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Bio 151: Exam 2: Ch. 3
Terms in this set (10)
A living cell must manufacture proteins in order to survive. Summarize the four main concepts that we will learn about proteins in this chapter.
1. The tremendous diversity of protein structure and function arises from simple polymers of amino acids.
2. Proteins are dynamic structures that change shape: the spatial arrangements have been organized into categories, numbered 1 through 4 in increasing complexity.
3. proteins are only useful to cells if they change shape in predictable ways: two general ways for inducing these shapes.
4. Proteins have a limited lifetime: what happens to proteins when they wear out?
What is a polypeptide?
Long chain of amino acids: linear polymers made up of 20 different amino acids
What are the four parts of an amino acid?
1. Central carbon (with a hydrogen atom attached)
2. Amino group
3. Carboxyl group
4. A side chain (R or R group)
On what basis are the 20 amino acids classified, and what are the 3 main groups of amino acids?
-According to the chemical nature of their side chains
1. Non-polar (hydrophobic)
3. Ionic ( acidic and amine or imine)
Explain what is meant by structural polarity of an amino acid and name the ends of the protein polymer.
Every amino acid, whether it is part of a peptide bond or not, always has an amino group and carboxylic acid group attached to the alpha carbon: the functional groups are attached to opposite-facing bonds formed by the alpha carbon: if several amino acids are linked together by peptide bonds, each of them maintains this polarity: these two ends are called the amino terminus and carboxy terminus.
How many amino acids are in each of the following structures?
a). dipeptide______ b). tripeptide______ c). tetrapeptide______
2, 3, 4
When scientists stop counting the number of amino acids; they use this word to designate a few amino acids held together by peptide bonds.
"Protein" and "polypeptide" are not interchangeable terms. Why not?
Because polypeptide is typically 10 amino acids or more, but a protein is in most cases a single polypeptide. The term protein applies only to the collection of all the subunits when they become functional.
Define the following terms: subunit, monomer, dimer, polymer.
Subunit: When a protein is composed of 2 or more polypeptides
Monomer: a protein containing a single polypeptide
Dimer: a protein containing two subunits
Polymer: made from joining many monomers together
Summarize the three important traits of a protein.
1. All proteins adopt at least 2 stable 3-dimensional shapes.
2. All proteins bind to at least one molecular target.
3. All proteins perform at least one cellular function.
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