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Chapter 18: Problem 36

What are some of the functions of proteins in living organisms?

Short Answer

Expert verified
Proteins are essential components of living organisms and perform various functions, including acting as enzymes, providing structural support, transporting molecules, participating in cell signaling and communication, contributing to the immune system, and enabling muscle movement. Examples of proteins carrying out these functions are amylase, collagen, hemoglobin, hormone receptors, antibodies, and actin-myosin complexes.

Step by step solution

01

Introduction

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. They are essential components of living organisms, and they perform a multitude of functions within those organisms. The following steps will explain some of the primary functions of proteins in living organisms.
02

1. Enzymes

Proteins can function as enzymes, which are biological catalysts that speed up chemical reactions without being consumed in the process. Enzymes are crucial for processes like digestion, where they help break down food molecules into smaller units that can be easily absorbed and used by the organism. Examples of enzymatic proteins include amylase, which breaks down starches into sugars, and lactase, which breaks down lactose in milk.
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2. Structural Support

Some proteins provide structural support for cells and tissues. For example, collagen is a protein that forms the primary structural component of connective tissues such as tendons, ligaments, and skin. Other proteins, such as keratin, are responsible for the structure and durability of hair, nails, and the outer layer of the skin.
04

3. Transport

Proteins can serve as transport molecules, helping move substances across cell membranes or through the bloodstream. For example, hemoglobin is a protein found in red blood cells that transports oxygen from the lungs to other tissues throughout the body. Another example is the sodium-potassium pump, a protein that helps maintain cell membrane potential by actively transporting ions across the membrane.
05

4. Signaling and Communication

Proteins play a vital role in cell signaling and communication, enabling the transmission of information both within and between cells. This includes proteins like receptors, which receive signals from other proteins or molecules, and proteins that relay these signals within the cell or to other cells. Hormones, which are proteins or peptides, are essential for the regulation of diverse physiological processes, from growth and development to maintaining homeostasis.
06

5. Immune System

Proteins play a crucial role in the immune system, helping the body recognize and defend against foreign substances (e.g., bacteria, viruses) or damaged cells. Antibodies, also known as immunoglobulins, are proteins produced by the immune system to specifically identify and neutralize foreign objects like bacteria and viruses. Additionally, proteins such as interferons help cells communicate during an immune response.
07

6. Movement

Muscle contraction and movement are possible thanks to the presence of proteins. Actin and myosin are two proteins that interact with each other to cause muscles to contract. In a simplified explanation, myosin "pulls" on actin filaments, causing the muscle fibers to shorten and produce movement. This process happens in both skeletal muscles, responsible for voluntary movement, and smooth muscles, such as those in blood vessels and the digestive system.

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Most popular questions from this chapter

Below are shown the hydrogen bonds that form between the \(C-G\) and \(A-T\) pairs of bases. What type of functional groups are involved in hydrogen bonding? Why does the A-T pair form only two hydrogen bonds and not three?

(a) Draw the monomer 1-butene. (b) Draw the polymer formed from this monomer, making it at least three monomer units long. (Hint: There are no double bonds in the polymer.)

Carbomer, a polymer used to thicken cosmetic lotions and creams, is a polymer of the monomer known as acrylic acid, shown below. Polymerization occurs due to the \(\mathrm{C}=\mathrm{C}\) double bond as it does for polyethylene. (a) Draw the polymer. (b) When this polymer is exposed to aqueous base, it deprotonates, and the resulting carboxylate anion hydrogen bonds to water very well, causing thickening of the aqueous solution. Draw this polymer in its deprotonated form, and show how water would hydrogen bond to it.

This polymer is called silicone and has a noncarbon, "inorganic" backbone of alternating silicon and oxygen atoms: (a) Put a set of parentheses around one monomer unit. (b) Another name for this polymer is polydimethylsiloxane. Explain why it has this name.

Protein molecules are usually quite large and yet often water-soluble. They are soluble in water because they can fold themselves into spherical shapes in which the polar (hydrophilic) side chains are on the surface and the nonpolar (hydrophobic) side chains are buried inside the sphere. Of the amino acids Ala, Ser, Phe, lle, Arg, and Asp, (a) Which would you expect to find on the surface of a water-soluble protein? (b) Which would you expect to find buried deep inside the protein structure? (c) Which might be in either location depending on the solution pH?
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