2 Proteins Proteins are polymers made of monomers called amino acids All proteins are made of 20 different amino acids linked in different orders Proteins are used to build cells act as hormones amp enzymes and do much of the work in a cell ID: 226892
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ProteinsSlide2
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Proteins
Proteins are polymers made of monomers called amino acids
All proteins are made of 20 different amino acids linked in different orders
Proteins are used to build cells, act as hormones & enzymes, and do much of the work in a cellSlide3
copyright cmassengale
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Structure of Amino Acids
Amino acids have a central carbon with 4 things boded to it:
Amino group –NH
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Carboxyl group -COOH
Hydrogen -H
Variable group -R
Amino
group
Carboxyl
group
R group
Side groups
Leucine -hydrophobic
Serine-hydrophillicSlide5
5
20 Amino Acid Monomers-these are the R groups Slide6
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Linking Amino Acids
Cells link amino acids together to make proteins
The process is called dehydration synthesis
Peptide
bonds form to hold the amino acids together
Carboxyl
Amino
R Group
Dehydration Synthesis
Peptide BondSlide7
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Proteins (Polypeptides)
Four levels of protein structure:
A. Primary Structure
B. Secondary Structure
C. Tertiary Structure D. Quaternary Structure Slide8
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Protein Structures or CONFORMATIONS
Hydrogen bond
Pleated sheet
Amino acid
(a) Primary structure
Hydrogen bond
Alpha helix
(b) Secondary structure
Polypeptide
(single subunit)
(c) Tertiary structure
(d) Quaternary structureSlide9
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Primary Structure
Amino acids
bonded together by
peptide bonds (straight chains)
aa1
aa2
aa3
aa4
aa5
aa6
Peptide Bonds
Amino Acids (aa)Slide10
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Primary Protein Structure
The
primary
structure is the specific sequence of amino acids in a protein
Called
polypeptide
Amino AcidSlide11
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Protein Structures
Secondary protein structures occur when protein chains
coil or fold
When protein chains called polypeptides join together, the
tertiary
structure forms because
R groups interact
with each other
In the watery environment of a cell, proteins become
globular
in their
quaternary
structureSlide12
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Secondary Structure
3-dimensional folding arrangement of a
primary structure
into
coils and pleats held together by hydrogen bonds.Two examples:
Alpha Helix
Beta Pleated Sheet
Hydrogen BondsSlide13
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Tertiary Structure
Secondary structures
bent
and folded into a more complex 3-D arrangement of linked polypeptidesBonds: H-bonds, ionic, disulfide bridges (S-S)Call a “subunit”.
Alpha Helix
Beta Pleated SheetSlide14
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Quaternary Structure
Composed of 2 or more
“subunits”
Globular in shape
Form in Aqueous environmentsExample: enzymes (hemoglobin)subunitsSlide15
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Changing Amino Acid Sequence
Substitution of one amino acid for another in hemoglobin causes sickle-cell disease
(a) Normal red blood cell
Normal hemoglobin
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2
3
4
5
6
7. . . 146
(b) Sickled red blood cell
Sickle-cell hemoglobin
2
3
1
4
5
6
7. . . 146Slide16
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Other Important Proteins
Blood sugar level is controlled by a protein called
insulin
Insulin causes the liver to uptake and
store excess sugar as GlycogenThe cell membrane also contains proteinsReceptor proteins help cells recognize other cellsSlide17
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INSULIN
Cell membrane with proteins & phospholipidsSlide18
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Nucleic AcidsSlide19
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Nucleic acids
Nucleic acids
are composed of long chains of
nucleotides
linked by dehydration synthesis.Function: Dictate amino acid sequences/how proteins are madeSource of all genetic informationTwo types:
a. Deoxyribonucleic acid (DNA)
b. Ribonucleic acid (RNA)Slide20
20Slide21
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Nucleotide-monomer/building block of nucleic acid
s
O
O=P-O
OPhosphate Group
N
Nitrogenous base
(A, G, C, or T)
CH2
O
C
1
C
4
C
3
C
2
5
Sugar
(deoxyribose)Slide22
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Another look at a Nucleotide – Nucleic acid monomerSlide23
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Nucleic Acids
Nitrogenous base
(A,G,C, or T)
Phosphate
group
Thymine (T)
Sugar
(deoxyribose)
Phosphate
Base
Suga
r
Nucleic acids are polymers of nucleotides
NucleotideSlide24
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Nucleic acids
Nucleotides include:
phosphate group
pentose sugar (5-carbon) nitrogen bases:
adenine (A)
thymine (T) DNA only
uracil
(U) RNA only
cytosine (C)
guanine (G)Slide25
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Bases
Each DNA nucleotide has one of the following bases:
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Adenine (A)
Guanine (G)
Thymine (T)
Cytosine (C)Slide26
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DNA
Two strands of DNA join together to form a double helix
Base
pair
Double helixSlide27
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DNA - double helix
P
P
P
O
O
O
1
2
3
4
5
5
3
3
5
P
P
P
O
O
O
1
2
3
4
5
5
3
5
3
G
C
T
ASlide28
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RNA – Ribonucleic Acid
Ribose sugar has an extra –OH or hydroxyl group
It has the base uracil (U) instead of thymine (T)
Nitrogenous base
(A,G,C, or U)
Sugar (ribose)
Phosphate
group
UracilSlide29
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ATP – Cellular Energy
ATP
is used by cells for
energy
Adenosine triphosphateMade of a nucleotide with 3 phosphate groupsSlide30
The Chemistry of LifeOrganic Compounds LabSlide31
Indicator A substance used to show the presence of another substance Color change = positive test (the substance is present)Slide32
Distilled WaterUse it as a control – to make sure the indicators are working.No color change with water = indicators are working Slide33
Lipid Test Sudan III stain – red is a positive testBrown paper bag – Lipids leave translucent spots (grease spots)Slide34
Carbohydrate Test Starch – Iodine- blue/black is a positive testSugar – Benedict’s solution – **MUST BE HEATED!!!!*blue/green changes to orange/yellow = positive test Slide35
Protein Test Biuret reagent - varying shades of purple = positive test