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By the end of this section, you will be able to:
  • Describe the functions proteins perform in the cell and in tissues
  • Discuss the relationship between amino acids and proteins
  • Explain the four levels of protein organization
  • Describe the ways in which protein shape and function are linked

Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective; they may serve in transport, storage, or membranes; or they may be toxins or enzymes. Each cell in a living system may contain thousands of proteins, each with a unique function. Their structures, like their functions, vary greatly. They are all, however, polymers of amino acids, arranged in a linear sequence.

Types and functions of proteins

Enzymes , which are produced by living cells, are catalysts in biochemical reactions (like digestion) and are usually complex or conjugated proteins. Each enzyme is specific for the substrate (a reactant that binds to an enzyme) it acts on. The enzyme may help in breakdown, rearrangement, or synthesis reactions. Enzymes that break down their substrates are called catabolic enzymes, enzymes that build more complex molecules from their substrates are called anabolic enzymes, and enzymes that affect the rate of reaction are called catalytic enzymes. It should be noted that all enzymes increase the rate of reaction and, therefore, are considered to be organic catalysts. An example of an enzyme is salivary amylase, which hydrolyzes its substrate amylose, a component of starch.

Hormones are chemical-signaling molecules, usually small proteins or steroids, secreted by endocrine cells that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction. For example, insulin is a protein hormone that helps to regulate the blood glucose level. The primary types and functions of proteins are listed in [link] .

Protein Types and Functions
Type Examples Functions
Digestive Enzymes Amylase, lipase, pepsin, trypsin Help in digestion of food by catabolizing nutrients into monomeric units
Transport Hemoglobin, albumin Carry substances in the blood or lymph throughout the body
Structural Actin, tubulin, keratin Construct different structures, like the cytoskeleton
Hormones Insulin, thyroxine Coordinate the activity of different body systems
Defense Immunoglobulins Protect the body from foreign pathogens
Contractile Actin, myosin Effect muscle contraction
Storage Legume storage proteins, egg white (albumin) Provide nourishment in early development of the embryo and the seedling

Proteins have different shapes and molecular weights; some proteins are globular in shape whereas others are fibrous in nature. For example, hemoglobin is a globular protein, but collagen, found in our skin, is a fibrous protein. Protein shape is critical to its function, and this shape is maintained by many different types of chemical bonds. Changes in temperature, pH, and exposure to chemicals may lead to permanent changes in the shape of the protein, leading to loss of function, known as denaturation    . All proteins are made up of different arrangements of the same 20 types of amino acids.

Questions & Answers

what is science?
Benedict Reply
Science is the method of acquiring skills and knowledge through experimentation and observation in the World Series
Richmond
where does meiosis occur in male plant reproductive organ
Gimai Reply
plant cell is plasmolysed as a result of the
Favour Reply
of the plant losing water
Esnart
"Head of a pin" means what?
Theresah Reply
types of genotype and types of blood group
Adebusuyi Reply
what is biology
Musa Reply
is the study of cell and structure of an organism
Atem
is the study of characteristics,life processes and phenomana of living organism
Atem
What is Monomer of protein?
Dimpho Reply
What's nutrition and types of nutrition
Jessica Reply
Why is cheetah d fastest animal
Jessica Reply
because they are capable of reaching speeds of up to 70mph
Abu
Thanks
Jessica
what is a cell
Reuben Reply
what is an enzymes
Reuben
a cell is a biological catalyst that speeds up the rate of a chemical reaction without itself been changed
Israel
a cell is smallest unit of life
Francis
an Enzyme helps speed up a chemical reaction
Francis
is the basic structural and functional unit of all organism
Atem
what is deamination
Mutebi Reply
Is the removal of amino radical from amino acid or any other amino compound.
Esnart
what is metabolism
Allen Reply
metabolism is the the combination of all the reaction that occur within your body
xjuicy_editzz
These reaction can be either anabolic (which is the building up of molecules) or can be catabolism (breaking of molecules) but these processes occur simultaneously to maintain homeostasis(internal body environment) within the body.
xjuicy_editzz
hope that helps :D !!
xjuicy_editzz
list 20 element in their order
Dor Reply
hydrogen helium lithium beryllium boron carbon nitrogen oxygen fluorine neon sodium Magnesium aluminium silicon phosphorus sulfur chlorine Aaron potassium calcium -Also if anyone is having trouble remembering the elements I recommend watching "The Periodic Table of elements song" :)
xjuicy_editzz
anabolic, Because ATP is needed
Avuyileji Reply
?
xjuicy_editzz
definition of biology
LENARD Reply
the branch of science that deals with the study of plants and animals
Emmanuel

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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