Proteins Flashcards
1
Q
Give 5 examples of proteins in a human body, what affect they have on the human body and the monomers.
A
- Enzymes, hormones, protein pumps, receptors, agents of the immune system
- 16% of the body is composed of proteins
- Proteins have an impact on the physiology and metabolic rate of a body
- Monomers of proteins are amino acids
2
Q
What is a polypeptide and how are they related to proteins?
A
- Polypeptides are a number of linked peptides
- The basic units are amino acids, a carboxyl group (-COOH) and an amino group (-NH 2 ).
3
Q
How are peptides formed?
A
- Amino acids bind together in a condensation reaction to form a polypeptide and water molecules
- Breaking down again occurs during hydrolysis
- Peptide bond is (O=C-N-H)
- Polypeptides=proteins
- Peptides itself are smaller than proteins
4
Q
Be able to draw molecular diagrams to show the formation of a peptide bond.
A
- Check book
5
Q
What makes up a sequence of polypeptides and where are they produced?
A
- 20 amino acids can be linked together in any sequence giving a huge range of possible polypeptides
- 20 ^n different types of polypeptides (n=number of amino acids in the polypeptide)
- Synthesis of Polypeptides occurs on ribosomes during translation
- Most organisms use the 20 amino acids in the same genetic code, there are some exceptions
6
Q
What are genes and what do they do?
A
- Genes are sections of DNA that contain the instruction (plan) for all polypeptides of an organism
- Genes code for the amino acid sequence in polypeptides
7
Q
How many genes code for polypeptides?
A
- A gene codes for one polypeptide which have specific functions
- There are proteins that can be made of one or more polypeptides linked together
- E.g. Hemoglobin, consists of four polypeptide chains and a non-protein part
8
Q
What affects the structure and ‘conformation’ of a protein?
A
- The R group in amino acids determines the types of bonds and interactions with other molecules that they can make
- This defines how the polypeptide chain(s) fold up in the protein and affects the three-dimensional structure
- This is called conformation
9
Q
What can change the protein’s conformation and what can cause this?
A
- A change in the order of amino acids
- This results in a change of shape or loss of function
- Gene mutations can be the cause for change in the order of amino acids
10
Q
What are the different levels of organization within proteins in increasing complexity?
A
- The primary structure is the sequence of amino acids in a protein. It defines all aspects of the structure and function of a protein
- The secondary structure involves the folding of the chains on themselves to form beta pleated sheets or alpha helixes
- The tertiary structure is when the polypeptide folds and coiled to form a complex three-dimensional shape
- The quaternary structure only exists in proteins made up of two or more polypeptide chains. Multi-subunit complex e.g. hemoglobin
- Bonds such as covalent, hydrogen and ionic bonds can be formed
11
Q
What is a genome and a proteome? What is proteome used for?
A
- Genome: a complete and unique DNA content of an organism
- Proteome: the unique set of proteins that are coded by their genome of an organism
- The proteome of a cancer patient’s cancer cells is analyzed to determine if a particular chemotherapy will be successful. Basically is it is used to help treat certain cancers.
- Every individual has a unique proteome, each one has a slightly different set of proteins due to the difference in amino acid sequences
12
Q
What are the two groups in which proteins are divided into?
A
- Proteins are divided into groups depending on their chemical structure and functions
- The most common division is based on their solubility in water
- There are globular and fibrous proteins
13
Q
Give 5 details of globular proteins.
A
- They are globe-life or spherical
- Take part in cell metabolism
- Consist of complex polypeptide chains
- Example: hemoglobin (two alpha and two beta chains)
- They are soluble in water because their hydrophobic R groups are folded into the core of the molecule
14
Q
Give 5 details of fibrous proteins.
A
- Are more like fiber, long and thread-like
- Made out of long chains
- The hydrophobic R groups are exposed, molecule is insoluble
- They are found in structural parts of organisms e.g. tendon and skin
- Examples: collagen and keratin
15
Q
In what processes do proteins work in living organism?
A
- They are involved in most metabolic reactions
- E.g. receptors, transport channels, pumps and enzymes
- Living organisms synthesis many different proteins with a wide range of functions
16
Q
Give 6 examples of proteins and their functions.
A
- Rubisco: an enzyme involved in the fixation of CO2 in chloroplasts
(Globular) - Insulin: a hormone produced by the beta cells of the pancreas, glucose uptake from the blood (Globular)
- Immunoglobulin: antibodies, involved in fighting infections using cell recognition and binding to antigens (Globular)
- Rhodopsin: a protein linked to pigment, found on the membrane of rod cells of the retina (low light detected) (Globular)
- Collagen: structural protein, found in muscles, tendons and ligaments, giving strength. Found in skin and bones to prevent tearing and fractures. Made out of three different types of polypeptide chains (Fibrous)
- Spider silk: protein produced by spiders for their webs, can be extended and is resistant to breaking (Fibrous)
17
Q
Compare globular proteins with fibrous proteins.
A
- Globular: round, soluble, more sensitive to changes in temperature/pH, used for catalysis, transport
- Fibrous: strands/sheets, insoluble, structural roles
18
Q
What is denaturation and what are 3 outcomes of this process?
A
- The process in which proteins lose their secondary and tertiary structures (sometimes quaternary)
- The hydrogen bonds between R-groups and amide groups of two different amino acids is disrupted
- Active sites lose their shapes
- The entire enzyme loses it enzymatic properties
19
Q
What effect does temperature have on proteins?
A
- Proteins have an optimum temperature at which they work best, any deviation from these values influences the functionality of the proteins
- Egg whites, are used in denaturation experiments. When the proteins in the egg white lose their conformation, the interaction between certain amino acids will be changed.
- The protein loses its form and function
- Peptide bonds between amino acids (which are next to each other) do not break
- The primary structure is not damaged
- The secondary and tertiary and sometimes the quaternary structures are irreversibly changed
20
Q
What effect does pH have on proteins?
A
- The pH of a solution can affect the functionality of a protein
- Strong alkaline/acidic solutions break the bonds between the amino acids (which are not next to each other) or polypeptide chains of quaternary proteins
- The protein denatures and loses functionality
