Proteins - Fibrous and Globular

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  • Created by: shyde7
  • Created on: 26-04-16 15:37
What is the sequence of amino acids like in fibrous proteins?
They have a regular, repetitive sequence.
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Are fibrous proteins soluble in water or insoluble?
Insoluble.
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Why would the structure of amino acids and insolubility be a good thing?
They allow the protein to form fibres which have a structural function.
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What shape do globular proteins take?
They tend to roll into an almost spherical shape.
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Why do globular proteins roll into a spherical shape?
In order to have the hydrophobic R groups on the inside towards the centre of the molecule, and the hydrophilic R groups on the outside.
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Are globular proteins soluble?
Yes, because water molecules can easily cluster around the globular molecules and bind to them.
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Why is it good that globular proteins often have very specific shapes?
Because this helps them take on roles such as enzymes, hormones and haemoglobin.
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Is collagen a fibrous or globular protein?
It is a fibrous protein.
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What is the function of collagen?
To provide mechanical strength.
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Why do artery walls have a layer of collagen?
To prevent the artery bursting when withstanding high pressure from blood being pumped by the heart.
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What allows muscles to connect to bones, allowing the muscles to pull on them.
Tendons, which are made of collagen.
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Which major structural components of the bosy are made from collagen and then reininforced with calcium phosphate?
Bones.
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Which softer structural components is also made from collagen?
Cartilage and connective tissue.
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Which amino acid is Keratin rich in?
Cysteine
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Because Keratin has a lot of cysteine, which bond does it have a lot of?
Disulfide bridges.
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What can we say about the molecule, knowing it has both disulfide liks and hydrogen bonds?
The molecule is very strong.
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Keratin is found wherever a body part _?
Needs to be hard and strong.
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Name 3 components made from Keratin.
Fingernails, Claws, Hoofs, Horns, Scales, Fur and Feathers.
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How does Keratin protect against infection?
It is waterproof, and so protects from water-borne pollutants. It also provides mechanical protection and an impermeable barrier to infection.
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What two things makes Elastin strong and extensible?
Cross-linkin and coiling.
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Where is Elastin found?
Wherever living things need to stretch or adapt their shape as part of life processes.
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Why is elastin useful in skin?
Because it allows our skin to stretch over our bones and muscles.
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Which other two organs is elastin useful in?
Our lungs to help them inflate/deflate and in our bladder to expand to hold urine.
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Why is elastin used in our blood vessels?
Much like collagen, it allows the vessels to maintain their shape while resisting pressure.
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Is haemoglobin a fibrous or globular protein?
Fibrous.
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What is the quaternary structure of haemoglobin made of?
Four polypeptides: two alpha-globin chains and two beta-globin chains.
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What holds the shape of the haemoglobin molecule together?
Hydrogen bonds, Ionic bonds, Disulphide bridges and Hydrophilic and hydrophobic interactions.
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What gives the haemoglobin molecule its specific shape?
Interactions between the polypeptides.
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Each polypeptide chain of haemoglobin contains what?
A haem group.
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What is special about the haem group of haemoglobin?
It is not made of amino acids.
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What is another name for the haem group of haemoglobin?
The prosthetic group.
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What is a prosthetic group?
An essential part of a molecule, without which it could not function.
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Which ion does each haem group contain and why is this important?
Each haem group contains an iron ion (Fe2+), which can bind with one oxygen molecule - this is important for transporting oxygen around the blood.
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What is a protein associated with this kind (non-protein) group called?
A conjugated protein.
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What aesthetic property is the haem group also responsible for?
The colour of haemoglobin - when the oxygen molecule binds, the colour turns from purple to bright red.
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What is the molecule Insulin made of?
Two polypeptide chains.
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What is important about the A chain of insulin?
It begins with an alpha-helix.
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What is important about the B chain of insulin?
It ends with a beta-pleated sheet.
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What happens to both chains in the structure of the molecule?
They both fold into a tertiary structure.
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What joins the two chains of insulin together?
Disulphide links..
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What is on the outside of an insulin molecule?
Amino acids with hydrophilic R groups.
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Why are the hydrophilic amino acids in insulin important?
They make it soluble in water.
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How does insulin bind to muscle and fat cells?
Insulin bonds to the glycoprotein receptors on the outside of muscle and fat cells.
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Why does insulin bind to muscle and fat cells?
To increase their uptake of glucose from the blood, and to increase their rate of consumption of glucose.
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What is pepsin?
An enzyme that digests protein in the stomach.
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What does a pepsin molecule consist of?
A single polypeptide chain with 327 amino acids.
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What is special about the tertiary structure of pepsin?
It folds into a symmetrical shape.
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How many amino acids with basic R groups does pepsin have?
4
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How many amino acids with acidic R groups does pepsin have?
43.
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Why is having so many amino acids with acidic R groups useful to pepsin?
To help it survive in the acidic environment of the stomach. There are few basic groups to accept H+ ions and so there can be little effect on the enzyme's structure.
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How is the tertiary structure of pepsin held together?
By hydrogen bonds and two disulphide bridges.
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Being able to predict what can be incredibly useful in biochemistry?
Being able to predict the shape of a protein molecule from its primary structure.
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Being able to predict the occurence of biologically active binding sites on proteins can help with what?
Finding new medicines.
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How can scientists predict protein shapes?
Computer modelling techniques.
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What were techniqued for prediction of secondary structure based on?
The probability of an amino acid, or a sequence of amino acids, being in a particular secondary structure.
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How were the probabilities of an amino acid or sequence of amino aicds being in a secondary structure derived?
They were derived from 'already-known' protein molecular structures.
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What are 'Ab initio' protein modelling and comparative protein modelling used for?
Prediction of a molecule's tertiary structure?
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In Ab initio protein modelling, which two properties of atoms are modelled?
The physical and electrical properties of the atoms.
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In Ab initio protein modelling, which atoms have their properties modelled?
The atoms in each amino acid in the sequence.
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What is a drawback to Ab initio protein modelling?
There can be multiple solutions to the same amino acid sequence.
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What can be done to solve the problem with Ab initio protein modelling?
Other methods can be applied to reduce the number of solutions.
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What is the method for Comparative protein modelling?
Scanning of the amino acid sequence against a database of solved structures. This produces a set of possible models that would match the sequence.
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Card 2

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Are fibrous proteins soluble in water or insoluble?

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Insoluble.

Card 3

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Why would the structure of amino acids and insolubility be a good thing?

Back

Preview of the front of card 3

Card 4

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What shape do globular proteins take?

Back

Preview of the front of card 4

Card 5

Front

Why do globular proteins roll into a spherical shape?

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