Chapter 3 – pp Unit III: Lively Molecules Cellular Control

Nucleus nucleoli chromatin Nucleic Acids: Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) Cellular Control

Polymer of nucleotides Consists of: –sugar deoxyribose (DNA) –phosphate group –nitrogenous base Adenine (A) Thymine (T) – DNA only Cytosine (C) Guanine (G) Nucleic Acid Structure

DNA Structure Two chains of nucleotides DNA base pairings: –A-T –C-G –T-A –G-C Law of complementary base pairing –one strand determines base sequence of other Segment of DNA

DNA Structure DNA molecule described as double helix.

Code for protein synthesis Gene – information-containing segment of DNA that codes for the production of a molecule of RNA Genome - –humans have estimated 25-35,000 genes –98% of DNA noncoding – “junk” or regulatory DNA Function

RNA smaller than DNA –transfer RNA –ribosomal RNA –messenger RNA Only one nucleotide chain –ribose –uracil Essential function –interpret DNA code –direct protein synthesis in the cytoplasm RNA Structure and Function

Law of complimentary base pairing Steps of replication process 1.DNA unwinds from the histone proteins in the chromosome 2.DNA helicase opens short segment of helix replication fork is point of separation 3.DNA polymerase assembles new strand of DNA next to one of the old strands Semiconservative Replication >2 DNA polymerase enzymes at work simultaneously DNA Replication

4 nucleotides (A,T,G,C) code for the 20 amino acids Base triplet: –a sequence of three nucleotides (ex. TAC) –instructions for 1 amino acid Codon: –“mirror-image” sequence in mRNA (ex AUG) –64 possible codons (4 3 ) often 2-3 codons represent the same amino acid start codon = AUG 3 stop codons = UAG, UGA, UAA The Genetic Code

Copying instructions from DNA to RNA 1.DNA uncoils and “unzips” –transcribes to make pre-mRNA –Pre-mRNA contains: Introns - “nonsense” Exons - “sense” 2.Enzymes remove introns and splice together exons = mRNA Protein Synthesis: Transcription

One gene can code for more than one protein Exons can be spliced together into a variety of different mRNAs. Alternative Splicing of mRNA

Protein Synthesis: Translation

Summary of Transcription and Translation

Protein molecules must coil or fold into proper 2 nd and tertiary molecular structure Chaperone proteins –prevent premature folding –assist in proper folding Stress or heat-shock proteins –help damaged protein fold back into correct functional shapes Protein Structure

Proteins destined for secretion or packaging are assembled on rough ER and sent to Golgi complex Removal of amino acids, folding, forming disulfide bridges or addition of carbohydrates Protein Synthesis: Post-Translational Modification

Nucleus Rough ER Golgi complex Lysosome Ribosomes Protein packaged into transport vesicle, which buds from ER. Transport vesicles fuse into clusters that unload protein into Golgi complex. Golgi complex modifies protein structure. Golgi vesicle containing finished protein is formed. Secretory vesicles release protein by exocytosis Clathrin-coated transport vesicle Protein formed by ribosomes on rough ER. Protein Synthesis: Post-Translational Modification

Chapters: 2 – Organic molecules & Enzymes 3 – Transport of molecules, Cellular control 22 – Cellular respiration Lab Practical: Questions from lab manual Experiments Exam 3