Unit 2.2- Biological molecules Flashcards
Why is water important for life?
- Essential for photosynthesis
- Transporting molecules
- Maintaining shape
- Regulating temperature
What types of bonds are in water molecules?
Covalent (share electrons, strong bond)
What are the charges in a water molecule?
Hydrogen atoms are delta positive and oxygen is delta negative.
What are hydrogen bonds?
The small bonds between molecules formed by the slight charges of each atom.
Why is water hard to heat up?
Hydrogen bonds keep the molecules together and it takes a lot of energy to over come these bonds so additional heat energy is then needed to heat up the water.
What is specific heat capacity?
The amount of heat energy required to increase the temperature of 1 Kg of a substance by 1K.
What is latent heat?
The heat energy needed for a substance to change state without changing temperature.
What is surface tension:
Water molecules stick together. Molecules on the surface can only stick to molecules below them. This forms a strong layer on which small animals can walk.
What are carbohydrates?
Organic compounds which comprise of only carbon, hydrogen and oxygen.
What are the three types of carbohydrates?
- Monosaccharides
- Disaccharides
- Polysaccharides.
What are the properties of Monosaccharides?
- Simplest sugars
- Same number of carbon and oxygen
- Have the general formula CnH2nOn
- White crystalline solids
- Dissolve in water to form sweet tasting solutions.
What are the two forms of glucose?
Alpha glucose and beta glucose.
What do alpha and beta glucose form?
Alpha forms starch and beta forms cellulose.
What is an isomer?
When two compounds have the same molecular formula but different structural formula.
How are disaccharides formed?
By two monosaccharides joining together.
What type of reaction is it when a disaccharide is made?
A condensation reaction.
What is a condensation reaction?
When water comes out of the reaction.
What is a glycosidic bond?
The bond formed when disaccharides are formed.
How do you turn disaccharides back into monosaccharides?
Add water.
What type of reaction is it when you turn disaccharides back into monosaccharides?
Hydrolysis reaction.
What are the properties of disaccharides?
-Dissolve in water and taste sweet
What do two glucose molecules join together to make?
Maltose.
What are some examples of disaccharides and the monosaccharides they come from?
- Sucrose = glucose + fructose
- Lactose = glucose + galactose
- Maltose = glucose + glucose.
What are some examples of polysaccharides?
- Starch
- Cellulose
- Glycogen.
What is the function of starch and glycogen?
They are stores of energy.
What is the function of cellulose?
It is a structural unit.
What is the structure of starch like?
- Spiralling chains
- Molecules are all the same way up
- Amylose doesn’t branch
- Amylopectin branches.
What is the structure of cellulose like?
- Every second molecule is rotated by 180 degrees.
- This is the beta 1-4 glycosidic bonds help to prevent the chain from spiralling
- The hydroxyl group on carbon 2 sticks out, enabling hydrogen bonds to be formed between chains.
What is the structure of glycogen like?
- Lots of branches so little tendency to coil
- Compact
- Easier to remove monomer units (than from starch), as there are more ends.
What breaks down glycogen?
Amylase breaks it down through hydrolysis into glucose when required for respiration.
What type of starch branches?
Amalopectin
What type of starch doesn’t branch?
Amylose
What type of food are polysaccharides?
Carbohydrates
What is starch made up of?
A mixture of amylose and amylopectin or just one of them.
What is the main form of carbohydrate used for energy storage in animals?
Glycogen
Where is glycogen stored?
The muscles and the liver
In times of high energy use, what happens to glycogen?
The organs hydrolyse the glycogen stored and break i down into glucose molecules which can be used in respiration.
What is glycogen soluble in?
Water
Why is glycogen’s compact shape beneficial?
It makes it optimal for energy storage.
Microfibril definition:
Polymers of about 10,000 beta glucose molecules in a long unbranched chain.
What do microfibrils make up?
Macrofibrils
What group of lipids are fats and oils in?
Triglycerides
What are the properties of fats?
- Solid at room temperature
- More saturated
- C-C bonds
What are the properties of oils?
- Liquid at room temperature
- More unsaturated
- Some C=C bonds
What are triglycerides made up of?
1 glycerol and 3 fatty acid chains
What are triglycerides? (Not polymers)
Macromolecules
What type of reaction are Triglycerides formed in?
- Condensation reaction
- Forms an ester bond between glycerol and each FA chain.
- It is also known as esterification
What are ester bonds broken down by?
Hydrolysis
What type of bonds do unsaturated FAs contain?
1 or more C=C bond. It could bond to more H atoms.
What type of bonds do saturated FAs contain?
No C=C bonds. Cannot bond to any more H atoms.
What are the uses of lipids?
- energy store
- thermal insulator
- buoyancy
- protection of vital organs
What is the structure of a phospholipid?
Hydrophillic head and 2 hydrophobic tails
Why are unsaturated fatty acid tails in a phosopholipid bad?
It causes kinks and upsets the plasma membrane and causes it to be weaker.
What do phospholipids make up?
The plasma membrane of cells
What is the structure of phospholipids in a cell membrane?
They form a bilayer with the FA chains facing into each other because they are hydrophobic and the heads are hydrophillic. The polar heads dissolve in the aqueous intra and extracellular fluids.
Why are phospholipids suitable for forming cell membranes?
They enable integration of other molecules into the ‘mosaic’ and help to regulate the movement of molecules in and out of the cell.
What are the functions of proteins?
Growth and repair
What are some examples of proteins?
- Haemoglobin
- Antibodies
- Enzymes
- Hormones
- Signal receptors
- Collagen
What are essential amino acids?
Amino acids that ca’t be synthesised by the human body. We must get them from food.
Polypeptide chain definition:
A short chain of amino acids.
What is the structure of an amino acid?
H H O (double bond)
N C C
H R OH
What is the basic amino group of an amino acid?
NH2. On the left hand side.
What is the carboxyl (acidic) group of an amino acid?
COOH. On the right hand side.
What is the central group of an amino acid?
C-H. The middle and top.
What is the R-Group on an amino acid?
An additional chain, covalently bonded- this is different for each amino acid.
What type of reaction are two amino acids bound in?
Condensation.
What type of bond is formed when two amino acids bond?
Dipeptide bond.
What are the chemical elements in lipids?
- Carbon
- Hydrogen
- Oxygen
What are the chemical elements in nucleic acids?
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Phosphorus
What type of monosacharide is glucose?
Hexose (contains 6 carbons)
What type of monosacharide in ribose?
Pentose (contains 5 carbons)
What is the difference in structure between alpha and beta glucose?
Alpha glucose is H on top of OH
Beta glucose is OH on top of H
What structures are in the hydrophilic head of phospholipids?
- Phosphate group
- Glycerol group
What is the primary structure of an amino acid like?
- Specific sequence of amino acids in a polypeptide
- unique to each gene
What is the secondary structure of an amino acid like?
- Polypeptide coils or folds in on itself because of the interactions of individual amino acids (hydrogen bonds)
- This causes it to either form an alpha helix (strong) or a beta pleated sheet (weak)
What is the tertiary structure of an amino acid like?
- Alpha helix or beta pleated sheet folds in on itself
- 3D shape which often improves solubility due to interactions between R groups and involves ionic, disulphide and hydrogen bonds and hydrophilic and hydrophobic interactions
What is the quaternary structure of an amino acid like?
Interaction between two or more polypeptides, therefore only exists in proteins consisting of two or more polypeptides
What is the structure of haemoglobin?
- Quaternary structure
- Globular
- 4 polypeptide chains, 2 alpha, 2 beta
What is the structure of collagen?
- Quaternary structure
- Fibrous
What are the properties of globular proteins?
- Rolls up to form balls
- Soluble in water because hydrophobic R groups turn inwards and hydrophilic R groups turn outwards
- Usually have metabolic roles
- e.g. haemoglobin, insulin, antibodies.
What are the properties of fibrous proteins?
- Form fibres. Regular, repetitive sequence of amino acids
- Usually insoluble
- Usually have structural roles
- e.g. collagen, keratin.
What is the prosthetic group of haemoglobin?
Haem group
What is a conjugated protein?
A protein with an attached prosthetic group
What are examples of cations?
- Calcium ions (Ca2+)
- Sodium ions (Na+)
- Potassium ions (K+)
- Hydrogen ions (H+)
- Ammonium ions (NH4+)
What are examples of anions?
- Nitrate (NO3-)
- Hydrogen carbonate (HCO3-)
- Chloride (Cl-)
- Phosphate (PO4-)
- Hydroxide (OH-)
How does the Biuret test work?
- For proteins
- Biuret reagent (copper sulphate (III)? and potassium hydroxide) is blue
- The reagent turns purple in the presence of peptide bonds, indicating the presence of a protein.
How does the Benedicts test work?
- For reducing an non-reducing sugars
- For reducing sugars:
- Add Benedict’s reagent (Copper (II) suplhate in alkaline solution) to the sample
- Heat ina water bath at 80K for 3 minutes
- If there is reducing sugar, Cu2+ ions are reduced to Cu+ and the mixture is oxidisedand becomes brick red.
- For non-reducing sugars:
- Heat solution with acid to hydrolise any glycosidic bonds then neutralise solution with sodium hydroxide
- Then do the same method as for reducing sugars
How does the iodine test work?
- Tests for starch
- Uses potassium iodide as a source of iodine
- If starch is present, the solution will turn a dark blue-black colour. This is because iodine becomes trapped in the coils of starch.
How does the emulsion test work?
- Tests for lipids
- Shake sample with ethanol then pour solution into water
- If the mixture turns cloudy then lipids are present
- This is due to lipids’ insolubility in water
Colorimetry definition:
The process to determine the concentration of glucose in a solution.
How does coloimetry work?
Visible light goes through a filter and then through the solution then reaches a photocell. The opacity is an indicator of how much glucose has reacted, The a mount of light that goes through is recorded.
What can be the stationary phase in thin-layer chromatography?
- Cellulose chromatography paper
- Thin-layer chromatography plate
What is in the mobile phase in thin-layer chromatography?
- Solvent for molecules to be identified:
- Water for polar molecules
- Ethanol for non-polar molecules
What is the formula for Rf value?
Distance travelled by each solute/ distance travelled by the solvent
How are molecules identified through chromatography?
They each have their own Rf value
