Core Concepts Flashcards
Name 4 inorganic ions and their uses
- Mg2+, constituent of chlorophyll
- Fe2+, constituent of haemoglobin
- PO4 3-, Making nucleotides e.g. ATP
- Ca2+, structural component of bones and teeth
What is the difference between alpha glucose and beta glucose?
The first -OH group points down in alpha glucose but up in beta glucose
What are the functions of glucose?
- Energy source in respiration
- Intermediate in reactions
- Constituent of nucleotides
glucose + glucose =?
Maltose
Glucose + Fructose = ?
Sucrose
Glucose + Galactose = ?
Lactose
Describe a test for reducing sugars
Add benedicts reagent to the sample and heat at 70°c
A positive result will show a colour change from blue to red
How can you test for the presence of starch?
Add iodine solution
Positive result will show a colour change from Orange/Brown to black
Describe a test for fats and oils
Mix sample with pure ethanol and shake with an equal volume of water. Positive result will show a cloudy white precipitate.
What is the effect of a diet high in saturated fats?
Low density lipoproteins build up, atheromas get deposited in the coronary arteries, restricting blood flow. If the vessel becomes completely blocked a myocardial infarction occurs.
What is the effect of a diet high in unsaturated fats?
More high density lipoproteins are produced which carry harmful fats to the liver for disposal.
Describe the primary and secondary structure of proteins
Primary: The order of amino acids in the polypeptide chain
Secondary: Hydrogen bonding between molecules on the polypeptide chain forming alpha-helices and beta-pleated sheets.
Describe the tertiary and quaternary structures of proteins
Tertiary: further folding of the secondary structure
Quaternary: combination of more than one polypeptide group eg. Haemoglobin
How can you test for proteins?
Mix sample with biuret reagent
Postivie result will show a purple colour
Explain the naming of the ‘fluid mosaic model’
Fluid: phospholipid molecules can move
Mosaic: Proteins embedded in the bilayer vary in shape, size and pattern.
Model: We can not be entirely sure how accurate this representation of a membrane is.
Explain the arrangement of molecules within a cell membrane
Phospholipids form a bilayer with with the hydrophobic tails pointing inwards towards eachother.
Extrinsic proteins on the surface of the bilayer.
Intrinsic proteins extend across both layers of the phospholipid bilayer.
What is the function of extrinsic and intrinsic proteins?
Extrinsic: Provide structural support and act as receptor sites.
Intrinsic: Form carriers or channels to allow molecules to cross the membrane.
Explain the permeability if the cell membrane in terms of both lipid soluble and water soluble substances.
Lipid-soluble:
Can diffuse across the membrane
Water-soluble:
Polar molecules must pass through intrinsic proteins.
What is diffusion?
The movement of molecules down a concentration gradient, no energy is required.
Give 3 factors that will affect the rate of diffusion
1) Concentration gradient
2) Diffusion distance
3) Surface area of membrane
What is facilitated diffusion?
A form of diffusion that allows insoluble substances to cross a membrane. Occurs through intrinsic proteins.
Describe the 2 types of intrinsic protein
Channel Protein:
Hydrophilic channels allowing polar molecules to pass through the membrane according to the needs of the cell.
Carrier Protein:
Allow diffusion of larger molecules. A molecule attaches to a binding site on the carrier protein, changing its shape and releasing molecules on the other side of the membrane.
What is active transport?
The exchange of substances across a membrane using energy in the form of ATP.
Describe the process of Active Transport.
- A molecule/ion binds to the carrier protein
- ATP transfers a phosphate to the carrier protein
- The carrier protein changes shape, allowing the molecule to cross the membrane.
- The phosphate recombines with the ADP to form ATP
