Biological Molecules Flashcards
What are biological molecules?
Groups of chemicals found in living organisms
What are the 3 most common bonds in biology?
Covalent bonding
Ionic bonding
Hydrogen bonding
What is a covalent bond?
Atoms share a pair of electrons in their outer shell forming molecules
What is ionic bonding?
Electrostatic attraction between two ions
What is hydrogen bonding?
Weak electrostatic bonds between a negative region of a polarised molecule and positively charged region
What is a monomer?
A small molecule that combines with other small molecules to form a larger molecule called a polymer
What is a polymer?
A large molecule made up of repeating smaller molecules called monomers
What is the process of joining monomers to make a polymer called?
Polymerisation
What element are monomers usually based on?
Carbon
What is condensation?
A chemical process where two molecules combine to form a more complex molecule often creating water
What is hydrolysis?
The breaking down of large molecules into smaller molecules by the addition of water
What is metabolism?
The chemical process that take place in living organisms
What is a monosaccharide?
A sweet tasting carbohydrate
What is the formula for monosaccharides?
(CH20)n where n iOS any number from 3 to 7
List the 3 monosaccharides
Glucose (a and b)
Fructose
Galactose
What is the difference between alpha glucose and beta glucose?
Aloha has a hydrogen atom next to oxygen
Beta has OH next to the oxygen atom
What is a reducing sugar?
A monosaccharide (and some disaccharides such as maltose) that can reduce another chemical
What is the test for a reducing sugar?
Benedicts Test
What is Benedicts reagent?
An alkaline solution of copper (II)sulphate
How do you carry out the Benedicts test?
Add Benedicts reagent to a substance and heat
What are the results for the Benedicts test?
Brick red signals high amounts of reducing sugars
remains blue: no reducing sugars are present
What is a disaccharide?
A pair of monosaccharides chemically bonded by a glycosidic bond
What is a glycosidic bond?
The carbon-oxygen-carbon bond between two monosaccharide molecules
Alpha glucose + Alpha glucose =
Maltose
Maltose is broken down by
Maltase
Alpha glucose + fructose =
Sucrose
Sucrose is broken down by
Sucrase
Alpha glucose + galactose =
Lactose
Lactose is broken down by
Lactase
List three disaccharides
Maltose
Sucrose
Lactose
What is the test for non-reducing sugars?
Hydrolyse the reducing sugar into its monosaccharides
Add Benedicts reagent and heat
What is a polysaccharide?
A polymer chain of many monosaccharide molecules joined by glycosidic bonds
What are the common features of a polysaccharide?
Large molecules
Insoluble
Good for storage
Can be hydrolysed into disaccharides and monosaccharides
What is the test for starch?
Add potassium iodide solution (iodine solution)
Shake or stir
What are the results for the test for starch?
Blue-Black starch is present
What is starch?
A polysaccharide found in plants in the form of small fm grains
What is starch made up from?
200-100,000 alpha glucose monosaccharides
What is amylose?
An unbranched coiled chain of starch
What is amylopectin?
A long branched chain of starch
What is the main role of starch?
Energy storage
How is starch suited for its function?
It’s insoluble and doesn’t affect water potential
Large so it doesn’t diffuse out of cells
Compact so it can be stored in small space
Produces a glucose when hydrolysis E for easy transportation and respiration
Branched can be catalysed rapidly
What is glycogen?
A polysaccharide found in animal cells stored as small granules
What is the function of glycogen?
Major carbohydrate storage for animals (particularly in the liver)
How does the structure of glycogen make it suitable for its job?
Insoluble doesn’t affect water potential
Insoluble so doesn’t diffuse out of cells
Compact can be stored in small space
More branches broken down rapidly into glucose for respiration
Why is rapid glucose production more important to animals than plants?
It is used in respiration
Animals have a higher metabolic rate
Therefore a higher respiratory rate as they are more active
What is cellulose made from?
Alpha glucose monosaccharides
What is cellulose?
A polysaccharide found in fibre like strands
What is cellulose made from?
Beta glucose monosaccharides
Describe the structure of cellulose
Straight unbranched chains running parallel to one another allowing hydrogen bonds between chains
Grouped together to form microfibres which group together to form fibres
What is the function of cellulose?
Provides rigidity to plant cell walls
Prevents cells bursting from oso modus by exerting inward pressure
Keep non-woody parts of plants turgid
How is cellulose adapted to its function?
Hydrogen bonds forming cross links between chains gives collective strength
Microfibres turn into fibres providing more strength
What is a lipid?
Insoluble fats that provide energy, insulation and protections for organisms
What properties do lipids have?
Carbon hydrogen oxygen based (in smaller amounts than carbohydrates)
Insoluble in water
Soluble in organic solvents (eg alcohol and acetone)
What are the main lipid groups?
Triglycerides and phospholipid
What is the role of lipids in cell membranes (cell-surface and around organelles?)
Phospholipids contribute to flexibility and transfer of lipid so liable substances
What are the roles of lipids?
Energy source
Waterproofing
Insulation
Protection
How do lipids work as a source of energy?
Provide water and more than twice as much energy than carbohydrates when oxidised
How do lipids work as waterproofing?
Insoluble in water
Plants and insects have waxy lipid cuticles that conserve water
Mammals produce an oily secretion from sebaceous glands in the skin
How do lipids provide insulation?
Fats are slow conductors of heat and help retain body heat when stored beneath the surface of the body
Act as electrical insulators as the myelin sheath in nerve cells
How do lipids act as protection?
Fat is stored around delicate organs such as the kidney and heart
What are the differences between fats and oils?
Fats : saturated fatty acids, solid at room temperature (10-20C)
Oils: unsaturated fatty acids, liquid at room temperature (10-20C)
What is a triglyceride?
Glycerol and three fatty acids
What is an ester bond?
The bond that forms between H and HO in glycerol and fatty acids
What causes different properties in fats and oils?
The combinations and variations of fatty acids
How many fatty acids are there?
Over 70
What structure do all fatty acids have?
A carboxyl group with a hydrocarbon chain
What is a saturated fatty acid?
A hydrocarbon chain with no carbon-carbon double bonds
What is a monounsaturated fatty acid?
A hydrocarbon chain with one carbon-carbon double bond
What is a polyunsaturated fatty acid?
A hydrocarbon chain with more than one carbon-carbon double bond
Why are triglycerides a good energy source?
High ratio of energy storing carbon-hydrogen bonds to carbon atoms
Low mass to energy ratio- more energy stored in small volume
Insoluble so no affect on water potential and osmosis in cells
Provide water when oxidised
What are phospholipids?
Similar to a lipid it has fatty acid tails however has a phosphate molecule
What is an important feature of phospholipids?
Polar molecule / solvable
Fatty acids are hyrophobic
Phosphate molecule is hydrophilic
What does hydrophilic mean?
Interacts with water but not fat
What does hydrophobic mean?
Interacts with fat but not water
Which parts of the phospholipids are hydrophobic and which are hydrophilic?
Head - hydrophilic
Tail - hydrophobic
How does phospholipids being bipolar relate to its function?
Forms a bilateral within cell surface membranes Forming a hydrophobic barrier between the inside and outside of a cell
Help hold the surface of the cell membrane
Allows formation of glycolipids important for cell recognition
What is the test for lipids?
The emulsion test
How do you carry out an emulsion test?
Add ethanol
Shake thoroughly to dissolve any lipids in the sample
What are the results of an emulsion test?
Cloudy - lipid present
Clear - no lipid present
What is a protein?
A very large molecule important in living organisms that differs greatly from organism to organism
What is an amino acid?
A monomer unit that combines with other amino acids to form dipeptides and polypeptides
How many amino acids are there?
About 100
20 of which naturally occur in proteins
What is the structure of an amino acid?
An amine group
A carboxyl group
A hydrogen atom
A functional group
What is a dipeptide?
Two amino acid monomers joined by a condensation reaction and a peptide bond
What is a peptide bond?
A bond between a carbon and nitrogen atom involving the formation of water
What is the primary structure of a protein?
A polypeptide chain formed by polymerisation
What is polymerisation?
When many amino acids condense to form a polypeptide chain
How is the primary structure of a protein formed?
The sequence of amino acids determined by DNA
What is the importance of the primary structure of a protein?
It determines the final shape of a protein and hence its function
A proteins function depends on its…
Shape
What is the secondary structure of a protein?
Alpha helix
Beta pleated sheets
How does the secondary structure of a protein form?
Hydrogen bonds form between H+ and O- in different amino acids
This causes the polypeptide to bend or coil
What is the tertiary structure of a protein?
Further 3D structures develop due to more twisting and folding
What bonds are found in the tertiary structure of proteins?
Disulphide bridges
Ionic bonds
Hydrogen bonds
What causes the bonds to occur in specific places in a protein?
The primary structure / amino acid sequence
Why is the 3D shape of a protein important?
It makes each protein distinctive
Allows it to interact with other molecules due to its shape
What is the quaternary structure of proteins?
More than one polypeptide chain bonded together
What may the quaternary structure of a protein have that no other structure has?
A prosthetic group (eg. Haem)
What is the test for proteins?
Biuret test
What is the biuret test?
Add biuret (copper sulphate solution) reagent to the sample
What is the result of a biuret test?
Purple - Protein present
Blue - No protein present
What are the two basic types of protein?
Globular
Fibrous
What is a fibrous protein?
A protein with structural function
What are the properties of fibrous proteins?
Long polypeptide chains that run parallel linked by cross-bridges
Give an example of a fibrous protein
Collagen
Keratin
What is a globular protein?
A protein carrying out metabolic functions
Give an example of a globular protein?
Enzymes
Haemoglobin
