Proteins 2

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  • Created by: Lotto65
  • Created on: 06-12-16 17:47
What is conformation?
The 3D structure of a protein
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What sort of shape do most proteins have?
Globular shape
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What determines the conformation and folding of a protein?
The sequence of amino acids
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Where are proteins synthesised?
Ribosomes
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Will polypeptides with the same amino acid sequence have the same conformation?
Yes
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What stabilises a globular protein structure?
Intramolecular bonds between amino acids
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When does intramolecular bonding occur?
When the polypeptides are brought together in the bonding process
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Give an example of a protein pump that switches reversibly between conformations
Sodium-potassium pump in a cell membrane
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True/false: The conformation of most proteins is delicate and can be easily damaged
True
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What is denaturation?
The damaging of the conformation of a protein due to chemicals or conditions
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How does heat cause denaturation?
Heat vibrations break intramolecular bonds between amino acids and causes conformation to change
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Is heat denaturation irreversible?
Yes - almost always
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Give an everyday example of heat denaturation
Egg white which has proteins denatured by heat so their new conformation is insoluble so egg white goes from liquid to solid
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What is the name of the protein in egg white?
Albumin
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How does pH cause denaturation?
Breaks intramolecular bonds with protein molecule
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Do proteins have an optimum pH at which their conformation is ideal?
Yes
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What will happen if you increase or decrease the pH too much?
The conformation of the protein will initially stay the same but then it would denature
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Name the five functions of proteins
Carbon dioxide synthesis; hormones, immunity, pigments, structure
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Name an acronym to remember the functions of proteins
CHIPS
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What is the name of the enzyme that catalyses the photosynthesis reaction?
Rubisco
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Name a hormone that causes cells to absorb glucose and lower blood glucose concentration
Insulin
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Where will you find insulin?
Pancreas but dissolved in the blood and binded to insulin receptors in cell membranes
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The bonding of insulin to an insulin receptor is reversible/ irreversible
Reversible
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What is another word for an immunoglobulin?
Antibodies
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What do antibodies do?
Help the body's immune system by binding to antigens on pathogens
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How does the body have immunity to many different diseases?
The immune system can make a range of immunoglobulins specific to specific antigens with a certain binding site
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Name a pigment that makes the rod cells in the retina light sensitive?
Rhodopsin
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How does rhodopsin work?
It has a non-amino acid part that absorbs photons of light. When it does this the rod cell sends a nerve impulse to the brain
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What is the name of the non-amino acid part of rhodopsin?
Retinal
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What type of protein is collagen and spider silk?
Structural protein
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What is the structure of collagen?
Three polypeptides wound together in a rope-like conformation
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Where is collagen used?
In the skin to prevent tearing; In bones to prevent fractures and in tendons or ligaments to give tensile strength
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What is spider silk used for?
Making webs to catch flies or to suspend spiders
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What properties of spider silk allow its function?
Very high tensile strength and gets stronger when stretched so resists breakage easily
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Name the process by which ribosomes synthesise proteins
Translation
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List reasons why the same 20 amino acids are used
They were the ones produced by chemical processes on Earth before life; They are the ideal ones so natural selection favours them; all life evolved from a single ancestral species with these amino acids - cannot change repertoire by removing or add
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How many polypeptides in hemoglobin?
4
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Give the name of a membrane protein
Integrin
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What is the structure of integrin?
Two polypeptides with a hydrophobic portion embedded in the membrane. The two polypeptides can work adjacent to each other or unfold and move apart
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Name a protein consisting of one polypeptide
Lysozyme
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What is lysozyme involved in?
The secretion of nasal mucus and tears; it kills bacteria by digesting peptidoglycan in cell walls
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Are amino acids acidic, basic or amphoteric?
Amphoteric
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What property does this give amino acids in that they are amphoteric?
They can ionise
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What do amino acids always contain?
Carbon, nitrogen, hydrogen and oxygen
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What can amino acids also contain?
Sulfur and potassium
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What type of reaction is polymerisation?
Condensation
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What is the name of the bond between amino acids?
Peptide bond
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What is primary structure?
The sequence of amino acids
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What is the name of the bonds in peptides that attach to sulfur?
Disulfide bridges
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Give an example of a peptide with a primary structure
ADH
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What is secondary structure?
The way the primary structure folds/ coils
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What causes a chain to pull into a helix?
Hydrogen bonds
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Give two examples of proteins with a secondary structure
Keratin, spider silk
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Where are the hydrogen bonds in keratin?
Every 4th acid
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How else can you describe the structure of spider silk?
Pleated sheet
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What sized proteins have a tertiary structure?
Large proteins
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What tends to be the shape of proteins with a tertiary structure?
Globular
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What causes the globular shape of proteins with a tertiary structure?
IM forces, H bonds, disulphide bridges, Ionic bonds, hydrophobic and hydrophilic interactions
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Which part of a globular protein is hydrophobic?
Inside
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Which part of a globular protein is hydrophilic?
Outside
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What creates a fibrous tertiary structure?
When the chains line up next to each other
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Can proteins with a tertiary structure dissolve?
Yes as water fills the gaps but not in the hydrophobic centre
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Give two examples of proteins with a tertiary structure
Myoglobin and immunoglobulins
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What technique is used to determine the tertiary structure of a protein or macro-molecule?
X-ray crystallography
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What classifies proteins as having a quarternary structure?
More than one polypeptide chain; or a prosthetic group
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What is a prosthetic group?
Something in a molecule other than amino acids
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What does the haem group in haemoglobin contain?
Iron
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Other cards in this set

Card 2

Front

What sort of shape do most proteins have?

Back

Globular shape

Card 3

Front

What determines the conformation and folding of a protein?

Back

Preview of the front of card 3

Card 4

Front

Where are proteins synthesised?

Back

Preview of the front of card 4

Card 5

Front

Will polypeptides with the same amino acid sequence have the same conformation?

Back

Preview of the front of card 5
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