Organic molecules 3of4 (proteins)
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What are proteins made of?
- Large organic molecules that contain carbon, hydrogen, oxygen, and nitrogen. Some contain sulfur.
- Much more complex in structure than carbohydrates or lipids.
- Made of amino acids that form chains called polypeptides, that fold and bend to form proteins.
How do proteins work?
- Have MANY different roles in the body, largely responsible for most of the structure in body tissues.
- Have MANY different 3-D shapes that relate to their many functions.
- Proteins recognize and bind to other molecules such as antibodies to foreign substances.
- Their unique shape permits them to interact with other molecules to carry out specific functions.
What are some specific proteins and their functions?
- Enzymes- Speed up most biochemical reactions
- Antibodies- Defend against invading microbes
- Some hormones are proteins that regulate homeostasis
- Other proteins work as 'motors' to drive muscle contraction
What are the six types of proteins?
Describe structural proteins and give examples.
- Form structural framework of various parts of body.
- EX: Collagen in bone and other connective tissue
- EX: Keratin in skin, hair, and fingernails
Describe regulatory proteins and give examples.
- Function as hormones that regulate various physiological processes.
- Control growth and development.
- As neurotransmitters, mediate responses of nervous system.
- EX: Hormone insulin regulates blood glucose levels
- EX: Neurotransmitter substance P mediates sensation of pain in nervous system.
Describe contractile proteins and give examples.
- Allows shortening of muscle cells, which produces movement.
- EX: myosin, actin
Describe immunological proteins and give examples.
- Aid responses that protect body against foreign substances and invading pathogens.
- EX: Antibodies
- EX: Interleukins
Describe transport proteins and give examples.
- Carry vital substances throughout body
- EX: Hemoglobin (transport most oxygen and some carbon dioxide in blood)
Describe catalytic proteins and give examples.
- Act as enzymes that regulate biochemical reactions.
- EX: salivary amylase
- EX: sucrase
- EX: ATPase
What % of the body is protein on a lean adult?
What is an amino acid? How many are there?
- The monomers of proteins
- All consist of a H atom and 3 functional groups attached to an alpha carbon. Amino group (-NH2), acidic carboxyl group (-COOH), and an R group (side chain) that gives each its individual chemical identity.
What are the characteristics of the functional groups of an amino acid?
- The amino group (-NH2) and acidic carboxyl group (-COOH) form ions in regular blood pH. (-NH3^+) and (-COO^-)
- The R group gives each amino acid its distinctive chemical identity.
What is a peptide bond?
- A covalent bond between the C of an acidic carboxyl group (-COOH) and the N of an amino group (-NH2) in different amino acids.
- A dehydration synthesis reaction.
What is a dipeptide? Tripeptide?
- Dipeptide- Two amino acids covalently bonded (peptide bond).
- Tripeptide- Adding a third amino acid (another peptide bond) to the chain.
- This is a dehydration synthesis reaction.
What is a peptide?
A peptide chain of 4-9 amino acids
What is a polypeptide? How many are used to make proteins?
- A peptide chain containing 10-2000 or more amino acids in a chain.
- A small protein can have a single polypeptide with +/-50 amino acids, larger ones can have hundreds or thousands of amino acids and multiple polypeptide chains folded together.
What are the structural levels of organization of proteins?
- Primary structure
- Secondary structure
- _ _
- Tertiary structure (TUR-she-er'-e)
- Quaternary structure
Describe the first structural level of organization of proteins. Name it as well.
- Primary structure.
- The linear sequence of amino acids in the polypeptide.
- Primary structure is genetically determined, changes in amino acid sequence can have serious effects on body cells.
Describe the second structural level of organization of proteins. Name it as well.
- Secondary structure (3 dimensional shape of polypeptide)
- Consists of alpha helixes-- helixes formed from hydrogen bonds (BETWEEN THE BACKBONES, not r groups) in the polypeptide.
- As well as beta sheets-- side by side rows or columns of amino acids that are zigzagged (think crinkle cut fries); can be parallel with multiple polypeptides (amino acids parallel to the same aa) or antiparallel where there is only one polypeptide and the amino acids are not parallel to the same kind of aa.
Describe the third structural level of organization of proteins. Name it as well.
- Tertiary structure (Higher order of folding)
- Distant folding between the (ONLY ONE) polypeptide after the secondary structures are formed. (OVERALL 3-D structure)
- Hydrogen bonds (BETWEEN R GROUPS), ionic bonds, hydrophobic/philic interactions, disulfide bridges effect this shape.
- Helper molecules called chaperones aid the folding process.
What are disulfide bridges? (S-S)
- Strongest but least common bond in polypeptides. Between R groups in cysteins so related to tertiary structure.
- Covalent bonds that hold together some of the tertiary structure of proteins.
- Form between the sulfhydryl groups (-SH) of two monomers of the amino acid cysteine
Describe the fourth structural level of organization of proteins. Name it as well.
- Quaternary Quaternary
- The arrangement of two or more polypeptides (sub units) to form a protein (complete unit).
- The interactions between the chains are not different from those in tertiary structure, but are distinguished only by being interchain rather than intrachain. (inter- between or among, intra- within)
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