OCR Unit 3/4 Biology Head Start PDF

Unit 3 / 4 Biology - HeadStart Key points Five areas of study (4 content; 1 scientific skills) New study design started in 2022 Several areas won’t be covered in past textbooks and exams Detailed study design in Google Classroom – this is your Biology Bible of all essential con...

Unit 3 / 4 Biology - HeadStart Key points Five areas of study (4 content; 1 scientific skills) New study design started in 2022 Several areas won’t be covered in past textbooks and exams Detailed study design in Google Classroom – this is your Biology Bible of all essential content for the year Jacaranda Textbook is required for next year – Chapter One has been uploaded to Google Classroom for you to use during HeadStart What you’ll learn… Unit 3: Area of Study One Unit 3: Area of Study Two Nucleic acids (DNA / RNA) Biochemical pathways Proteins Photosynthesis Enzymes Cellular respiration DNA manipulation / CRISPR Biotechnology Unit 4: Area of Study One Unit 4: Area of Study Two Disease-causing pathogens Genetic change over time Responding to antigens Evolution of species Types of immunity Determining relatedness Disease challenges and strategies Human change over time Unit 3 Area of Study One The relationship between nucleic acids and proteins nucleic acids as information molecules that encode instructions for the synthesis of proteins; the structure of DNA; the three main forms of RNA (mRNA, rRNA and tRNA); and a comparison of their respective nucleotides. What are biomacromolecules? Large molecules that are essential for all living things Include nucleic acids, proteins, lipids, carbohydrates Are examples of polymers (any material made of long repeating chains of monomers) Tip: words in The process of monomers joining to make polymers is green are called polymerisation structures, and words in red are processes. Nucleic acids Information-carrying molecules DNA = RNA = Made of nucleotide monomers DNA nucleotide RNA nucleotide DNA Double-stranded molecule Nitrogen bases bond with hydrogen bonds Base-pairing rule: G-C: 3 hydrogen bonds A-T: 2 hydrogen bonds Phosphodiester bonds join sugar A condensation of one nucleotide and phosphate polymerisation occurs group of the next when two nucleotides Two strands run in anti-parallel join and a H2O molecule 3’ → 5’ 5’ ← 3’ is released. Winds in to double helix shape DNA Wraps around histones (proteins) Bundled in chromosomes Located in nucleus of eukaryote cells and loose in prokaryotes DNA does not leave the nucleus RNA Contains ribose sugars Single-stranded molecule No hydrogen bonds Has phosphodiester bonds Uracil replaces thymine Created in nucleus (mRNA / tRNA) or nucleolus (rRNA) from DNA template RNA leaves the nucleus and travels to cytoplasm RNA Three types of RNA: Type of Full name Function RNA A structural component of rRNA Ribosomal RNA the ribosome. Carries genetic information mRNA Messenger RNA from nucleus to ribosomes to direct protein synthesis. Transfers amino acids to tRNA Transfer RNA ribosomes for protein synthesis. Comparison of DNA and RNA Nucleic acids DNA both RNA Long linear molecule Nucleotide monomers Short linear molecule Deoxyribose sugar Pentose sugar Ribose sugar Thymine Adenine Uracil Double stranded Guanine Single strand Hydrogen bonds Cytosine Found in cytoplasm Found in nucleus Phosphodiester bonds Do now Outline three similarities and three differences between DNA and RNA. Unit 3 Area of Study One The relationship between nucleic acids and proteins the genetic code as a universal triplet code that is degenerate the steps in gene expression, including: Transcription; RNA processing; and translation by ribosomes. Gene expression (transcription, RNA processing, translation) Process of synthesising proteins from DNA code DNA → pre-mRNA → mRNA → polypeptide (folds in to protein) Polypeptides are made of monomers called amino acids The genetic code DNA provides the genetic code for the sequence of amino acids in a protein DNA bases are read in groups of three known as a “triplet” One triplet codes for one amino acid The genetic code is considered: Universal: the same specific triplet sequences code for the same amino acids in all organisms Degenerate / redundant: multiple triplets can code for the same amino acid (more on this later) Transcription *Worksheet error*: change “translation” to “transcription” DNA → pre-mRNA (Occurs in nucleus) 1. DNA is unwound and unzipped exposing coding strand and a template strand 2. RNA polymerase (enzyme) binds to the promoter region on template strand of DNA 3. RNA polymerase moves along DNA from 3’ to 5’ direction and joins complementary nucleotides to create a growing pre-mRNA strand Uracil replaces Thymine (U pairs with A) Each 3 bases of mRNA is known as a codon  DNA contains coding RNA processing regions called exons and pre-mRNA → mRNA (Occurs in nucleus) non-coding regions called introns. 1. A methyl cap is added to the 5’ end of pre-mRNA 2. A poly-A tail is added to the 3’ end 3. The introns are spliced out and exons joined together mRNA triplets are known as codons. Mature mRNA leaves nucleus and travels to ribosome. Translation mRNA → protein (Occurs at ribosome) 1. 5’ end of mRNA threads through ribosome 2. tRNA molecules have anticodons (triplets) and carry specific amino acids 3. Anticodon of tRNA binds with complementary codon on mRNA 4. Adjacent amino acids are joined with peptide bonds Reading a codon table (codon → amino acid) All poplypeptides All poplypeptides start with the amino end with the codon acid “Met” coded UAA, UAG, or UGA for by the codon AUG Gene expression overview Unit 3 Area of Study One The relationship between nucleic acids and proteins amino acids as the monomers of a polypeptide chain the resultant hierarchical levels of structure that give rise to a functional protein. Protein structure Proteins are made of monomers called amino acids. Central Carbon and a Hydrogen Variable region (changes for each amino acid) There are 20 known types of amino acids. 11 are produced in humans… where do we get the rest? Polymerisation Amino acids are assembled in a specific order based on mRNA code (during translation) Carboxyl group of one amino acid joins to amine group of next → condensation polymerisation peptide bond is formed polymer is called a polypeptide chain (made of amino acid monomers) Further modifications must occur to polypeptide for it to become functional. Protein modification Specific protein shape is critical to its functioning Proteins must go through three (sometimes four) specific stages of structural modification to become functional  Hierarchical levels of protein structure Primary structure Secondary structure Tertiary structure Quarternary structure Amino acids in a Folds into repeating 3D shape formed Two or more specific sequence patterns called through R-chain polypeptide chains joined by peptide alpha-helices and interactions. Protein joined together. Only bonds. beta-pleated sheets. is fully functional. some proteins. Changes to protein shape Factors that can cause protein molecules to change shape include: High temperature Strong salty solutions pH changes If these factors are strong enough: H-bonds of the protein will break and it will lose it’s shape (denaturing / denaturation) The protein will no longer be functional