more frequently, which allows organisms to respond to its environment
- this also allows dissolved substance to be transported around the body, eg ions in the blood plasma
describe how water is used as a temperature buffer
- water has a high heat capacity
- the hydrogen bonds between water molecules can absorb a lagre amount of heat before changing states
- this stabilises temperatures of bodes of water so it provides a habitat for animals
- it also allows the body of organisms to remain at a fairly stable temperature
describe how water can be used as a coolant
- a lot of energy is needed to turn water into gas sue to a high heat capacity
- this is useful as organisms can use evaporation of water as a method of cooling without loosing too much water.
- when water evaporates from the surface of the skit it takes heat energy away, which cools down the organism
describe how water can be used as a habitat
- since water has a high heat capacity and a high latent heat of vaporisation, this means that water provides a stable environment for many organisms to live in
- at low temps when water freezes into ice, the ice will float as the water molecules are held further apart in ice, making it less dense
- this causes the ice to form an insulation layer at the surface of ponds and lakes, allowing for organisms under the ice to move and survive
- if water was less dens, animals would struggle to float to use as a habitat
what is cohesion and adhesion and how does this help water being a transport medium
cohesion - hydrogen bonds in water causes water molecules to stick together
adhesion - the ability to cling to other polar surfaces
- this is important as water fills internal transport system of plants and animals, and due to being cohesive and adhesive water allows for efficient transport of nutrients and waste
what are the chemical elements that make up carbohydrates
C, H, O
what are the chemical elements that make up lipids
C, H, O
what are the chemical elements that make up proteins
C, H, O, N, S
what are the chemical elements that make up nucleic acids
C, H, O, N, P
what are carbohydrates
a biological molecule containing the elements C,H,O
what are the roles of carbohydrates
- to supply energy for cells
- for sugars to be stored as complex carbohydrates
- to be used as structural components such as cellulose and chitin
- cell recognition - glycoproteins help cells identify each other and communicate
what are the three types of carbohydrates
- monosaccharide ( on monomer)
- disaccharide ( two monomers)
- polysaccharide ( many subunits)
what are examples of monosaccharides
- glucose
- fructose
- galactose
what are examples of disaccarides
- maltose
- sucrose
- lactose
what are examples of polysaccharides
- starch
- glycogen
- cellulose
what are monosaccharides
- the simplest form of carbohydrates known as simple sugars
what is the general formula for carbohydrates
(CH2O)n
n is any number between 3 to 7
what is a hexose monosaccharide
it is a monosaccharide that contains 6 carbon atoms
what is a pentose monosaccharide
it is a monosaccharide that contains 5 carbon atoms
what are examples of hexose monosaccharides
- Glucose
- Fructose
- Galactose
what are example of pentose monosaccharide
- Ribose
- Deoxyribose
what is a similarity between all monosaccharides
- they are all reducing sugars meaning it is able to reduce another compound and itself
what is the structure of
hexose monosaccharide: alpha glucose, beta glucose
pentose monosaccharide: ribose
refer to spec notes
what are some properties of glucose
- primary energy source for plants and animals
-its is soluble making it easy for glucose to be transported around organism - the bonds store lots of energy which is released when broken
- glucose is mainly used as energy for respiration
how are disaccharides formed
- when two monosaccharides join together through a condensation reaction
what are examples of two monosaccharides that turn into disaccharides
a glucose + a glucose = maltose
a glucose + galactose = lactose
b glucose + fructose = sucrose
this all forms water as it is a condensation reaction
describe how disaccharides are formed in a condensation reaction
- a hydroxyl group (OH) of one monosaccharide reacts with a hydroxyl group (OH) of another monosaccharide
- This forms a glycosidic bond, and a water molecule (H2O) is released
describe how disaccharides are broken down via hydrolysis reaction
- When a water molecule (H2O) is added to a disaccharide, the glycosidic bond is broken to release the 2 monosaccharides.
what is a polysaccharide
- complex carbohydrates made up of many monosaccharides joined via glycosidic bonds
what are some examples of polysaccharides
- starch
- glycogen
- cellulose
what is the use of starch
- used by plants to store excess glucose
what are the polymers of starch
amylose and amylopectin
describe the structure of amylose
- long, unbranched chain of alpha-glucose joined by 1-4 glycosidic bonds
- the angle of the bonds allows the chain to coil into a helix to make a compact structure
describe the structure of amylopectin
- long, branched chain of alpha-glucose joined by 1-4 and 1-6 glycosidic bonds
describe how the structure and properties starch relates to its function
- insoluble - it doesn’t affect the water potential, so water doesn’t enter cells by osmosis
- large - cannot diffuse out of cells
- many side branches (amylopectin) - the allows enzymes to hydrolyse the glycosidic bonds more quickly to release the glucose
- coiled ( amylose) - this makes it compact so lots of glucose can be stored in a small place
- hydrolysis will release alpha glucose monomer which are ready to use in respiration
what is the use of glycogen
used by animals to store excess glucose
describe the structure of glycogen
made up of many alpha - glucose monomers joined via 1-4 to 1-6 glycosidic bond to form highly branched chains
describe how the structure and properties glycogen relates to its function
- insoluble - it doesn’t effect the water potential of cell, so water doesn’t eater the cell via osmosis
- compact - lots of glucose can be stores in a small space
- very highly branched - can easily hydrolyse the glycosidic bonds to rapidly release glucose
- it cannot diffuse out of cells
- hydrolysis of glycogen will release alpha glucose which is ready to use for respiration
what is the function of cellulose
- mainly used as structural support for plant cell walls
describe the structure of cellulose
- many beta-glucose monomers joined together to form long, straight unbranched chains.
- every other beta-glucose molecule is flipped upside down to being the hydroxyl groups close enough to react to form hydrogen bonds
describe how the structure and properties cellulose relates to its function
- it has long straight and unbranched chains - to provide rigidity to the cell wall
- has hydrogen bonds - cross links the chains to add collective tensile strength
- cellulose forms microfibrils - which provides additional strength
what is the use of glucose
used as the primary energy source in animals and plants
describe the structure of glucose
- molecular formula C6H12O6
- hexane monosaccharide
- can be alpha glucose or beta glucose, refer to spec notes for the diagram
describe how the structure and properties glucose relates to its function
- it is soluble - so that it can be transported around the organism
- its bonds store lots of energy - energy is releases when the bonds are broken
what are lipids
- a biological molecule containing C,H,O
- not considered a polymer
- made up of fatty acids combined with an alcohol ( usually glycerol)
what are the roles of lipids
- energy supply - lipids can be oxidised to provide energy to cells
- structural components - phospholipids are used in cell membranes
- waterproofing - insoluble lipids are used to form water-resistant barriers
- insulation - can help to retain heat
- protection - protects delicate organs
what are fatty acids
they consist of a carboxyl group (-cooh) attached to a hydrocarbon chain ( r group)
What are the two types of fatty acids
saturated fatty acids and unsaturated fatty acids
what is the difference between saturated and unsaturated fatty acids
- saturated fatty acids have no carbon- carbon double bonds
- saturated fatty acids have a high melting point, and it solid at room temp
- unsaturated fatty acids have at least on carbon double bond
- unsaturated fatty acids are usually liquid at room temp.
what are the two types of unsaturated fatty acids
monounsaturated - one double bond
polyunsaturated - two or more double bonds
what are two examples of macromolecules
- triglycerides and phospholipids
what are triglycerides
a type of lipid used as a store of energy in animals, plants and some bacteria
describe the structure of a triglyceride
consists of a glycerol backbone attached to three fatty acid tails
refer to spec notes for diagram
explain how the structure and properties of a triglyceride relate to its function
- long hydrocarbon tails - many carbon-hydrogen bonds can be broken to release energy
- low mass to energy ratio - lots of energy can be stored in a small volume
- insoluble - they do not affect the water potential of cells as they are large and non-polar
- high ratio of hydrogen to oxygen atoms - will release water when oxidised
describe the synthesis of triglycerides
- triglycerides are synthesised via condensation reactions
- the hydroxyl group (OH) on the glycerol and on the three fatty acids will react together
- this releases three water molecules
- this forms three ester bonds between the glycerol and the fatty acids
describe the breakdown of triglycerides
- triglycerides are broken down via hydrolysis reactions
- three water molecules are added which breaks the ester bonds
- this separates the glycerol and fatty acids
what is a phospholipid
a type of lipid used as a structural component of the cell membrane
describe the structure of a phospholipid
- contains glycerol which has a phosphate group and two fatty acid tails attached to it
- phospholipids are polar
- has a hydrophilic head ( glycerol and phosphate)
and a hydrophobic tail ( contains fatty acid)
describe how the structure and properties of a phospholipid relate to its function
- forms a membrane bilayer, two rows of phospholipids , the heads pointing outward and the tails point inwards
- this arrangement creates a hydrophobic centre in the bilayer so that the water-soluble substances cannot pass through
what is cholesterol
- a type of lipid which is used by animal cells to increase the stability of the cell membrane
explain how the properties of cholesterol molecules relates to their functions
- cholesterol is a polar molecular
- it binds to phospholipid fatty acid tails causing the phospholipids to pack more closely together.
- this helps to reduce the fluidity of the cell membrane
what are proteins
large, complex molecules with unique 3d structure
what are proteins made of
- amino acids
what is a dipeptide
when two amino acids are joined together via peptide bonds
what is a polypeptide
when 3 more more amino acids are joined together via peptide bonds
what are the roles of proteins
- enzymes - there are used for the breakdown and synthesis of molecules
- antibodies - molecules involved in immune response
- transport - some proteins can move molecules or ions across membranes
- structural components - proteins like keratin and collagen used to create strong fibres
- hormones - some hormones are proteins which cat as chemical messengers in the body
- muscle contraction - muscles are made up of proteins
describe the structure of an amino acid
- a central carbon atom
- an amino group -NH2
- a carboxyl group - COOH
- a hydrogen atom
- an R group
REFER to spec notes for diagram
how many amino acids are there
- there are 20 different amino acids
- each amino acid has a different R group which determines its properties
explain the synthesis of dipeptides and polypeptides
- synthesised via condensation reactions
- the hydroxyl (OH) in the carboxyl group of one amino acid reacts with the hydrogen (H) in the amino group of another amino acid.
- this releases a water molecule
- this forms peptide bonds between the carbon of one amino acid and the nitrogen of another
explain the break down of dipeptides and polypeptides
- breakdown via hydrolysis
- the water molecule is added, which breaks the peptide bond
- in a dipeptide the two amino acids will seperate
what are proteins 4 structures
- primary
- secondary
- tertiary
- quaternary
describe and explain the primary structure of proteins
- made up of a unique sequence of amino acids held in a polypeptide chain
- this structure is held by peptide bonds
- a change to one of the amino acids can result in a change to the proteins structure and function
describe and explain the secondary structure of proteins
- hydrogen bonds forms between the amino group of one amino acids and the carboxyl group of another amino acid further down the chain
- this causes the polypeptide chain to coil into an alpha-helix or a beta-pleated sheet structure
describe and explain the tertiary structure of proteins
-the tertiary structure forms when the polypeptide chain folds and twist further to create a complex 3d structure.
- this structure is held together by:
1. hydrogen bonds - strong in large number/ lots of bonds
2. ionic bonds - these form between positive and negative R groups
3. disulphide bridges - these form between R groups that contain sulphur
3. hydrophobic and hydrophilic interactions - these weak interaction between polar and non-polar R groups
describe and explain the quaternary structure of proteins
- two or more polypeptide chains held together by the same bonds as the tertiary structure
- the quaternary structure can also include the addition of non-protein group known as prosthetic groups
- only some proteins have a quaternary structure
what are the two types of proteins
- globular
- fibrous
what is a conjugated protein
a globular protein with a prosthetic group
what is the structure of globular proteins
Globular proteins are compact, spherical, and soluble proteins.
what are some examples of globular proteins
- they tend to have metabolic roles in the body
enzyme - speed up chemical reaction
hormones - chemical messenger in the bloodstream
antibodies - bind to and prevent spread of pathogen
what is the function of haemoglobin
( globular) ( conjugated protein)
- used to carry oxygen around the body in red blood cells
- haemoglobin is a conjugated protein as it contain a prosthetic group, iron.
1. contains 4 polypeptide chain to carry 4 molecules of oxygen
2. haem group - contains iron that reversibly binds to oxygen
3 - compact globular structure - allows haemoglobin to fit inside the red blood cells
what is the function of insulin (globular)
- it is a hormone used to regulate blood glucose concentration
-travels through the blood stream so needs to be soluble - needs a specific shape to fit with receptors on cell - surface membrane
- made up of two polypeptide chains held by bisulfide bonds
what is the function of amylase (globular)
- It is an enzyme responsible for the breakdown of starch into maltose
- the enzyme is made up of single polypeptide chain folded using both alpha - helix and beta-pleated sheets
what is the structure of fibrous proteins
- long strands
- insoluble in water
- strong and thin
what are some example of fibrous proteins
tend to have structural roles
- keratin
- collagen
- elastin
what is the function of collagen
- used as a structural component in skin, tendons, cartilage, bones, teeth and walls of blood vessels
- made of three polypeptide chains wound around each other in a rope-like structure.
- this provides strength and flexibly to the molecule
what is the function of keratin
- found in hair, skin and nails
- has disulfide bonds which creates strong and insoluble molecules
- keratin can be flexible or rigid depending on the number of bisulfide bonds it contains
what is the function of elastin
- a fibrous protein found in elastic connective tissue such as in the walls of blood vessels
- it is elastic which allows the tissues to expand and then return to their original shape
describe the test for proteins/biuret test
- Place your food sample in a test tube.
- Add an equal volume of Biuret solution (sodium hydroxide and copper sulfate).
- If proteins are present, the solution will turn from blue to purple. If no protein is present, the solution remains blue.
describe the benedict’s test for reducing sugars
- Place 2 cm3 of your food sample into a test tube.
- Add an equal volume of Benedict’s reagent.
- Heat the mixture in a gently boiling water bath for 5 minutes.
- If a reducing sugar is present, the mixture will change from a blue solution to a brick red precipitate.
Blue - This indicates no reducing sugar is present.
Green - This indicates a low concentration.
Orange - This indicates a medium concentration.
Brick-red - This indicates a high concentration.
what is a quantitative method to determine the concentration of reducing sugars
Use a colorimeter to measure the absorbance of each solution
OR
Filter the solution and weigh the precipitate.
describe the benedict’s test for non-reducing sugars
- Carry out the test for reducing sugars, and if the result is negative (turns blue), continue with the next steps.
- Add 2 cm3 of the food sample to 2 cm3 of dilute hydrochloric acid.
- Heat the mixture in a gently boiling water bath for 5 minutes (the acid will hydrolyse disaccharides into monosaccharides).
- Neutralise the mixture by adding sodium hydrogen carbonate solution.
- Retest this mixture using the test for reducing sugars.
- If non-reducing sugars were present at the start, the mixture will now change from a blue solution to a brick red precipitate.
describe the iodine test for starch
- Place 2 cm3 of your food sample into a test tube.
- Add a couple of drops of iodine solution and shake.
- If starch is present, the solution will turn from orange to blue-black.
describe the emulsion test for lipids
- Place your food sample in a test tube.
- Add 2 cm3 of ethanol.
- Shake.
- Add 2 cm3 of distilled water.
- If lipids are present, a milky white emulsion will appear.
