2. Amino Acids and Proteins Flashcards
(37 cards)
Define polymer.
Large molecule made from joining many similar or identical monomers together.
Define assimilated.
Taken up by the body and used.
Define monomer.
Small molecule which can be joined with similar or identical molecules to form polymers.
Define condensation reaction.
A reaction joining two or more molecules involving the removal of water.
Define hydrolysis reaction.
A reaction breaking down a large molecule into its constituent parts by the hydrolysing the connecting bond with water.
What elements are amino acids made up of?
Nitrogen, carbon, hydrogen and oxygen.
Give examples of globular and structural proteins.
Globular proteins:
- Enzymes - biological catalysts that control biochemical reactions.
- Transport proteins such as haemoglobin.
- Signal proteins such as hormones.
- Contractile proteins such as actin and myosin. (Involved in muscle contraction).
- Defensive proteins such as antibodies.
Structural proteins:
- Keratin which is found in nails and hooves.
- Collagen which is found in tendons.
Draw the general structure of amino acids.
H H O | | | | N — C — C | | | H R OH ^ ^ ^\_\_ Carboxyl group. | |\_\_ R group - differs between amino acids. |\_\_ Amine group.
Describe the formation of a dipeptide.
- Two amino acids join together to form a dipeptide by a condensation reaction.
- The hydroxyl (OH) group from one amino acid reacts with the hydrogen from the amine group of another amino acid.
- This forms water and a peptide bond between the N in the amine group, and the C in the carboxyl group.
- This peptide bond creates the dipeptide.
How would you name 2, 3, 4, and 5 amino acids joined together?
2 = dipeptide. 3 = tripeptide. 3+ = polypeptide.
Draw a condensation reaction.
H H O H H O
| | | | | | | |
N — C — C N — C — C
| | | | | |
H R1 OH H R2 H
|_________|—–> H2O
|
V
H H O H H O
| | | | | | | |
N — C — C — N — C — C
| | | |
H R1 R2 H
Most of the food we eat is composed of _________, which are too ______ to be __________ into the __________ through the _____________________. During ______, _______ break down (__________) __________. Once _________, __________ molecules can be ___________.
Most of the food we eat is composed of POLYMERS which are too LARGE to be ABSORBED into the BLOODSTREAM through the SMALL INTESTINE MEMBRANE. During DIGESTION, ENZYMES break down (HYDROLYSE) POLYMERS. Once ABSORBED, SMALLER molecules can be ASSIMILATED.
Draw a hydrolysis reaction.
H H O H H O
| | | | | | | |
N — C — C — N — C — C
| | | |
H R1 R2
|_________|
Amino acids are the basic ______ of __________, which combine to make a ________ called a _________. Many amino acids join together in ___________ via _________ reactions to make a _______________ chain. A _________ chain will always have a ________ group at one end, and a ________ group at the other end. The number of _________ bonds will always be __________ than the number of amino acids. The ______ in a __________ chain is determined by the _____________. (_______ sequence = _______ of amino acids).
Amino acids are the basic MONOMER of PROTEINS which combine to make a POLYMER called a POLYPEPTIDE. Many amino acids join together in POLYMERISATION via CONDENSATION reactions to make a POLYPEPTIDE chain. A POLYPEPTIDE chain will always have aN AMINE group at one end, and a CARBOXYL group at the other end. The number of PEPTIDE bonds will always be ONE LESS than the number of amino acids. The ORDER in a POLYPEPTIDE chain is determined by the DNA BASE SEQUENCE (TGAC sequence = ORDER of amino acids).
How many levels of protein structure are there, and what are they called?
Four: Primary 1^o Secondary 2^o Tertiary 3^o Quaternary 4^o
Draw a representation of the primary structure.
O H
|| |
C —( ) — ( ) —- ( ) — ( ) — N
| ^ ^ |
OH | |___ Amino acids. H
^ |__ Peptide bond. ^__ Amine group.
|
|___ Carboxyl group.
Define the primary structure.
The primary structure of a protein is a polypeptide chain. This structure is determined by the number and sequence and number of amino acids in the polypeptide chain.
Why do proteins differ from each other?
Different proteins have different primary structures, meaning bonds between R groups form in different locations. This gives them a different tertiary structure and shape.
How does the primary structure relate to function?
Different proteins have different primary structures, meaning bonds between R groups form in different locations. This gives them a different tertiary structure and shape, optomisibg them for a different function.
Define secondary structure.
This described the way the polypeptide chain folds into beta pleated sheets, or coils into alpha helixes.
Describe the secondary structure of a protein with the aid of diagrams.
Secondary structure is a polypeptide chain coiled into an alpha helix, or folded into a beta pleated sheet.
Alpha helix:
- Coil with a hydrogen bond between every fourth amino acid. (Between oxygen bonded to carbon, and the hydrogen bonded to nitrogen).
Beta pleated sheet:
- Chains run antiparallel to each other, and the structure is pleated. Hydrogen bonds (as above) attach the chains together.
See notebook for diagrams.
Define the tertiary structure.
The tertiary structure of a protein is the further folding of a polypeptide chain into a specific, complex 3D shape. It contains alpha helixes, beta pleated sheets as well as random coils and turns.
How is the tertiary structure maintained?
Bonding between R groups.
Hydrogen bonds, ionic bonds and disulphide bridges.
In a ________ structure, weak ________ bonds are _________, however they are easily _______. There are also _______ bonds forming between _____________ R groups. These bonds are __________ broken by __________. In addition there are ________________, which are strong _________ bonds which form between ________ containing __________. (eg. ___________). A _________ of ______ or higher us required to ________ them.
In a TERTIARY structure, weak HYDROGEN bonds are NUMEROUS, however they are easily BROKEN. There are also IONIC bonds forming between OPPOSITELY CHARGED R groups. These bonds are EASILY broken by PH CHANGE. In addition there are DISULPHIDE BRIDGES, which are strong COVALENT bonds which form between SULPHUR containing R GROUPS. (eg. CYSTEINE) A TEMPERATURE of 70^oC or higher us required to BREAK them.
