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2. Molecular biology > Proteins > Flashcards

Proteins Flashcards

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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
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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 ).

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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
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4
Q

Be able to draw molecular diagrams to show the formation of a peptide bond.

A
  • Check book
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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

2. Molecular biology (9 decks)

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