Download proteins - Biology Fall Semester

PROTEINS
Objective:
• Compare the structure and functions of lipids,
proteins.
Warm Up:
What foods do you eat that contain lipids (fats) or
proteins?
– List two sources of lipids and two sources of proteins.
Today’s Plan
• Warm up
• Real world reading
• Review lipids
• Review protein notes
• Create a Model
• Draw the Macromolecules
• Closing
Lipids
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Lipids are a large and varied group of biological molecules. Lipids
are made mostly from carbon and hydrogen atoms and are generally
not soluble in water.
The common categories of lipids are fats, oils, and waxes.
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Lipids can be used to store energy. Some lipids are important parts
of biological membranes and waterproof coverings.
•
Steroids synthesized by the body are lipids as well. Many steroids,
such as hormones, serve as chemical messengers.
Lipids
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Many lipids are formed when a glycerol molecule combines with
compounds called fatty acids.
Lipids
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If each carbon atom in a lipid’s fatty acid chains is joined to another
carbon atom by a single bond, the lipid is said to be saturated.
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If there is at least one carbon-carbon double bond in a fatty acid, the
fatty acid is said to be unsaturated.
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Lipids whose fatty acids contain more than one double bond are said
to be polyunsaturated.
Lipids
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Lipids that contain unsaturated fatty acids, such as olive oil, tend to
be liquid at room temperature.
•
The data in the table illustrate how melting point decreases as the
degree of unsaturation (number of double bonds) increases.
Amino Acid
• Amine group acts like a base, tends to be positive.
• Carboxyl group acts like an acid, tends to be negative.
• “R” group is variable, from 1 atom to 20.
• Two amino acids join together to form a dipeptide.
• Adjacent carboxyl and amino groups bond together.
Characteristics of Proteins
• Contain carbon, hydrogen, oxygen,
nitrogen, and sulfur
• Serve as structural components of
animals
• Serve as control molecules (enzymes)
• Serve as transport and messenger
molecules
• Basic building block is the amino acid
Some Amino Acids
Some More Amino
Acids
Still More Amino Acids
Formation of a Dipeptide
Dehydration synthesis
Amino Acid + Amino Acid --> Dipeptide
Amino Acid + Dipeptide --> Tripeptide
A.A. + A.A. + …..+ Tripeptide -->
Polypeptide
A protein consists of one or more
polypeptide chains.
Protein
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Proteins are macromolecules that contain nitrogen as well as
carbon, hydrogen, and oxygen.
Proteins are polymers of molecules called amino acids.
Proteins perform many varied functions, such as controlling the rate
of reactions and regulating cell processes, forming cellular structures,
transporting substances into or out of cells, and helping to fight
disease.
Protein
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Amino acids are compounds with an amino group (–NH2) on one
end and a carboxyl group (–COOH) on the other end.
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Covalent bonds called peptide bonds link amino acids together to
form a polypeptide.
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A protein is a functional molecule built from one or more
polypeptides.
Structure and Function
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All amino acids are identical in the amino and carboxyl groups. Any
amino acid can be joined to any other amino acid by a peptide bond
formed between these amino and carboxyl groups.
Structure and Function
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•
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Amino acids differ from each other in a side chain called the R-group,
which have a range of different properties.
More than 20 different amino acids are found in nature.
This variety results in proteins being among the most diverse
macromolecules.
Levels of Organization
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Proteins have four levels of structure.
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A protein’s primary structure is the
sequence of its amino acids.
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Secondary structure is the folding or
coiling of the polypeptide chain.
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Levels of Organization
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Tertiary structure is the complete, threedimensional arrangement of a polypeptide
chain.
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Proteins with more than one chain have a
fourth level of structure, which describes
the way in which the different polypeptide
chains are arranged with respect to each
other. For example, the protein shown,
hemoglobin, consists of four subunits.
Objective:
• Compare the structure and functions of lipids,
proteins and carbohydrates.
Closing:
Summarize the difference between carbs, proteins and lipids or
answer the following:
A scientist removed the cell membranes from bacteria cells in a culture.
She analyzed the cell membranes for specific molecules.
Which of these was probably the most common type of molecule
present in the bacteria cell membranes?
A. lipid
B. amino acid
C. nucleic acid
D. carbohydrate