Cell Biology - Topic 1
- Created by: Riya.b123
- Created on: 10-02-19 13:11
Prokaryotes & Eukaryotes
- Prokaryotic cells are smaller & simpler.
- e.g. Bacteria
- single-celled organism
- Eukaryotic cells are complex
- include animal & plant cells
Animal Cells & Plant Cells
- Nucleus - controls activity of cells ( genetic material)
- Mitochondria - where aerobic respiration takes place
- Cytoplasm - where chemical reactions take place
- Cell Membrane - holds cell together
- Ribosomes - where proteins are made
- Plants also contain :
- Cell Wall - made of cellulose - supports & strengthens cell
- Chloroplasts - where photosynthesis takes place (chlorophyll)
- Permanent Vacuole - contains cell sap
Bacteria Cell
- Are prokaryotes
- No nucleus, chloroplasts or mitochondria
- Circular strand of DNA - floats freely in cytoplasm
- Small rings of DNA called plasmids
Light Microscope & Electron Microscope
- Light miscroscopes use light & lenses to form image of specimen.
- see individual structures & large subcellular structures
- Electron microscopes use electrons to form an image
- Higher magnification & higher resolution than light microscopes
- See small things in detail (internal structures)
Microscopy - Required Practical
- Prepare slide
- Add drop of water to clean slide
- Using tweezers peel of epidermal tissue from onion & place on slide
- Add drop of iodine to stain
- Place coverslip & clip to stage on microscope
- Select lowest powered objective lens & look using the eyepiece with coarse adjustment knob to focus
- Adjust fine adjustment knob until clear image seen
Cell Differentiation
- Cells develop different subcelleluar structures & turn into different types of cells
- Most animals ability to differentiate lost at early stage
- Plants don't lose ability
- In mature animals used for repairing & replacing cells
- Undifferentiated cells called stem cells
Examples of Specialised Cells
Sperm Cells - specialised for reprodcution (Male DNA to Female DNA) - long tail & streamlined head to swim - Mitochondria - Enzymes.
Nerve Cells - carry electrical signals to parts of the body - long - branched connections
Muscle Cells - contract quickly - long - lots of mitochondria - energy
Root Hair Cells - absorbing water & minerals - on surface if plant roots - big surface area
Phloem & Xylem - transporting substances (food & water)
Stem Cells
- Divide to produce more undifferentiated cells
- Found in early human embryos - ability to turn into any cell
- Found in bone marrow in humans
- Used in medicine or research
- To replace faulty cells
- Therapeutic cloning - embryo made to have same genetic info as patient - not rejected
- Risks involve contamination with virus
- Some against it for religous & ethical reasons
- Can produce identical plants - meristem
Chromosomes & Mitosis & The Cell Cycle
- Coiled up DNA - contains genes
- Body cells divide
- Multicellular organisms use mitosis to grow, develop & replace cells.
- Cell increases amount of subcellular structures & DNA duplicated - chromosomes pulled apart - nucleus divides - produces 2 new identical daughter cells.
Diffusion
- Particles moving from area of higher concentration to low concentration
- In solutions & gases
- Bigger the concentration gradient, faster rate of diffusion
- Larger the surface area of the membrane - faster rate of diffusion - more particles mass through at once.
Osmosis
- Movement of water particles from higher water concentration to lower water concentration.
- Water molecules move randomly
- Passive Movement
Osmosis Required Practical
- Cut potato into cyclinders
- Have beakers with different concentrated sugar solutions & one with water in it
- Measure mass of cylinders & add each one to a beaker
- Leave for 24 hours
- Dry them & measure mass again
- if drawn in water - increase in mass
- if water drawn out - decrease in mass
Active Transport
- Low to high concentration
- Root hair cells take in minerals using active transport
- Used in gut when there is low concentration of nutrients in the gut but higher concentration of nutrients in the blood
Exchanging Substances
- Larger the organism the smaller its surface area compared to its volume
- Thin Membrane - short distance to diffuse
- Large surface area
- Lots of blood vessels in animals
- Ventilated
Examples of Exchange Substances
Gas Exchange in Lungs - transfer oxygen to blood & remove CO2 - contain alveoli - maximise diffusion - large surface area - moist lining - thin walls - good blood supply
Villi - large surface area - inside small intestine - digested food absorbed quickly - single layer of surface cells - good blood supply.
Structure of Leaves - Stomata (exchange surface) - CO2 diffuses in - O2 diffuses out - size of stomata controlled by guard cells - flat shape of leaf increases area
Gills - Large SA - lamallae - blood capillaries to speed up diffusion - thin surface layer - less distance
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