Proteins ()aminoacidsss presentations chapter 21.ppt

Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.

Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains. There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function. Amino acids are coded by combinations of three DNA building blocks (nucleotides), determined by the sequence of genes.

Proteins can be described according to their large range of functions in the body, listed in alphabetical order:

Examples of protein functions
Antibody

Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body.

Immunoglobulin G (IgG)

Enzyme

Enzymes carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA.

Phenylalanine hydroxylase

Messenger

Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs.

Growth hormone

Structural component

These proteins provide structure and support for cells. On a larger scale, they also allow the body to move.

Actin

Transport/storage

These proteins bind and carry atoms and small molecules within cells and throughout the body.

Ferritin
Proteins are very large molecules composed of basic units called amino acids. Proteins contain carbon, hydrogen, oxygen, nitrogen, and sulphur.

Protein molecules are large, complex molecules formed by one or more twisted and folded strands of amino acids. Proteins are highly complex molecules that are actively involved in the most basic and important aspects of life. These include metabolism, movement, defense, cellular communication, and molecular recognition.

Positive negative attractions between different atoms in the long amino acid strand cause it to coil on itself again and again to form its highly complex shape. Folded proteins may combine with other folded proteins to form even larger more complicated shapes.

The folded shape of a protein molecule determines its role in body chemistry. Structural proteins are shaped in ways that allow them to form essential structures of the body. Collagen, a protein with a fibre shape, holds most of the body tissues together. Keratin, another structural protein forms a network of waterproof fibres in the outer layer of the skin.

Functional proteins have shapes that enable them to participate in chemical processes of the body. Functional proteins include some of hormones, growth factors, cell membrane receptors, and enzymes.
Protein molecules are large, complex molecules formed by one or more twisted and folded strand

1. © 2010 Pearson Education, Inc.
Chapter 6: Proteins and
Amino Acids

2. © 2010 Pearson Education, Inc.
What Are Proteins?
Large molecules
Made up of chains of amino acids
Are found in every cell in the body
Are involved in most of the body’s functions and life
processes
The sequence of amino acids is determined by DNA

3. © 2010 Pearson Education, Inc.
Structure of Proteins
Made up of chains of amino acids; classified by number of
amino acids in a chain
•Peptides: fewer than 50 amino acids
-Dipeptides: 2 amino acids
-Tripeptides: 3 amino acids
-Polypeptides: more than 10 amino acids
•Proteins: more than 50 amino acids
-Typically 100 to 10,000 amino acids linked together
Chains are synthesizes based on specific bodily DNA
Amino acids are composed of carbon, hydrogen, oxygen,
and nitrogen

4. Structural Differences Between Carbohydrates,
Lipids, and Proteins
Figure 6.1

5. The Anatomy of an Amino Acid
Figure 6.2b

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Peptide Bonds Link Amino Acids
Form when the acid group (COOH) of one amino acid joins
with the amine group (NH
2) of a second amino acid
Formed through condensation
Broken through hydrolysis

7. Condensation and Hydrolytic Reactions
Figure 6.3

8. © 2010 Pearson Education, Inc.
Essential, Nonessential, and Conditional
Essential – must be consumed in the diet
Nonessential – can be synthesized in the body
Conditionally essential – cannot be synthesized due to
illness or lack of necessary precursors
•Premature infants lack sufficient enzymes needed to
create arginine

10. © 2010 Pearson Education, Inc.
Structure of the Protein
Four levels of structure
•Primary structure
•Secondary structure
•Tertiary structure
•Quaternary structure
Any alteration in the structure or sequencing changes
the shape and function of the protein

11. © 2010 Pearson Education, Inc.
Denaturing
Alteration of the protein’s shape and thus functions through
the use of
•Heat
•Acids
•Bases
•Salts
•Mechanical agitation
Primary structure is unchanged by denaturing

12. Denaturing a Protein
Figure 6.5

13. © 2010 Pearson Education, Inc.
Quick Review
Proteins are chains of combination of amino acids
Amino acids contain carbon, hydrogen, oxygen, nitrogen,
and sometimes sulfur
Unique amino acids consist of a central carbon with a
carboxyl group, a hydrogen, a nitrogen-containing amine
group, and a unique side chain
There are 20 side chains and 20 unique amino acids
•9 essential amino acids
•11 nonessential amino acids
-At time these become conditionally essential
Amino acids link together with peptide bonds by
condensation and break apart by hydrolysis

14. © 2010 Pearson Education, Inc.
Quick Review
Attractions and interactions between the side chains cause
the proteins to fold into precise three-dimensional shapes
Protein shape determines its function
Proteins are denatured and their shapes changed by
•Heat
•Acids
•Bases
•Salts
•Mechanical agitation