Cell Structure and Transport

Cell Structure and Transport

Microscopy

  • Light Microscopes: Use light and lenses; magnification up to 1’000x, resolution limited to ~200 nm.

  • Electron Microscopes: Use electrons; magnification of up to 1 million times, resolution of ~0.1 nm. Enables detailed study of subcellular structures.

Calculation of Magnification

  • Formula: magnification = image size / real size.

  • Rearranged formulas: real size = image size / magnification , image size = magnification x real size.

Advantages and Disadvantages of Microscopes

  • Light Microscope: Easy to use, inexpensive; limited resolution.

  • Electron Microscope: Higher resolution; hard to use, expensive.

Animal and Plant Cells

Cell Structure

  • Animal Cells: Cell membrane, nucleus, cytoplasm, mitochondria, ribosomes.

  • Plant Cells: All animal cell structures + cell wall (cellulose), vacuole, chloroplasts (contain chlorophyll).

  • Bacterial Cells: Prokaryotic; have cell wall, cell membrane, cytoplasm, ribosomes, flagella, circular DNA.

Functions of Key Organelles

  • Cell Membrane: Controls entry/exit of substances.

  • Nucleus: Contains genetic material, directs cell activities.

  • Mitochondria: Site of aerobic respiration, energy production.

  • Ribosomes: Site of protein synthesis.

  • Chloroplasts: Site of photosynthesis (plants only).

Differences: Prokaryotic vs Eukaryotic Cells

  • Prokaryotic: Smaller (0.2 - 2.0 μm), no nucleus, cell division via binary fission.

  • Eukaryotic: Larger (5 - 100 μm), true nucleus, cell division via mitosis.

Specialization in Animal and Plant Cells

Animal Cells

  • Sperm Cell: Streamlined structure, flagellum, high mitochondria for energy.

  • Nerve Cell: nucleus to contain genetic information ,branched connections, long to cover more distance.

  • Muscle Cell: Long and packed with mitochondria for contracting.

  • Red Blood Cell: Large surface area, no nucleus for oxygen transport, contains haemoglobin.

  • White Blood Cell: Flexible shape, lobed nucleus for immune response.

Plant Cells

  • Root Hair Cells: hairs Increase surface area for water and mineral absorption, lots of mitochondria for active transport.

  • Palisade Cells: Lots of chloroplasts for photosynthesis, towards top of leaves for max light.

  • Xylem Cells: Thick walls for support, hollow tubes for water transport.

  • Phloem Cells: Transport sugars, few organelles for smooth flow, companion cells have lots of mitochondria to transport substances

Diffusion and Osmosis

Diffusion

  • The movement of particles from high to low concentration until equilibrium is reached, through a partially permeable membrane.

  • Factors affecting diffusion: concentration gradient, temperature, surface area.

Osmosis

  • Movement of water molecules through a partially permeable membrane from high to low water concentration.

  • Important for maintaining cell functions and blood pressure.

  • If animals lose or gain too much water, their cells can stop working properly

  • Essential for : water balance, waste removal, blood pressure, cell size

Plant Osmosis

  • Turgidity: Water movement into cells; plants remain firm.

  • Plasmolysis: Water loss causes cell contents to shrink, leading to wilting.

Active Transport

  • Movement against the concentration gradient (low to high) across a membrane

  • Requires energy; examples include nutrient uptake in roots and glucose absorption in the gut.

Exchange Surfaces

  • Optimized for effective material exchange:

    • Large surface area

    • Thin membranes

    • Good blood supply

  • Necessary for multicellular organisms to meet metabolic demands due to smaller surface area to volume ratio compared to single-celled organisms.