Term 1Revision Biology 12

Cell membranes Sketch a typical cell membrane according to the Fluid Mosaic model Describe the roles of: Phospholipids Proteins Carbohydrates

Cells Sketch a typical cell membrane according to the Fluid Mosaic model. Describe the roles of: Phospholipids = A – waterproof, flexible layer, that lets in small particles Proteins = B – provides channels for larger particles (facilitated diffusions), acts as pumps (active transport), acts as receptor sites Carbohydrates = C - acts as receptor sites A B C

Exchange of material Show the movements of water and ions that would occur in both these cases Distilled water Sea water

Exchange of material Show the movements of water and ions that would occur in both these cases Distilled water Sea water Water moves in Water moves outIons move in Ions move out

TEE Extended answer a Genetic information is stored in molecules of DNA. Using labelled diagrams describe the structure of DNA at the level of major components and describe how it carries genetic information

Extended answer a) Genetic information is stored in molecules of DNA. Using labelled diagrams describe the structure of DNA at the level of major components and describe how it carries genetic information One mark/dot point in answers below unless otherwise indicated. Maximum 10 marks/question. Diagram – showing nitrogenous base pairs - A T, C G, and sugar phosphate backbone one mark for nitrogenous pairs label on the figure, 2 marks for sugar phosphate backbone label (3 marks total) nucleotides double helix one mark for correct basic structure in the figure name bases (one mark for naming all 4) indicate pairing (each correct pairing = one mark) sequence of bases codes for amino acid structure triplet code/codons relationship to amino acids The information is carried within the DNA by the sequence of base pairs. Each segment of 3 nucleotides codes for one amino acid & is called a codon This information is copied to mRNA in the nucleus and carried to the ribosomes, determining which proteins are made

Structure of DNA

nucleotides Adenine Guanine sugar phosphate

Protein synthesis Transcription Translation Codon Anticodon t-RNA m-RNA r-RNA Protein Amino acid

Protein synthesis Transcription – copying of RNA from DNA Translation – reading of mRNA at ribosome Codon – 3 nucleotide section on mRNA that codes for an amino acid Anticodon - 3 nucleotide section on tRNA that matches codon, tRNA brings the right amino acid t-RNA – carries amino acid m-RNA – codes for sequence of amino acids r-RNA – makes up ribosomes Protein – long chain of amino acids (end product) Amino acid – unit that is put together to make protein

DNA replication Occurs in One set of enzymes Another set of enzymes Nucleotides match up by the (C, A ) The end result is joined at a point called the

DNA replication Occurs in nucleus One set of enzymes splits DNA Another set of enzymes adds new nucleotides Nucleotides match up by the base pairing rule (C - G, A - T ) The end result is 2 strands (chromatids) joined at a point called the centromere

Stages of mitosis

Interphase – normal cell metabolism & growth, DNA replication Prophase – nucleus disappears, spindle forms, chromosomes condense & become visible Metaphase – chromosomes line up on equator Anaphase – chromatids split & move to opposite ends of cell Telophase – new nuclei form, cytoplasm divides to form 2 new cells Interphase - normal cell metabolism & growth

Identify the stages of mitosis

telophase anaphase metaphase interphase prophase

TEE - Extended answer d Most genes in the body carry information about the structure of enzymes, highlighting the importance of enzymes to cellular function. Describe the functions of enzymes in cells and explain why enzymes are so specific in their action. Discuss the factors that affect enzyme activity, and describe their effects

Extended answer d) Most genes in the body carry information about the structure of enzymes, highlighting the importance of enzymes to cellular function. Describe the functions of enzymes in cells and explain why enzymes are so specific in their action. Functions of Enzymes (max 7 marks): catalysis speed up reactions reduce activation energy synthesis / anabolism & example digestion / catabolism & example energy production & example control of chemical pathways / energy production Enzyme Specificity: Caused by active site / 3D shape Formation of enzyme – substrate complex / lock & key model Good diagram of lock & key model Enzymes work within narrow pH ranges Enzymes work within narrow temperature ranges Discuss the factors that affect enzyme activity, and describe their effects Increasing temperature increases activity, unless it gets too hot and the enzyme is destroyed Changing pH alters shape of enzyme  reduces activity Increasing substrate concentration increases activity (up to maximum) Increasing enzyme concentration increases activity (up to maximum) Decreasing product concentration decreases activity Increasing cofactor concentration increases activity (up to maximum) Presence of inhibitors decreases activity