Unit 1 (Chapter 3 Part 4) Proteins Flashcards
What is a functional unit composed of one or more polypeptides? Each polypeptide is composed of a linear sequence of amino acids.
Proteins.
Accounts for 50% of the organic material in a typical animal’s body,
Comes from the Greek word, proteios, meaning first rank.
What are the different categories of major proteins? (7)
- Proteins involved in gene expression and regulation
- Motor proteins
- Defense proteins
- Metabolic enzymes
- Cell-signaling proteins
- Structural proteins
- Transporters
What elements are proteins composed of?
Carbon, hydrogen, oxygen, nitrogen, and small amounts of sulfur.
What are the monomers of proteins?
Amino Acids
Any of the monomers that are linked to form a protein. Amino acids have a common structure in which a carbon atom, called the α-carbon, is linked to an amino group (─NH2) and a carboxyl group (─COOH), as well as to a hydrogen atom and a side chain that distinguishes the particular amino acid.
When an amino acid is dissolved in water, what happens to its functional groups?
The amino group, -NH2, accepts a positively charged hydrogen ion or cation.
Whereas the carboxyl group, loses a hydrogen ion, and becomes negatively charged.
THIS is why the name amino acid was given to such molecules because their amino and carboxyl group acts like an acid.
All amino acids have isomeric forms except what protein?
Glycine.
What are the isomeric forms of proteins?
D and L forms.
They are enantiomers. Remember: enantiomers are mirror images of each other.
What amino acid enantiomers are found in proteins?
L-amino acids
Where can the enantiomers, D-amino acids, be found in nature?
In the cell walls of bacteria, where they play a protective role against molecules secreted by the host organism in which the bacteria live.
How are amino acids distinguished?
By their side chains.
How are amino acids categorized?
Whether or not their side chains are nonpolar, polar and uncharged, or polar and charged.
What is critical in how side chains of proteins function?
Their structure.
How are amino acids joined together in which the carboxyl group of one amino acid to the amino group of another?
Dehydration reaction
What do you call the covalent bond between a carboxyl and amino group that links amino acids in a polypeptide?
A peptide bond.
What is a molecule consisting of a linear sequence of amino acids; the term denotes structure?
Polypeptide
What do you call the amino and carboxyl ends on a polypeptide?
The N-terminus and C-terminus.
The C-terminus has a free carboxyl group while the other end is a free amino group.
How many water molecules would be produced during the formation of a polypeptide that is 72 amino acids long?
71; one less than the total number of amino acids in a polypeptide (linear sequence of amino acids).
What is a FUNCTIONAL unit composed of one or more polypeptides?
A protein which has folded and twisted into a precise-three dimensional shape.
Each polypeptide is composed of a linear sequence of amino acids.
What are proteins called when they have carbohydrates or lipids attached to them changing their function?
Glycoproteins and Lipoproteins.
These modifications impart unique functions to such proteins.
What are the different levels of a protein as in hierarchy?
Primary, secondary, tertiary, and quaternary.
Each higher level of structure depends on the preceding level. If the primary structure is changed, it may as well have an affect on the subsequent levels.
What is considered the primary structure of a protein?
The linear sequence of amino acids of a polypeptide(s).
How are the primary structures of a protein determined?
Genes and their expressions.
What does the secondary structure of a protein? (2) basic forms
The bending or twisting of a region of a protein into an (a helix) or (b sheet).
How is the polypeptide backbone of the helix structure stabilized? What about the plated sheet?
Hydrogen bonds.
The hydrogen atoms linked to a nitrogen atom forms a bond with oxygen atom that is double bonded to a carbon atom. These occur at regular intervals.
Same with the pleated sheet, but the polypeptide backbone runs parallel with each with hydrogen bonds between them.