CHAPTER 4- DNA, PROTEINS

AND PROTEOMES

Year 12 Biology

2012

Ms Hodgins

LESSON 1- WHY IS DNA SO IMPORTANT?

We’ve all heard that DNA is important because it holds the instructions for life, but what does it actually do?

DNA holds all of the information needed to make PROTEINS. The information helps to ‘pull’ amino acids together to make polypeptides.

So why are PROTEINS so important? PROTEINS

Play fundamental roles in cell functioning Are enzymes Provide structure Provide support Transport materials into and out of cells Assist in cell recognition and signalling Act as hormones Support in bones and muscles Transport molecules around the body Provide defence mechanisms

PROTEINS ARE REALLY IMPORTANT FOR LIFE

WHAT IS DNA? Deoxyribonucleic Acid Found in the NUCLEUS of eukaryote cells Made up of chemical building blocks called

NUCLEOTIDES Each NUCLEOTIDE has

A phosphate group A 5-Carbon sugar (deoxyribose) (where the carbons

are numbered 1’ – 5’) A nitrogen containing base Adenine A, guanine G, thymine T, cytosine C)

DNA double stranded helix due to COMPLIMENTARY BASE PAIRING : A-T, G-C

ACTIVITY 1: Making nucleotides (Cut and Paste)

WHAT IS RNA? A copy of DNA Made in the nucleus, passes into

cytoplasm Differences-DNA RNA

Deoxyribonucleic Acid Ribonucleic Acid

Sugar is Deoxyribose Sugar is Ribose

Bases are A, T, G C Bases are A, G, C, U

Double Stranded Single Stranded

Nucleus Cytoplasm

WHAT IS THE END PRODUCT? We now know-

What DNA is.What RNA isWhy DNA is importantWhy PROTEINS are important

Let’s look at the final products. PROTEINS- How are they made- made

simple ACTIVITY 2: Making proteins made simple

PROTEIN FORMATION Amino acids have the same basic structure-

An amino group (NH4) A carboxyl group (COOH) A side chain (makes the amino acids different)

Refer to Fig 4.10 page 80 Amino acids link together with peptide bonds

(removing a molecule of H2O) Dipeptide = 2 amino acids joined together Tripeptide = 3 amino acids joined together Polypeptide = many amino acids joined

together in a chain PROTEINS are polypeptides

PROTEIN STRUCTURE

PRIMARY STRUCTURE- linear sequence of the amino acids

SECONDARY STRUCTURE- pleating or coiling of the amino acid chains caused by Hydrogen bonds forming

TERTIARY STRUCTURE- folding to create 3D shape determined by the number and sequence of amino acids. (Critical for its function e.g. enzymes)

QUATERNARY STRUCTURE- four polypeptide chains combining

ACTIVITY 3:Draw an interpretation of each structure

LESSON 1 QUIZ 1. What does DNA stand for? 2. What does RNA stand for? 3. What are the 3 substances required to make

a nucleotide? 4. What is the name of the sugar in DNA? 5. What is the name of the sugar in RNA? 6. Name the bases in DNA 7. Name the bases in RNA 8. How many strands does DNA have? 9. How many strands does RNA have? 10. In DNA, state which bases pair up to form

complementary base pairing.

LESSON 2- HOW DNA MAKES PROTEINS

ACTIVITY 1: Making Proteins Role-play The “raw materials” (amino acids) are

converted into a “product” (polypeptides)

11 out of the 20 amino acids are able to be made in human cells. The other 9 are essential amino acids and needs to be consumed as a part of the diet.

Amino acids are found in the cytosol of the cell.

HOW ARE THE CORRECT AMINO ACIDS SELECTED?

TRANSCRIPTION AND TRANSLATIONOrganelle / Substance Analogy

DNA of gene in the nucleus Masterplan with the complete set of instructions

mRNA Working copy of one instruction

Ribosomes Construction site

tRNA Carriers of raw materials

Amino acids Raw products

Protein chain (polypeptide) End product

TRANSCRIPTION- copying of a nucleotide sequence of DNA into the nucleotide sequence of RNA

TRANSLATION- assembly of a polypeptide according to the nucleotide sequence if RNA using the genetic code.

The genetic code – refer to page 76 Table 4.1ACTIVITY 2: Transcription and Translation Role-play

TRANSCRIPTION AND TRANSLATION ROLE PLAY Numbered 1 or 2- all 1’s together, all 2’s together Read pages 73, 74, 75 Create a short role play to show how genetic

information in the nucleus undergoes transcription and translation to create polypeptides

Include an explanation of Transcription Translation mRNA tRNA Locations where events occur Proteases Codons

Everyone in the group MUST have a role HAVE FUN!