Lipids and Proteins - B2 Flashcards
What are amino acids?
a single molecular repeating unit
How many common amino acids are there?
20
Which type of amino acid can be made by our bodies?
Non-essential amino acids can be made by our bodies, but we must get essential amino acids from our diet.
What are the 4 different groups in the structure of amino acids?
-Variable group (R group)
-Carboxylic acid group (carboxyl)
-hydrogen group
-Amine group (amino)
What reaction is used to bond two amino acids?
Condensation, which produces H2O.
What is the bond called that bonds two amino acids?
peptide bond
What are two amino acids bonded together called?
Dipeptide
What is another name for a protein?
Polypeptide
What are polypeptides?
A long chain of amino acids.
Which structure stages do all proteins go through?
1-3, only some go through 4.
What does every R group have different from each other?
They have a different amino acid.
What is the primary structure?
The primary structure is the no. and sequence of amino acids in a polypeptide chain.
Why do proteins differ from each other?
Because their primary structures are different from each other.
What are the two things that are formed in the secondary structure?
Alpha helix or beta pleated sheet.
Do alpha helix and beta pleated sheets form on the same chain?
Yes.
What is used to form the alpha helix and beta pleated sheet?
Using 1 polypeptide chain and hydrogen bonds.
What is the structure of an alpha helix?
Hydrogen bonds form between every 4th amino acid which causes the polypeptide chain to coil. It still has peptide bonds.
How are beta pleated sheets formed?
Hydrogen bonds form downwards.
What is the structure of the tertiary structure?
Further folded into a specific complex 3D shape. It is just a single polypeptide chain, and the way it folds depends in which bonds are present.
What is the shape of the tertiary structure held together by?
This shape is held together by bonds between R groups of different amino acids.
Which bonds are responsible for the tertiary structure?
Hydrogen bonds, ionic bonds, disulphide bridge(bond)
Are hydrogen bonds weak or strong?
They’re weak.
Are ionic bonds weak or strong?
They’re also weak, and they form between oppositely charged R groups.
What type of bond are disulphide bridges?
Covalent bonds, which form between two sulphur containing R groups found in cystine amino acids. The sulphur atom in one cystine bonds the sulphur atom in another cystine.
What are the two things that could destroy or denature the bonds?
Heat or pH.
What is the quaternary structure?
Some proteins consist of two or more polypeptide chains joined together.
What are some examples of a protein in the quaternary structure?
Hemoglobin, which has 4 polypeptide chains.
Other examples include: insulin, collagen, ribosomes and DNA polymase
Are there any new bonds in the quaternary structure?
No
What is the chemical test for proteins?
Biuret test:
-Add a few drops of sodium hydroxide solution
-Add a few drops of dilute copper sulphate solution(on the side of the test tube to release it slower)
-Shake it gently
-Positive result: mauve/purple/lilac
What is the chemical test for lipids?
Lipid(emulsion) test:
-Dissolve the test sample by shaking with 2cm^3 ethanol
-Pour resting solution into water in a test tube
-Positive result: white emulsion is formed.
What is a reducing sugar?
It donates it’s electrons and reduce other substances
What are the two types of lipid?
Triglyceride and phospholipids
What are triglycerides made from?
One glycerol molecule and three fatty acids.
Is triglyceride a monomer or polymer?
It’s not a monomer or a polymer, just a molecule.
Where are triglycerides stored?
Stored in fat cells -> calories the body doesn’t need.
Why do hormones release triglycerides?
For energy between meals
What are some of the functions of lipids/triglycerides?
Lipids store energy, provide insulation, form water-repellent layers on leaves, and provide building blocks for hormones.
What are the two types of fatty acid?
Saturated and unsaturated.
What is a saturated fatty acid?
There are no double bonds in the hydrocarbon chain, and it has the most hydrogen possible.
Does the carboxyl group change for any fatty acid?
No it doesn’t.
What is an unsaturated fatty acid?
It has a double bond in the hydrocarbon chain. If there is only 1 double bond, it’s monounsaturated, but if it has more than one double bond, it’s polyunsaturated. There is no hydrogen saturation.
What is the basic structure of fatty acids?
-Typical fatty acid contains 12-18 carbons, though some have as few as 4 and as many as 36.
-It’s the same basic structure for saturated/unsaturated fatty acids.
Which atom links the fatty acid to the glycerol?
The carbon atom.
What is the difference between a phospholipid and a triglyceride molecule?
It has gained a phosphorus molecule and lost a fatty acid, so it is now a phosphate head and 2 fatty acid chains.
Which of the phosphate head and fatty acid tail is hydrophobic and hydrophilic?
Phosphate head- hydrophilic
Fatty acid tail- hydrophobic
What do the disulphide molecules form when they face each other?
They from a barrier - double layer barrier known as the cell’s double membrane.
