Cell Structure Notes PDF

**Ch 1 Cells** - What do living organisms need to exist? → An energy source - (for metabolic processes) → Liquid water - (Biochemical reactions occur in water. Water is also needed to dissolve chemicals and cellular transport) → The chemical building blocks required for life - (in...

**Ch 1 Cells** - What do living organisms need to exist? → An energy source - (for metabolic processes) → Liquid water - (Biochemical reactions occur in water. Water is also needed to dissolve chemicals and cellular transport) → The chemical building blocks required for life - (including carbon, oxygen, nitrogen, and hydrogen) → Stable environmental conditions - (like pressure, temperature, pH, light intensity, and salinity) - All living things share the following attributes: **M -** Movement: **R** - Respiration: converting glucose into ATP **S -** Sensitivity to stimuli: responding to environment **G -** Growth **R** - Reproduction: can be sexual or asexual **E** - Excretion **N** - Nutrition: intake of food or nutrients **D** - DNA - What is found in every cell? - Cytosol (cytoplasm) - Plasma membrane - Nucleus - Mitochondria - Ribosome - Golgi apparatus - Endoplasmic reticulum - Deoxyribonucleic acid - DNA - The cell theory - Cell theory was developed in 1839 - Developed by Theodor Schwann - Matthias Schleiden - The three tenets of cell theory - All organisms are composed of one or more cells - The cell is the basic unit of structure and organisation in organisms - All cells come from pre-existing cells - Video notes - Anton van levanhook invented his own microscope - discovered bacteria by looking at dental scraping - called bacteria animalcules - Robert Hook - invented the name The cell - never saw true cells only saw dead cells - named after prison cells - Developed by Theodor Schwann - Matthias Schleiden - Schleiden believed that all cells did not come from other cells - Robert Remack - proved that all cells come from pre-existing cells - Prokaryotes vs Eukaryotes Prokaryotes - First living organisms on earth - contain no distinct nucleus as they lack a nuclear membrane - lack membane bound organelles (have ribosomes) - examples: bacteria, cyanobacteria and archaea - DNA is found in the nuclioid - Prokaryotic cells are made up of: - **capsule** - made of polysaccharides - **cell wall** - made of peptidoglycan - **cell (plasma)** - controls what enters and leaves - **large, circular DNA** - **ribosomes** - synthesise proteins - **plasmids** - smaller pieces of DNA - **cytosol** - what everything floats in Eukaryotes - have a nuclear membrane (a distinct nucleus) and also have membrane bound organelles. - larger than prokaryotic cells - examples: animal, plant, protist, & fungal cells - DNA is found in the nucleus - **DORA** **D -** DNA **O** - Orgaanelles - The shapes of cells - cells come in a variety of shapes and their shapes are reflective of their functions - some cells can change shapes such as: - white blood cells - amoebas - cancer cells - Surface area to volume ratio - Unicellular organisms can survive successfully as an independent single cell. Why are there no large unicellular organisms? - The surface area to volume ratio (SA : V) is a measure of the balance between the surface area available for substance exchange and the volume of the cell. - The surface area of a cube is given by the equation: SA = 6L\^2 - Where L = the length of one side of the cube. - The volume of a cube is given by the equation V = L\^3 - As a cube increases in size, the volumes enlarges faster than their surface areas expand. The SA: V ratio of a smaller shape/ - As cells increase in size (larger cytoplasm), both their surface areas and volumes increase, but *not* at the same rate. The internal volume expands at a grater rate than the areas of their plasma membrane. Therefore, the growth of an individual cell is accompanied by a relative decrease in the area of it its plasma membrane. **Total Surface area** **6** **150** **750** ------------------------- ------- --------- --------- **Total Volume** 1 125 125 **Surface area/Volume** 6 1.2 6 - Video notes: - Single celled organisms - Continuously carry out chemical reactions - Absorb Resources - Oxygen - Glucose - Amino acids - Get rid of waste - Co\^2 - **Surface area : Volume** decreases as objects get larger - Bacteria - Have high SA:V ratio - can rely on diffusion - Humans - can't rely on diffusion - specialised exchange surfaces - increase SA:V ratio - As organisms get larger - The distance that molecules would have to diffuse to get from the oustide of their body to the inside of their body increases massively - To solve this larger organisms often have transport systems - Circulatory system - As the volume of a cell increases, the metabolic needs of the cell increases (this requires an increase in the inputs and outputs of materials across the plasma membrane). - This increase in materials can only increase in proportion to the cell's SA. - As a cell increases in volume, its metabolic needs increase faster than the cell's ability to transport the materials into and out of the cell. This explains why metabolically active cells are so small. - The rate at which nutrients enter and wastes leave a cell is generally inversely proportional to the cells size. (measured in metabolically active cytoplasm). This means that the larger the cell, the slower the rate of movement of nutrients into and wastes out of a cell. - The cells that function in the absorption of digested nutrients (small intestine) compensate for this decrease with increasing size in the same way as the hand to the right. - They greatly increase their surface area with only a minimal increase in cell volume by extensive folding of the plasma membrane on the cell surface that faces into the gut lumen - called microvilli - A single cell lining the small intestine may have up to 10 000 microvilli on its apical surface facing into the gut lumen. **The cell is creating as much surface area as possible whilst keeping the ratio low.** - Organelles **Endosymbiont:** cell living inside another cell **Obligate** **endosymbiont**: a organelle that cannot live without the cell - All plant and animal cells contain the following: - nucleus/nuclear membrane - nucleoles - plasma membrane - ribosomes and peroxisomes - cytoskeleton - cytosol - endoplasmic rectiulum - mitochondria - golgi apparatus - Ribosomes - found in all cells (even prokaryotic cells) - no membrane - extremely small - made of ribosomal RNA (rRNA) & proteins - read messenger RNA (mRNA) from the nucleus - converts into amino acid & protein - free floating or attached to the ER - Proteins - haemoglobin - contractile proteins: actin, and myosin - insulin & lipase - antibodies found in white blood cells - Nucleus - houses DNA - spherical structure enclosed within a double walled membrane - controls DNA replication during call division - initiates gene expression - control of metabolic activities - Nucleolus - composed of RNA - produces (rRNA) - not enclosed within a membrane - Mitochondria - energy production - produces ATP in the process of cellular respiration - can be seen with electron microscope only - double membrane organelle - the more active the cell the more mitochondria - red blood cells have none (mature) - C 6 H 12 O 6 + 6 O 2 \--\> 6 CO 2 + 6 H 2 O + ATP - Endoplasmic Reticulum - rough ER has ribosomes attached to their membrane - processing and transmitting proteins - adding sugar groups - folding proteins into functional shapes - smooth ER - synthesis lipids (including testosterone) - detoxifies harmful hydrophobic products of metabolism & barbatute drugs - breaks down glycogen into glucose for export - Golgi apparatus - layered structure - proteins from rough ER transferred through golgi apparatus - proteins are packaged into secretary vesicles - from golgi apperatys they open and merge with the plasma membrane - Lysosomes - spherical shape containing about 50 digestive enzymes - functions - digestion of excess macromolecules within a cell - autophagy - the breakdown of non-functioning cell organelles - Peroxisomes - cellular metabolism - oxidisation of fatty acids - break down of substances that are toxic - contains a large number of enzymes - breaks down hydrogen peroxide - **2H2O2 (l) → 2H2O (l) + O2 (g)** - catalyse - Cytoskeleton - 3D frame work of eukaryotic cells - Functions - supplying support and strength for the cell - cell shape - cell mobility - movement of cell organelles - moving chromosomes during cell divisions 3 components - Microtubules - hollow tubes which move material within cells a gives cillia and flagella structure & motion - Intermediate filaments - Microfilaments - responsible for for most cell move ment consists of actin - Cilia and Flagella - some unicellular eukaryotes depend on cilia and flagella to move - flagella generally singular - like a tail - cillia are shorter and more numerous - Cell membrane - active and selective barrier - where messages from outside the cell are received - if a cell doesn't display the correct molecules an immune response takes place and the cell dies - transports materials between the intracellular and extra cellular environment - Crossing the Plasma Membrane - what type of molecule it is: - hydrophilic - hydrophobic - the size of the molecule - whether there is a difference in concentration gradient - Passive transport - does not require energy to occur as the molecules move - molecules move along a concentration gradient - high concentration to low concentration - Active transport - movement of molecules or ions across a cell membrane - requires ATP - moves against the concentration gradient - low concentration to high concentration - Bulk transport - large molecules (proteins) need vesicles through the membrane - Simple diffusion and Facilitated diffusion - *The passive movement of solutes through the phospholipid bilayer, from a high to a low concentration, following the concentration gradient* - Factors affecting rate of diffusion - **concentration**---the greater the concentration gradient, the faster the rate of diffusion. - **temperature**---the higher the  temperature, the higher the rate of diffusion, due to faster   molecular movement. \*\*\*\* - **particle size** ---smaller particles increases the rate of diffusion through a membrane. - Facilitated - occurs when molecules are moved in special protein transporters - passive process - transporters are either channel proteins of carrier proteins - **channel proteins** - do not change shape - diffuses charged particles and polar molecules - **carrier proteins** - do change shape - transport hydrophylic uncharged substances - The plasma membrane has 2 main components: - **Phospholipid bilayer:** - Two layers - Hydrophobic tails face each other - Consists of two fatty acid chains joined to a phosphate containing group - The phosphate containing head is hydrophilic - The fatty acid chains are hydrophobic - The head faces the cytosol - at body temp the chains are viscous fluids - fluid - flexible - soft - able to move freely - Enabling red blood cells to squeeze through capillaries - Because they can change shape - **Proteins**: - Proteins can be embedded in the bilayer - They can move freely within the bilayer - Integral proteins - Embedded in the phospholipid bilayer - Spans the width of the plasma membrane - Transmembrane proteins - If carbohydrate groups like sugars are attached to the exposed part of these protein - Glycoproteins - Peripheral proteins - Can be anchored to the exterior of the plasma membrane by bonding to lipids - Indirectly associated with the plasma membrane through interactions with integral proteins in the membrane **6 Roles of Proteins in the Cell Membrane** - **T**ransport - Trans-membrane proteins allow movement of the hydrophilic substances across the phospholipid bilayer - They can travel through: - Channel proteins - Open to all molecules to diffuse in to and out of the cell - These substance are usually small and charged like ions - Carrier proteins - allow the movement for larger molecules - **R**eception - receptors for signalling molecules - peptide or amino acid-based molecules - When the signal inds to the receptor protein it alters the shape of - **A**nchorage - Proteins connect the intracellular cytoskeleton to the extracellular matrix - Proteins on the cell surface are linked to collagen fibres and peptidoglycan filaments that have been excreted by cells - **C**ell identity - Proteins mark the cell as belonging to 'self' - Can be: - Glycoproteins - Antigens - Cell identity tags - In mammals these markers let the immune system to identify the cells as "self" - Glycolipids on the plasma membranes play a role in tissue recognition - **I**ntercellular joinings - Proteins involved with plasmodesmata and tight junctions - They join cells together and facilitate communication between cells - This lets efficient functioning of tissues occur - **E**nzymatic activity - Enzymes are proteins that **catalyse** reactions by lowering activation energy - They bind the substrates and weaken the bonds to initiate the reaction - Enzymes are **specific** - they only bind to one or two substrates - they are not altered during the process - They facilitate a other biochemical pathways - Such as the production of ATP **Other components** - **Cholesterol** - maintains membrane stability and fluidity - it reduces membrane fluidity - **Carbohydrates** - Occurs over external surface of the membrane allows for identification at the cytoplasm - attach to proteins or lipids - glycoproteins - cell identity - intercellular joinings - glycolipids - cell identity