1. Chapter 3 Part 2 Lecture Outline See PowerPoint Image Slides
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2. Proteins Proteins are polymers made of amino acids.
An amino acid contains:
Central carbon
Amino group
Carboxyl group
Hydrogen
There are 20 different amino acids.
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3. The Structure of Proteins
Amino acids are joined via dehydration synthesis.
The bond formed between amino acids is called a peptide bond.
Several amino acids joined together form polypeptide chains.
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4. Primary Structure
The sequence of amino acids in a polypeptide constitutes the primary structure of the protein.
This sequence is dictated by information in genes (DNA).
All levels of protein structure depend on the primary sequence.
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5. Secondary Structure
Polypeptides twist and fold into their secondary structure.
Some sequences of amino acids twist into a helix.
This is called an alpha helix.
Some sequences of amino acids remain straight and fold back on themselves.
This is called a beta-pleated sheet.
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6. Tertiary Structure
The various alpha helices and beta pleated sheets interact to form a globular structure.
This globular structure is unique for each polypeptide.
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7. Quaternary Structure
Some proteins contain more than one polypeptide chain.
Each of these polypeptides has its own unique tertiary structure.
These polypeptides interact to form a more complex globular structure.
Quaternary structure can be stabilized by disulfide bonds.
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8. Form and Function The protein’s overall shape determines its job.
If a protein is not shaped properly, it likely will not work properly.
Example:
Sickle cell anemia
A mutation in the gene causes the protein to have a different shape.
This shape change results in a change in function.
Denaturation:
When heat or other environmental conditions break the bonds that stabilize tertiary structure.
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9. Types of Proteins Structural proteins Regulatory proteins
Important in maintaining the shape of cells and organisms
Collagen
Regulatory proteins
Determine what activities will occur in a protein
Enzymes and hormones
Carrier proteins
Transport molecules from one place to another
Lipoproteins
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10. Nucleic Acids The largest biological molecules
Store and transfer information within a cell
Include DNA and RNA
Are made of nucleotides
5-carbon sugar
Phosphate group
Nitrogenous group
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11. Nucleotides
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12. DNA Each DNA molecule is made of two strands.
Held together by hydrogen bonds between the nitrogenous bases
The bases pair according to base pair rules.
Adenine - thymine
Cytosine - guanine
The two DNA strands are twisted on each other, forming a double helix.
Each DNA strand is divided into segments.
Each segment forms a gene.
Genes are the recipes for proteins.
The sequence of nucleotides in a gene dictate the order of amino acids in a polypeptide.
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13. The Structure of DNA
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14. DNA and Chromosomes Each DNA strand has many genes.
Each DNA strand is called a chromosome.
Human cells have 46 chromosomes in each cell.
Each cell copies all of these chromosomes before it divides to pass along to daughter cells.
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15. The Functions of DNA DNA is able to: Replicate itself
Store information and transmit it to offspring
Direct synthesis of proteins
Mutate (change chemically)
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16. The Functions of DNA
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17. RNA RNA is a single-stranded molecule.
Contains uracil instead of thymine
Base pairs with itself and DNA
A-U
G-C
RNA is found in three different forms:
mRNA (messenger RNA)
rRNA (ribosomal RNA)
tRNA (transfer RNA)
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18. DNA vs. RNA
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19. Lipids Commonly called fats Large and nonpolar
Do not dissolve in water
Dissolve in other nonpolar molecules like acetone
Usually have very few oxygen atoms
There are three main types of lipids:
True fats (e.g., pork chop fat and oils)
Phospholipids (membrane components)
Steroids (most hormones)
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20. True (neutral) Fats Used to provide energy The building blocks of fats
A glycerol molecule
Three fatty acids
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21. Saturated vs. Unsaturated Lipids
If the carbon skeleton of a fatty acid has as much hydrogen as possible, the fat is called a saturated fat.
Saturated fats are found in animal tissues and tend to be solid at room temperature.
If the carbons of a fat have double-bonded carbon molecules in them, the fat is called unsaturated fat.
Unsaturated fats are frequently plant fats and are liquids at room temperature.
A polyunsaturated fat has several double bonds.
Fats are important energy storage molecules.
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22. Saturated and Unsaturated Fatty Acids
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23. Phospholipids
Are complex organic molecules that resemble fats but contain phosphate groups
Phospholipids are the major components of cell membranes.
Some are known as lecithins.
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24. Steroids Nonpolar molecules that are arranged in rings of carbon
Steroids are important components of cell membranes.
Cholesterol
Steroids often serve as hormones and serve in regulation of body processes.
Testosterone, estrogen
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25. Overview
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