B.1.2 Flashcards
Proteins
Amino Acids
What is a peptide bond?
- The covalent bond between two amino acids which are the monomers (building block molecules) of protiens.
- A bond between the carbon of the carboxyl end of the amino acid and the nitrogen of the amino group.
- This bond is formed through a condensation reaction.
Amino Acids
What is a polypeptide?
- A chain of amino acids.
- The polymer formed from the condensation reactions.
- A polypetide will then, be folded and further bonds formed, to turn it into a functional protein.
- It is the PRECURSOR to a protien –> translation during protein synthesis forms polypetides.
Amino Acids
What does the term ‘denature’ mean?
The loss of a proteins shape leading to the loss of its function, is called denaturation.
- Can occurr when proteins are exposed to harsh environments, due to weaker bonds breaking.
- If the shape of a protein changes, it will decrease/ compeltely lose its function.
Amino Acids
Making a Dipeptide
Formed by condensation reactions.
- The hydroxyl is removed from the carboxyl end of the first amino acid and a hydrogen is removed from the amine end of the second amino acid.
- The Carbon from the carboxyl forms a peptide bond to the nitrgoen of the amine group.
- THe OH and H combine to form water.
Amino Acids
What makes an amino acid essential?
There are 9, out of the 20, amino acids that we must eat in their exact form, as we have no ability to construct them from parts.
- These are called essential amino acids –> we cannot synthesise them in the body.
- Thus, we must have a diet full of protein so we get the essential amino acids needed to make functional proteins.
Amino Acids
Important Proteins in the body
- Hemoglobin –> transports oxegyn on RBCs
- Digestive enzymes –> to break down food.
- Collagen (ligaments and tendons) + Keratin (hair and nails) are structural proteins.
- Histones –> that DNA is wrapped around
- Hormones –> like insulin.
Amino Acids
Impact of High Temperatures and atypical pH levels.
- Globular proteins are folded, rather than straight chains. –> fold done through many types of bonds including weaker bonds (including H bonds)
- At high temps/ acidic or alkaline environments –> the weak bonds break and the protein denatures.
- The protein can renature/ rebond when conditions return to normal –> therefore denaturation is often temporary.
Protein Strcture
What is an R group?
Every amino acid has a carboxyl group branched off a central carbon.
- The additional chain of elements also coming down from the central carbon is unique to each amino acid –> The R-group is what makes amino acids unique and gives it its chemical properties.
Protein Structure
What are hydrophobic interactions?
- If amino acids are NON-POLAR, they interact in the presence of water.
- Non-polar R groups are not inherently attracted to each other but they move inwards away from the polar water molecules.
- When they pull inwards –> R groups move towards each other which is called a hydrophobic interaction.
Protein Structure
What is a Disulfide bond?
- The amino acid cysteine has an R-group that is a SULFUR atom bonded to a hydrogen.
- If two cysteine molecules are near each other –> hydrogens can be removed and the two sulfur molecules can covalently bond to one another.
- This covalent bondis called a disulfide bond (VERY STRONG.) –> the strongest bond in the tertiary bonding/protein structure.
Protein Structure
Levels of Protein Structure: Primary Structure.
The specific SEQUENCE of amino acids that are bonded together to create a straight linear chain of amino acids.
- The protein structure is determined by the DNA CODE in the gene that codes for the protein.
- Based on the DNA triplets, the specific amino acids are added –> which give the protein its primary structure.
- THE PRIMARY STRUCTURE IS ALTERED BY MUTATIONS (as they change the DNA)
Protein Structure
Levels of Protein Structure: Secondary Structure.
After the polpetide CHAIN is complete, the protein begins folding.
- All amino acids have some charge – the amine group has a slight positive charge and the carboxyl a slight negative charge.
- These charges cause hydrogen bonds to form between the amino acids in the chain.
- It comes from the carboxyl and amine groups it is consistent and forms a pattern throughout –> either an alpha helix or a beta pleated sheet.
Protein Structure
Levels of Protein Structure: Tertiary Structure.
Proteins that are globular have different bodns between the R-groups of their amino acids.
- This causes a non-uniform and unique set of FOLDS that give the protein its trademark shape.
- The bonds that contribute to tertiary structure include: IONIC bonds between CHARGED R-groups, HYDROPHOBIC interactions between NON-POLAR R-groups, H-Bonds between polar R-groups and disulfide bridges between cystienes.
Protein Structure
Levels of Protein Structure: Quaternary Structure.
Multiple polypetides join together to make one protein.
- The polypeptide bond to one another using the same type of bonds as for tertiary structure but between R-groups of different polypeptides.
Protein Structure
Alpha Helix vs Beta Pleated Sheets.
Secondary structure consists of consistent hydrogen bonds between the amine group of one amino acid and the carbozyl of another.
1.) IN ALPHA HELIX:
- the polypeptide is wound into a helix shape and hydrogen bonds form between the turns of the helix.
2.) IN EBTA-PLEATED SHEET:
- Sections of the polypeptide are run in opposite directions and hydrogen bonds form between the lines giving a pleated (FOLDED) shape because of the bond angles.
