B1.2 (proteins) (from SME, 2.3.1, AI) Flashcards
What are proteins made of?
Proteins are polymers made of monomers called amino acids
What determines the shape and function of a protein?
The sequence, type, and number of amino acids
List five types of proteins
- Enzymes
- Cell membrane proteins
- Hormones
- Immunoproteins
- Transport proteins
- Structural proteins
- Contractile proteins
Why are proteins crucial for life?
All genes code for proteins, making all reactions necessary for life dependent on proteins
What are the building blocks of polypeptides?
Amino acids
How many amino acids are commonly found in polypeptides?
20 amino acids
What is the general structure of an amino acid?
A central carbon atom bonded to an amine group, a carboxylic acid group, a hydrogen atom, and an R group
What is a peptide bond?
A bond formed when a hydroxyl group is lost from one amino acid and a hydrogen atom is lost from another
What reaction occurs during the formation of a peptide bond?
Condensation reaction
What are dipeptides and polypeptides?
Dipeptides are formed by two amino acids; polypeptides are formed by three or more amino acids
What happens during hydrolysis reactions?
Water is added to break peptide bonds, resulting in amino acids
True or False: All organisms use the same 20 amino acids.
True
What are essential amino acids?
Amino acids that must be obtained through the diet
How many amino acids can humans synthesize naturally?
11 amino acids
Fill in the blank: The amino acids are usually abbreviated to _______.
[three letters]
What is the significance of the R group in amino acids?
It determines the properties of each amino acid
What are the hypotheses regarding the use of only 20 amino acids in proteins?
- Only these 20 were available at the origins of life
- They are diverse enough for wide protein functions
- All organisms share a common ancestor
What is the Central Dogma of molecular biology?
All genes code for proteins, and proteins determine an organism’s characteristics
How many possible combinations exist for a polypeptide chain of 50 amino acids?
20^50
1.13 x 10^65 combinations
What is required to code for each amino acid in a polypeptide?
Three consecutive DNA bases
What is the genetic code?
The sequence of DNA bases that codes for the amino acid sequence of polypeptides
What is the average length of a protein?
300 amino acids
Secondary protein structures are normally stabilised by hydrogen bonds created between:
–NH groups of peptide bonds and –C=O groups of other peptide bonds found in the same chain.
descriptions of primary, secondary and terinart structure of peoteins
The primary structure describes a chain of amino acids
the secondary structure: folding into an alpha helix or beta pleated sheet,
Tertiary structure: folded chains can further coil up and create three-dimensional structures, by the R groups interacting
Quarternary: the arrangement of two or more polypeptide chains to form functional proteins.2
r groups can be
polar or non polar
fibrous proteins are insoluble because
they have non polar aa on the surface
