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Unit 3 VCE Biology Cell membranes and organelles

Unit 4 VCE Biology: Cell membranes &_organelles

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Unit 4: Area of study 1: Biological macromolecules, cell membranes and organelles.

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Page 1: Unit 4 VCE Biology: Cell membranes &_organelles

Unit 3 VCE Biology

Cell membranes and organelles

Page 2: Unit 4 VCE Biology: Cell membranes &_organelles

Prokaryotic cell

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Eukaryotic (animal) cell

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Cell membrane – phospholipid bilayer

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Cell membrane with embedded proteins

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Two types of proteins in membranes:

• Integral proteins that are embedded or inserted into the cell membrane.

• Peripheral proteins that are attached to the surface of the cell membrane.

• The functions of these proteins include transportation, enzymes, receptor sites, cell adhesion and attachment to the cytoskeleton.

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Through the cell membrane

• Diffusion (passive)• Osmosis (passive)• Facilitated diffusion (passive)• Active transport (requires energy)• Bulk transport (requires energy)

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Diffusion

• Passive movement of molecules from an area of high concentration to low concentration.

• Concentration gradient is the difference in concentration between the two regions.

• Small, uncharged molecules (CO2, H20 and O2) move easily through the membrane.

• Works well over short distances, but slows once molecules enter the cell.

• Limits cell size.

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Diffusion (passive)

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Osmosis

• Osmosis is the process by which water moves through a semi-permeable membrane from an area of high concentration (of water) to lower concentrations.

• It is a passive process and therefor does not require energy.

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Osmosis – diffusion of water

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Facilitated diffusion

• Channel mediated - Some substances diffuse with the assistance of protein channels

• Carrier mediated - Substances move down the concentration gradient via specific carrier molecules. Slower than channel-mediated as the protein carrier has to change shape for each molecule it transports.

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Facilitated diffusion - passive

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Active Transport

• Movement of dissolved substances into or out of cells against a concentration gradient.

• Active transport requires energy and involves a carrier protein for each substance that is actively transported.

• Includes endocytosis (into cell) and exocytosis (out of cell).

• Transport vesicles fuse with the membrane to consume or excrete substances.

Page 16: Unit 4 VCE Biology: Cell membranes &_organelles

Active Transport

• Pinocytosis is when a liquid is consumed or excreted.

• Phagocytosis is when a solid substance is consumed or excreted.

• Cell walls lie outside the plasma membrane in plant, fungal and prokaryotic cells.

• Endocytosis and exocytosis can occur into and out of the cell vacuole.

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Active Transport – requires energy

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Bulk Transport – requires energy

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The Nucleus

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Mitochondrion

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Ribosomes• Ribosomes are cell

organelles consisting of RNA and proteins, found in the cytoplasm and sometimes along the endoplasmic reticulum (RER).

• Ribosomes are responsible for assembling the proteins in a cell.

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Nucleus with Rough Endoplasmic Reticulum (RER)

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Lysosomes

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Lysosomes

• Lysosomes serve as the cells digestive system.• They are membrane-bound organelles

containing enzymes that can break down individual proteins or complete micro-organisms.

• They are released from the golgi apparatus.

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Chloroplasts in plant cells

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Cytoskeleton

• The centrosome (in animal cells) creates microtubules that provide a spindle for mitosis and meiosis.