Biology Phospholids-Proteins
3.10 - Phospholids and steroids are important lipids with a variety of functions
Phospholids are the major component of cell membranes
Composed of 1 glycerol, 2 fatty acids, and a phosphate group
The phosphate “head” is polar but the fatty acid “tails” are not
Steroids are lipids in which the carbon skeleton contains four fused rings with varying functional groups
Cholesterol is a common component in animal cell membranes and is used for making other steroids like sex hormones
3.12 - Proteins have a wide range of functions and structures
proteins are polymers made from amino acid monomers
proteins contain C, H, O, N
Most important function of proteins is to act as enzymes
Other proteins can help transport other molecules, aid in defense, act as signs, serve as cell receptor, aid movement via contraction, store amino acids
In general, proteins are needed for building and repairing tissues
Protein function is directly related to its 3D shape
Proteins can be globular or fibrous in shape
If a proteins structure is unraveled, denaturation occurs
denaturation can be caused by high heat, wrong pH, and wrong salinity
3.13 - Proteins are made from amino acids linked by peptide bonds
Amino acid structure
NH2
COOH
H
Central C
“R” group
R groups vary and give amino acid its properties
20 amino acids exist
2 amino acids join via covalent bond called a peptide bond
Dipeptide involves 2 amino acids; many form a polypeptide
3.14 - A protein’s functional shape results from four levels of structure
Primary structure
Precise sequence of amino acids in the polypeptide chai
determined by a genetic code
Secondary structure
Folding or pleating of the primary structure
Maintained by hydrogen bonds between atoms of polypeptide backbone
Tertiary Structure
Overall 3D shape of a protein
Caused by interaction of R groups
Results in globs or fibers
Quaternary structure
Proteins with more than one polypeptide chain