L.2 - proteins Flashcards
What determines what a cell looks like & how it functions?
- proteins
What is the function of the enzyme protein?
Catalyze specific chemical rxns
What is the function of the structural protein?
- strengthen and protect cells and tissues
What is the function of the storage protein?
Store nutrients
What is the function of the regulatory protein?
Control the activities of proteins, genes, cells, and tissues
What is the function of the motile proteins protein?
Generate movement in cells and tissues
What is the function of the protective protein?
Defend against foreign invaders
What are amino acids?
- the building blocks of protein
What is the main structure of amino acids??
- central carbon and hydrogen
- an amino functional group (NH2)
- a carboxylic acid/or carbonyls tree functional group (OH-C=O)
- a side chain known as the r group
How many different amino acids are there and what groups are they put in?
- 20 amino acids
- placed in either polar, nonpolar, or electrically charged groups
What are the 4 levels of protein organization?
- Primary - amino acid sequence
- Secondary - results from hydrogen bonding btw amino acids
- Tertiary - depends on interactions among side chains
- Quaternary - results from interactions among polypeptides
What is a peptide bond?
- a bond between the 2 amino acids.
How does a peptide form?
- form as a dehydration synthesis.
- create a peptide bond between the carboxylic acid group of 1 amino acid and the amino group of another.
- this will form a dipeptide bond
- the now free n-terminal and c-term old dipeptides are available to react with further amino acids to make larger polypeptides and eventually proteins
How strong are petite bonds?
- they are rigid but the adjacent R groups etc can rotate
What are the 2 structures of the ‘secondary structure’ of the formation of a protein?
- a-helix - hydrogen bonds hold the helix coils in shape
- b sheet - hydrogen bonds hold neighbouring strands of sheet together
Explain the alpha - helix .
- Each hydrogen bond forms between an oxygen with a partial negative charge and a hydrogen with a partial positive charge.
- The oxygen is part of the remains of the carboxyl group of one amino acid. The hydrogen is part of the remnant of the amino group of the fourth amino acid down the chain.
- Thus, 3.6 amino acids are included in each complete turn of the helix
- Basic structural unit of some fibrous proteins that make up all, hair, skin, and nails.
- Elasticity due to the helical shape and hydrogen bonding.
Explain beta pleated sheet.
- the hydrogen bonding takes place between different polypeptide chains or different regions of a polypeptide chain that has turned back in itself
- each chain is fully extended as each has a zigzag structure
- the resulting sheet has an overall pleated confirmation
- strong and flexible but not elastic as the distance between the pleats is fixed
- fibroin, the protein of silk
What holds the tertiary structure together?
- hydrogen bond
- ionic bond
- hydrophobic interactions
- disulfied bridges btw R groups
Describe the tertiary structure.
When a-helical regions and b-pleated sheets come together and interact and form the overall conformation of the tertiary structure
Describe the quaternary structure.
When you have more than 1 polypeptide.
2 alpha chains and 2 beta chains (a-goblin & b-goblin)
Why do proteins have different conformations?
- confirmation is dictated by the amino acid sequence
- by environments - conditions in a cell in vivid may be different than outside ex. Test tube or ex-Vivo
- specialized proteins - molecular chaperones
What assists proteins in folding?
- molecular chaperones
What are the 3 main classes of molecular chaperones?
- Hsp60 (chaperones)
- Hsp70
- Hsp90
What does Hsp70 do? (Look at diagram !!)
- recognizes exposed, unfolded regions of new protein chains - especially hydrophobic regions
- it binds to these regions, protecting them until productive folding reactions can occur
What determines the role of the protein?
- it’s structure
Different regions of a protein can have…
Different functions
Are proteins modular?
- many are
- 2 or more globular regions - domains connected by less compact regions of polypeptide chain
- in then, each domain can have different functions since as one domain can clash as an enzyme while the other docks in a membrane
What is denaturation? What does it do? What causes it?
- caused by change in environment (heat, ph change, chemical exposure)
- it is a condition that affect protein function
- it disrupts hydrogen and ionic bonding
- leads to unfolding, change in shape
- loss of biological activity
Describe enzyme activation?
- Step one: a pair of substrate molecules bind to the active site.
- Step two: the substrate interact, forming product.
- Step three: that product detaches from the active site. Because the structure of the enzyme has not been affected, the entire process can be repeated.
How important are enzymes?
- all chemical rxns in living organisms require enzymes to work
- they are building molecules - synthesis enzymes
- breakdown molecules - digestive enzymes
- enzymes speed up rxns - catalysts
Each enzyme need to be the right ___ for the job
- shape
Enzymes are named for the rxns they help. Name some.
- sucrose breaks down sucrose
- proteases break down proteins
- lipases break down lipids
- DNA polymerase builds DNA
Are enzymes changed by the rxn?
- no
- they are only used temporarily
- reused again for the same rxn w/ other molecules
- very little enzyme needed to help in many rxns
Lock & key model - explain it.
- shape of protein allows enzyme & substrate to fit
- specific enzyme for each specific rxn
