Biological molecules Flashcards
What is a monosacchiride?
Single sugar molecule
What is a hexose sugar?
Sugars with 6 carbons
Difference between Alpha and Beta glucose…
In alpha the OH group is below the H and vice versa
How do monosacchirides join together? What bond is formed?
Join via condensation reactions forming a glycosidic bond
Maltose made of
2 glucoses
Sucrose made of
Glucose + Fructose
Lactose made of
Glucose + Galactose
Hydrolysis
Breaks disacchirides or polysacchirides down by adding a water molecule
Testing for a reducing sugar
Put solution in test tube
Add Bendict’s reagent
Heat in boiled water bath
Produces a coloured precipitate
Colour scale of Benedict’s reagent precipitate from lowest to highest concentration of sugar
Blue, Green, Yellow, Orange, Brick-red
Testing for a non-reducing sugar
To break down to monosacchirides, add dilute HCl to sample
Heat in water bath that’s been brought to a boil
Neutralise with sodium hydrogencarbonate
Carry out test with Benedict’s Reagent
What is meant by a reducing sugar?
Donates electrons to other atoms (reduces them) while it oxidises itself
What polysacchirides is starch a mixture of?
Amylose and Amylopectin
What is Amylose?
Long, unbranched chain of alpha glucose. 1-4 Glycosidic bonds giving it a coiled structure, this makes it compact so therefore good for storage.
What is Amylopectin?
Long, branched chain of alpha glucose. Side braches allow enzymes to break down the molecule to get to 1-4 and 1-6 glycosidic bonds easily, this means glucose can be released easily.
Starch is good for storage because…
It’s insoluble in water so doesn’t affect the water potential of the cell
Iodine test for starch
Add iodine dissolved in potassium iodide solution to sample.
Colour change from orange-brown to blue-black
What is the structure of cellulose?
Made up of long, unbranched chains of beta-glucose. Cellulose chains have alternating patterns so that hydrogen can make links between cellulose chains to form strong fibres.
Why is cellulose good for plant cells?
Provides structural support for plant cells
What is glycogen?
Main energy storage in humans.
What is glycogen’s structure similar to?
Amylopectin but with more branches
How does the structure of glycogen relate to its function?
Branches so that stored glucose can be released quickly - important for energy release in animals
Also a compact molecule which is good for storage.
What is a triglyceride? how is it formed?
One molecule of glycerol with 3 fatty acids bonded to it
condensation reaction - Ester bond formed between 2 OH groups releasing water
What makes lipids insoluble in water?
Have long hydrophobic tails
What is a phospholipid?
Similar to triglyceride but one of the fatty acid molecules is replaced by a phosphate group(hydrophilic)
How does the structure of triglycerides relate to their function?
Lipids contain more energy than carbohydrates
Insoluble so don’t affect water potential of a cell
How does the structure of phospholipids relate to their function?
Centre of the bilayer they make up is hydrophobic, so water soluble substances can’t easily pass through it
What is the monomer of a protein?
Amino acid
Dipeptide
Two amino acids joined together
Polypeptide
More than two amino acids joined together - proteins made up of one or more polypeptides
How do amino acids link?
- Linked via condensation reactions to form polypeptides
- bond formed between two amino acids is called a peptide bond
Primary Structure of proteins
Sequence of amino acids in the polypeptide chain
Secondary structure of proteins
- Hydrogen bonds form between amino acids in chain.
- This makes it coil into an alpha-helix or fold into a beta-pleated sheet
Tertiary structure of proteins
- Coiled and folded further
- Disulfide bridges form when two molecules of amino acid, cysteine, bonds to sulfur atom in the other.
- For proteins made of a single polypeptide chain, the tertiary structure forms their final 3D structure
Quaternary structure of proteins
- Some proteins made of several different polypeptide chains are held together by bonds
- contain non-protein (prosthetic groups)
Biuret’s test for proteins
- Test solution needs to be alkaline, so add sodium hydroxide
- Add Biuret’s reagent
- If protein present, solution should go from blue to purple
How do amino acids differ?
There are 20 amino acids that are common in all organisms and they differ only from their R group
Enzymes - structure and functions
- Usually spherical shape due to tight folding of polypeptide chains
- Soluble and have roles in metabolism and other enzymes synthesise large molecules
Antibodies - Structure and functions
- Involved in immune response.
- Made up of two light polypeptide chains and two heavy polypeptide chains bonded together
Transport proteins function
Transport molecules and ions across membranes
Structural proteins - structure and function
- Physically strong
- Consist of long polypeptide chains lying parallel to each other with crosslinks between them
- Include keratin and collagen
