Biological Molecules Flashcards
What are the 3 main functions of carbohydrates?
- Storage of energy
- Release of energy
- Cellular structures (cellulose cell wall of plant cells)
Why is glucose called a hexose sugar?
Monosaccharide that contains 6 carbon atoms
What’s the difference between alpha and beta glucose?
ABBA (OH group)
Alpha Below
Beta Above
What is an isomer?
Molecules with the same chemical formula but different arrangements of their atoms
What are the 2 other hexose sugars?
Fructose and galactose
What is a property of monosaccharides?
Soluble in water
Due to small size so easily dissolve in cell and are easily transported in the bloodstream
Alpha glucose + alpha glucose =
Maltose
Glucose + fructose =
Sucrose
Glucose + galactose =
Lactose
What’s the name of the bond between the 2 sugars in a disaccharide?
Glycosidic
How can disaccharides be broken back down to monosaccharides?
Hydrolysis reaction
(Breaking of the glycosidic bond by chemically inserting water)
Properties of polysaccharides eg starch (ICE)
- INSOLUBLE so don’t affect osmosis
- COMPACT so can be stored in small placed in the cell/can store a lot in one area
- EASILY HYDROLYSED to release the glucose for respiration
Give 4 examples of polysaccharides
- STARCH (storage in plants)
- GLYCOGEN (storage in animals)
- CELLULOSE (structural in plants)
- CHITIN (structural in animals)
Are storage polysaccharides alpha or beta glucose?
Alpha
Are structural polysaccharides alpha or beta glucose?
Beta
(Beat it and it will keep its shape)
What 2 molecules make up starch?
Amylose and amylopectin
Describe the structure of amylose
Straight chained, helical polymer containing alpha 1-4 glycosidic bonds
Describe the structure of amylopectin
Branched polymer containing alpha 1-4 and alpha 1-6 glycosidic bonds
Where is glycogen stored?
Liver and muscle cells
Describe the structure of glycogen
Highly branched polymer containing alpha 1-4 and alpha 1-6 glycosidic bonds
Describe the structure of cellulose
- Beta glucose monomers joined by 1-4 glycosidic bonds
- Each adjacent beta glucose monomer rotated 180
- Forming straight chains
- Hydrogen bonds form between OH groups of straight chains
- Many straight chains joined together by many hydrogen bonds forms a strong microfibril
What are the properties of chitin?
- lightweight
- waterproof
- very strong
(Forms exoskeleton of arthropods eg insects)
What 2 components are triglycerides made up of?
Glycerol
Fatty acids
What is the name of the bond that links triglycerides and phospholipids?
Ester bond
What’s the formula of glycerol?
C3H8O3
H H H H - C - C - C - H OH OH OH
General structure of fatty acid
Carboxyl group (COOH)
Hydrocarbon chain (CH2)
Methyl group (CH3)
What’s the difference between a saturated and unsaturated fatty acid?
Saturated has no carbon to carbon double bonds whereas unsaturated has carbon to carbon double bonds
Draw condensation reaction that takes place during the formation of a triglyceride from glycerol and three fatty acids
Page 18 in BM booklet
What do low density lipoproteins do?
LDLs contain and transport saturated fats and cause harm. Fatty material can block major arteries and cause a heat attack.
What do high density lipoproteins do?
HDLs contain and transport unsaturated fats and carry harmful fats away to liver for disposal. Higher proportion of HDL in blood lowers the risk of heart disease.
What are 3 properties of lipids?
> INSOLUBLE in water but soluble in organic solvents eg ethanol
Fats are solid at room temp eg butter
Oils are liquid at room temp eg olive oil
State the 6 functions of lipids
> Energy storage
Protection of vital organs from impact
Thermal insulation
Buoyancy
Metabolic water
Waterproofing (cuticle of plant, exoskeleton of insects)
What is the structure of a phospholipid?
A glycerol, two fatty acids and a phosphate group
Which part of the phospholipid is hydrophilic?
Polar head group.
The fatty acid tails are hydrophobic.
What are phospholipids an important component of?
Cell membranes
What are the 3 groups in an amino acid?
Amino group (H2N), variable ‘R’ group, carboxyl group (COOH)
There are 20 amino acids found in nature. How to they differ from each other?
Different variable groups
Draw a diagram to illustrate the condensation reaction that takes place during the formation of a dipeptide from 2 amino acid monomers
Page 23 of NB
What is the bond between 2 amino acid monomers in a dipeptide called?
Peptide bond
What is the primary structure of a protein?
The number and sequence of amino acids in a polypeptide chain
What is the secondary structure of a protein?
The primary structure of the polypeptide coils to form either an alpha-helix or a beta-pleated sheet.
Most common is alpha-helix which is held in spiral shape by HYDROGEN bonds.
Beta-pleated sheet (flat zigzag structure) also stabilised by hydrogen bonds.
What is the tertiary structure of a protein?
(And how they’re held in place)
Where the secondary structure folds to give complex 3D shapes.
Held in shape by bonds or interactions that form between R groups of some amino acids in the polypeptide chain.
What bonds hold together the tertiary structure of a protein?
- Hydrogen (form between O and OH)
- Ionic bonds (between oppositely charged R groups)
- Disulphide bridges (between S atoms)
- Hydrophobic interactions (on inside of the protein)
- Hydrophilic interactions (on outside of protein)
What is the quaternary structure of a protein?
When more than one polypeptide chain each with a tertiary structure combine. Sometimes associated with non-protein groups called prosthetic groups. Eg haemoglobin
What are the 2 classifications of proteins?
Fibrous proteins and globular proteins
What makes fibrous proteins effective at carrying out STRUCTURAL functions?
- Tough
- Non-specific
- Insoluble
What are the properties of globular proteins?
- Compact and folded into spherical molecules
- Have a specific shape
- Soluble in water
How do you test for proteins?
- Add a few drops of biuret reagent to protein solution
- Shake gently
- Blue —> purple
How do you test for reducing sugars eg glucose?
- Add a few drops of Benedict’s reagent to test sample
- Heat in water bath
- Blue —> brick red
May be graduated between green, yellow orange or brick-red
Semi-quantitative
How do you test for non-reducing sugars?
If negative result was found initially with Benedict’s and boil test:
- Add HCl to test sample and heat in water bath (hydrolyse any glycosidic bonds)
- Add bicarbonate of soda to neutralise
- Add Benedict’s reagent and heat in water bath
- Blue —> brick red
How do you test for starch?
- Add a few drops of iodine solution
- Orange —> blue/black
How do you test for lipids?
- Mix test sample with an equal volume of ethanol
- Add mixture to an equal volume of water and shake
- Cloudy white emulsion will form
What is cohesion?
Water molecules sticking together as a result of the formation of hydrogen bonds
What are the 7 properties of water?
- Surface tension
- Universal solvent (excellent transport medium)
- Metabolite
- High specific heat capacity
- High latent heat capacity
- Density
- Transparency