Proteins Flashcards
What do proteins have in all living organisms?
A huge variety of functions.
What are the monomers of proteins?
Amino acids.
What is made when two amino acids join together?
A dipeptide.
What is formed when more than two amino acids join together?
A polypeptide.
What are proteins made up of?
One or more polypeptide
What does a monomer of proteins look like?
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What does a dipeptide look like?
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What does a polypeptide look like?
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What do proteins look like?
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What are proteins regarding amino acids?
They are polymers of them.
What do all amino acids have?
The same general structure.
What is the same general structure that all amino acids have?
- A carboxyl group (-COOH).
- An amino group (-NH2).
- And an R group attached to a carbon atom (A variable side group).
What do R groups contain?
Carbon.
What is the only exception to the rule that R groups contain carbon?
Glycine, which has an R group of just one hydrogen atom.
What does the general structure of amino acids look like?
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How many amino acids do all living things share?
A bank of 20 amino acids.
What’s the only difference between the bank of amino acids that all living things share?
What makes up their R group.
How are amino acids joined together?
By condensation reactions.
What happens during the formation of dipeptides and polypeptides?
A condensation reaction, wherein a molecule of water is released as the bonds are formed.
What bond forms between amino acids?
Peptide bonds.
What is the reverse reaction of the formation of dipeptides and polypeptides?
Hydrolysis (breaking down).
What does the reversible reaction of the forming and breaking down of dipeptides look like?
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What are the structures like in proteins?
They are big complicated molecules, with four levels of structures.
What are the four levels of protein structures?
- Primary structure
- Secondary structure
- Tertiary structure
- Quaternary structure
What is the primary structure of proteins?
The sequence of amino acids in the polypeptide chain.
What does the primary structure of proteins look like?
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How does the primary structure of proteins change to the secondary structure of proteins?
The polypeptide chain is no longer flat and straight because hydrogen bonds form between the amino acids in the chain, causing it to automatically coil.
What can the polypeptide chain coil into in the secondary structure of proteins?
- Alpha () helix
* Beta () pleated sheet
What are hydrogen bonds?
A relatively weak bond formed between hydrogen atoms and other atoms.
What does the alpha helix secondary structure look like?
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How does the secondary structure of proteins change to the tertiary structure of proteins?
The chain of amino acids is often coiled or folded further and more bonds form between different parts of the polypeptide chain, including hydrogen bonds and ionic bonds. Disulfide bridges also form.
What are the ionic bonds in the tertiary structure of proteins?
Attractions between negative and positive charges on different parts of the molecule.
How do disulfide bridges form in the tertiary structure of proteins?
Whenever two molecules of the amino acid cysteine come close together (the sulfur atom in one cysteine bonds to the sulfur atom in the other).
What happens in the tertiary structure for proteins made of a single polypeptide chain?
The tertiary structure forms their final 3D structure.
What are disulfide bridges?
Covalent bonds between sulfur atoms.
What are disulfide bridges compared to hydrogen and ionic bonds?
They are a lot stronger.
What does the tertiary structure of proteins look like?
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How does the tertiary structure of proteins change to the quaternary structure of proteins?
Some proteins are made of several different polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together.
What is the quaternary structure for proteins made from more than one polypeptide chain?
The protein’s final 3D structure.
What does the quaternary structure of proteins look like?
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What does a protein’s shape determine?
It’s function.
What is an example of a protein’s shape determining its function?
Haemoglobin is a compact, soluble protein, which makes it easy to transport. This makes it great at carrying oxygen around the body.
How are proteins specialised?
They’ve all got different structures and shapes.
What are proteins specialised for?
To carry out particular jobs.
What protein’s shapes/structures and functions do you need to know?
- Enzymes
- Antibodies
- Transport proteins (channel proteins)
- Structural proteins
What is the shape of an enzyme?
They’re usually roughly spherical in shape.
Why are enzymes usually roughly spherical in shape?
Due to the tight folding of the polypeptide chains.
What functions do enzymes have?
- Roles in metabolism
- Breaking down large food molecules
- Synthesising large molecules
What is the shape of an antibody?
They’re made up of two light (short) polypeptide chains and two heavy (long) polypeptide chains bonded together.
What are the functions of antibodies?
They are involved in the immune response.
Where are antibodies found?
In the blood.
What do antibodies have?
Variable regions (the amino acid sequences in these regions vary greatly).
What is the shape of a transport protein?
Channel proteins contain hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel.
What is the function of a transport protein
They transport molecules and ions across membranes.
Where are transport proteins located?
Cell membranes.
What do transport proteins look like?
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What is the shape of a structural protein?
They consist of long polypeptide chains lying in parallel to each other with cross-links between them.
What are structural proteins?
Physically strong.
What are some examples of structural proteins?
- Keratin (found in hair and nails)
* Collagen (found in connective tissue)
What is the shape of the structural protein collagen?
It has three polypeptide chains tightly coiled together, making it strong.
What is the function of the structural protein collagen?
It is a great supportive tissue in animals.
What does the structural protein collagen look like?
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How do you test for the presence of proteins in a sample?
By doing the biuret test for proteins.
What is the method of the biuret test for proteins?
- The test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution.
- The. You add copper(II) sulfate solution.
What are the results of the biuret test for proteins?
- If a protein is present, the solution turns purple.
* If there is no protein the solid on will stay blue.
What does the biuret test for proteins look like?
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