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Proteins - PowerPoint PPT Presentation

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Proteins. …..a recap. Characteristics of Proteins. Are made up of monomers These are called amino acids There are 20 amino acids And they all have the general molecular structure:.

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…..a recap

Characteristics of proteins
Characteristics of Proteins

  • Are made up of monomers

  • These are called amino acids

  • There are 20 amino acids

  • And they all have the general molecular structure:


Proteins are coded for by DNA (genes), transcribed (re-written) to mRNA and then translated into protein molecules at the ribosome.

You’ll learn a little more about this year when we study cell structure, a lot more next year when you study the molecular basis of genetics.

Polypeptide to functional protein
Polypeptide to Functional Protein

  • Refer to your handout “Atoms, Molecules and Biological Compounds”

  • The final shape or “conformation” of a protein is determined by the sequence of amino acids it contains.

  • How a protein functions is determined by its three dimensional characteristics.


Levels of Structure of a Protein

Roughly linear forming strands or sheets, fibrous proteins

One or more polypeptide chains take on a rounded, globular shape

Also check out pg 44-47, Bio-12

A couple of questions for you
A couple of questions for you…..

  • What is and what causes sickle cell anemia? ( pg 45, Bio-12)

  • What makes spider silk so strong?

  • What are some examples of proteins in a quaternary structure?

  • What is denaturation? What is the consequence of such an event?

  • Check out figure 34 c pg 47… learn how a “perm” works!!

  • Read “Directions in Science” from Handout.

Functions of proteins
Functions of proteins

  • Fibrous:

  • Play a structural role such as: collagen found in cartilage, bones, tendons, and blood vessels

  • Globular:

  • Regulatory: hormones ( growth, insulin, sex)

  • Transport: hemoglobin, in cell membranes

  • Protective: antibodies

  • Catalytic: Enzymes

A closer look at a special protein enzymes
A closer look at a special protein… Enzymes

  • Answer the following questions so that you understand your answers: Ref pg 69-72 (12)

  • What is an enzyme?

  • What is the substrate?

  • In simple, simple terms how does an enzyme work?

  • Why can’t living cells rely on high levels of heat to activate metabolic reactions?

  • What does the name “maltase” tell us?

  • What things affect enzyme activity?

  • Pre-read “Investigating the Effect of Temperature on Enzyme Activity” page 82 (12)


Overview: What would happen to your cells if they made a poisonous chemical? You might think that they would die. In fact, your cells are always making poisonous chemicals. They do not die because your cells use enzymes to break down these poisonous chemicals into harmless substances.

In this lab, you will study an enzyme that is found in the cells of many living tissues. The name of the enzyme is catalase (KAT-uh-LAYSS); it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances--water and oxygen. The reaction is as follows: 2H2O2 ----> 2H2O + O2 This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and die.


Many of these autoxidation reactions do not produce hydrogen peroxide directly, but rather superoxide (the product of adding one electron to an oxygen molecule). In order to get rid of superoxide (which is more toxic than hydrogen peroxide) the body also contains lots of superoxide dismutase, that converts the superoxide into water and hydrogen peroxide. One of the most interesting sources of superoxide in the body is that produced by white blood cells when they encounter harmful microorganisms. The white blood cells produce very large amounts of superoxide, hydrogen peroxide, and even hypochlorous acid (household bleach!) to kill the germs, just like in the TV ads.