proteins

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  • Created by: EClou
  • Created on: 17-04-15 19:32
what elements make up a protein?
oxygen, carbon, nitrogen, hydrogen and some times sulphur
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give 5 functions of proteins
1. structural components of muscle and bone, 2. membrane carriers and pots for processes such as active transport or facilitated diffusion, 3. enzymes, 4. hormones, 5. antibodies
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how many amino acids in a dipeptide?
2
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what is a polypeptide chain?
a protein made of many amino acid monomers
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what is the specific name for the bond formed when to amino acids join together, what type of bond is it and how is it formed?
it is called a peptide bond, it is a covalent bond formed by a condensation reaction
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what reaction occurs to break a polypeptide bond?
a hydrolysis reaction
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where does the peptide bond form?
between the H of the amino group and the OH of the carboxylic acid group
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can a protein have more than one polypeptide chain?
oui oui
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why are amino acids in polypeptide chains sometimes referred to as residues?
because part of the molecule is lost in the condensation reaction to make the peptide chain
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where are polypeptide and proteins made and what is this process called?
in the ribosome of cells this is called protein synthesis
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what is the role of mRNA?
this molecule is responsible for putting the amino acids in the correct order for a specific polypeptide chain.
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what else are involved in the breakage and makeage of peptide bonds and in what way are they involved ?
enzymes catalyse the making/breaking
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what type of enzyme is used where might they be found in a cell?
protease in a LYSOSOME in the cell
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what are 2 examples of organisms continually rebuilding and breaking down proteins?
1. Hormones - must be broken down to control their effects so any cell targeted by a hormone contains protease to break it down, 2. ageing - wrinkling due to skin being less able to rebuild collagen and other proteins.
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what is the primary structure of a protein responsible for and how does it effect the protein?
the sequence of the amino acids for each specific polypeptide, this determines the structure and so therefore the function and properties of the protein.
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what is the secondary structure of a protein?
this occurs when the polypeptide chains coil into ALPHA HELICES or fold into BETA PLEATED SHEETS which are held in place by hydrogen bonds
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what is the R group?
the variable group - determining the different amino acids
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what is the chain formed in the primary structure held together by?
peptide bonds
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what is the tertiary structure?
this is further folding to give a 3D shape that is specific to the function of the protein e.g enzymes require active site specific to substrate
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how is the tertiary structure held in place?
1. hydrogen bonds between slightly -ve O & slightly +ive H, 2. disulphide bridges between 2 cysteines, 3. ionic bonds - some R groups cause the AA to be slightly +ve/-ve, 4. hydrophobic (around the outside of globular proteins) and hydrophilic
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when is there a quaternary structure and what is it? and give 2 e.g.s
this only occurs in proteins where there is more than 1 polypeptide chain/pptd & inorganic component e.g. haemoglobin or insulin.
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what is denaturation?
this is when the whole tertiary structure unravels due to excess heat so that the protein can no longer function and won't return to its original shape even after cooling
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why does it occur?
this occurs when heat is applied causing increased kinetic energy in the molecules, they can them overcome the weak bonds that hold together the tertiary structure.
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what is the shape of a globular and fibrous protein and what are their roles?
g - rolled up in a ball - has a metabolic role, f- fibres formed- has a structural role
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which is soluble in water?
globular
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what is a prosthetic group and give and example of one in a molecule/
a non-protein component that forms a prominent part of a functioning protein molecule - e.g the harm group (Fe2+ ion) in haemoglobin
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describe the structure of a haemoglobin molecule
quaternary structure with 4 polypeptide units made of 2 alpha and 2 beta chains, it is globular and contains 4 haem groups
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describe the structure of collagen
fibrous protein with 3 polypeptide chains linked by hydrogen bonds and featuring covalent bond cross links to form a fibil
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give 4 examples of where collagen is used
1. tendons connecting muscles to bones - allows muscles to pull bones, 2. artery walls to protect arteries from blood pumped at high pressure, 3. bones formed of collagen, 4. cartilage and connective tissue.
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what is the function of haemoglobin?
to transport oxygen from the lungs to the tissue.
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describe a test for the presence of protein
Biurets test - add sodium hydroxide and gently mix, add copper sulphate slowly, if protein present lilac colour will be seen.
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Card 2

Front

give 5 functions of proteins

Back

1. structural components of muscle and bone, 2. membrane carriers and pots for processes such as active transport or facilitated diffusion, 3. enzymes, 4. hormones, 5. antibodies

Card 3

Front

how many amino acids in a dipeptide?

Back

Preview of the front of card 3

Card 4

Front

what is a polypeptide chain?

Back

Preview of the front of card 4

Card 5

Front

what is the specific name for the bond formed when to amino acids join together, what type of bond is it and how is it formed?

Back

Preview of the front of card 5
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