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Some organisms have a CELL WALL

Learn about the vital functions of cell walls and membranes, their structures, and components in maintaining the integrity and functionality of cells. Explore the role of phospholipids, proteins, and cholesterol in the fluid mosaic model.

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Some organisms have a CELL WALL

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  1. Some organisms have a CELL WALL • Plants(cellulose) • Algae (polysaccharide) • Fungi(chitin) • Prokaryotes(peptidoglycan)

  2. What does the cell wall do? • Scaffolding - mechanical support and structure • Protection • Involved in Cell-cell communication • Maintenance of structure (turgor)

  3. ALL cells have a cell membrane!

  4. What do membranes do? • Protective barrier • Cell-Cell signalling • Transport of nutrients, products and waste products • Localisation of function within organelles Cell membrane function

  5. Membranes are ALSO locatedinside eukaryotic cells, separating individual organelles • Cell membrane (double membrane) • Organelles (membrane-bound) can be single or double membrane) • Secret Universe • Introduction to cell membrane

  6. What do membranes do? All cells live in an aqueous environment (surrounded by water, ions and molecules) • …they must control what gets in (nutrients) and out ( waste products and signalling molecules) • they need to communicate with each other… How is this achieved?....

  7. Where is the water in your body?

  8. Cell membranes separate your body into different compartments

  9. Membranes are: • Semi-permeable: controls entry and exit of substances • Self-sealing • Flexible, mobile fluid mosaics

  10. Let’s meet the components of the cell membrane

  11. You need to know and understand THIS model of the (cell) membrane

  12. Let’s start simply…… Membranes begin with a PHOSPHOLIPID BILAYER

  13. What’s a phospholipid? • Consist of a polar head (hydrophilic) composed of a glycerol and a phosphate molecule • Consist of two non-polar tails (hydrophobic) composed of fatty acid (hydrocarbon) chains • Since phospholipids contain both hydrophilic (water-loving) and lipophilic (fat-loving) regions, they are classed as amphipathic

  14. Substances can be hydrophilic or hydrophobic

  15. Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads

  16. The cell membrane is more than a phospholipid bilayer…. It’s officially described as a FLUID MOSAIC, studded with proteins, cholesterol and sugar molecules

  17. The fluid mosaic model

  18. Why fluid mosaic? • Cell membranes are represented according to a fluid-mosaic model, due to the fact that they are: • Fluid– the phospholipid bilayer is viscous and individual phospholipids can move position • Mosaic– the phospholipid bilayer is embedded with proteins, resulting in a mosaic of components

  19. Membranes are studded with the lipid cholesterol • In all animal cells • Influences membrane fluidity and permeability to some solutes – more cholesterol = less fluidity • Helps membranes curve into concave shape

  20. The phospholipid bilayer is studded with proteins

  21. We can classify proteins based on their LOCATION or their FUNCTION LOCATION • Integral– spans the whole membrane • Peripheral– only located in one or other layer of the phospholipid bilayer FUNCTION • Carrier proteins (PUMPS) – move substances through membrane using energy • Channel proteins - move substances through membrane with no need for energy • Glycoproteins– used for cell signalling • Receptor proteins – used to respond to information form the outside

  22. Protein channels move substances from one side of membrane to the other

  23. Protein carriers (pumps) use energy to move substances across the membrane

  24. Protein receptors

  25. Glycoproteins (sugars attached to the protein) are used for communication • ‘Chemical identification cards’ • Used for cell communication • Used by the immune system to identify self or ‘non-self’ (invaders)

  26. Blood cells have glycoproteins (blood type)

  27. Let’s Review… Let's build a membrane from scratch… And now…let’s make a membrane!

  28. Movement across the Cell Membrane

  29. 3.5.4 State that the energy for diffusion comes from the kinetic energy of random movement of molecules and ions • Particle theory states that all matter consists of many, very small particles, which are constantly moving, or in a continual state of motion. The degree to which the particles move is determined by the amount of energy they have and their relationship to other particles

  30. 3.4.2 Explain the importance of the membrane proteins to transport across the membrane

  31. 3.5.1: Diffusion: Definition • Diffusion is the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement • Works for small particles

  32. Simple Diffusion 2nd Law of Thermodynamics governs biological systems: the universe tends towards disorder (entropy) Diffusion: movement of small, soluble particles from highlow concentration

  33. Diffusion Movement is from HIGH to LOW concentration • “passive transport” • no energy needed movement of water diffusion osmosis

  34. 3.5.3 substances move into and out of cells by diffusion through the cell membrane; this is a dynamic process (always happening) • Gas exchange in the lungs • Gas exchange in plants

  35. Gas exchange between lungs and blood is via diffusion

  36. Gas exchange in plants is via diffusion

  37. Modelling diffusion using dialysis tubing

  38. 3.4.2 Explain the importance of the membrane proteins to transport across the membrane

  39. high low Facilitated Diffusion Facilitated diffusion is diffusion of specific molecules through protein channels in the cell membrane • no energy is required facilitated = with help open channel = fast transport

  40. Factors affecting diffusion • Concentration gradient • Temperature • Surface area for diffusion • Distance for diffusion • (size of particle) • (charged or uncharged)

  41. Factors affecting the rate of facilitated diffusion are the same as for simple diffusion • Concentration gradient • Temperature • Surface area for diffusion • Distance for diffusion

  42. How do things get into and out of our cells? PASSIVE MECHANISMS These don’t require energy • Simple diffusion • Facilitated diffusion • Osmosis ACTIVE MECHANISMS These require energy to transport substances (often against their concentration gradient) • Protein pumps • Endocytosis/ exocytosis

  43. Active transport 1: Protein pumps • Active transport uses energy (usually ATP) to transport substances into/out of the cell • The energy is used to change the shape of the ‘protein pump’ and thus import/export specific molecule • Active transport does NOT require a concentration gradient • Active transport frequently moves substances AGAINST a concentration gradient • Animation • protein pumps in plants

  44. Classic active transport protein pump: the sodium potassium pump

  45. Classic active transport pump 2: the proton pump on mitochondrial/ chloroplast membranes

  46. Plants depend on active transport for uptake of mineral ions (and water!)

  47. Active Transport 2: Endocytosis and Exocytosis • A simple one... • Animation • Animation 2 • Endocytosis/ exocytosis are import/export of materials by infolding/outfolding of the cell membrane • Cells use this for BULK transport

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