Overview
This lecture covers the structure, function, and specialization of cells, how cells divide and are cultured, and how substances are transported across cell membranes.
Cell Structure
- All living organisms are made of cells, which perform specific functions based on their structure.
- Eukaryotic cells (plants and animals) have a nucleus, cytoplasm, and cell membrane; plant cells also have cell walls, chloroplasts, and vacuoles.
- Prokaryotic cells (bacteria) are smaller, lack a nucleus, and have DNA in loops and plasmids.
- Students should understand the scale of cells and use standard form for measurements.
Animal and Plant Cells
- Animal cells contain nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.
- Plant cells contain all animal cell structures plus chloroplasts, a permanent vacuole, and a cellulose cell wall.
- Estimations and diagrams are used to compare and interpret cell structures.
Cell Specialisation and Differentiation
- Cells are specialized to perform particular functions (e.g., sperm, nerve, muscle, root hair, xylem, phloem).
- Differentiation forms various cell types; most animal cells differentiate early, while many plant cells can differentiate throughout life.
- Specialized cells acquire features to help them fulfill specific roles.
Microscopy
- Light and electron microscopes are used to study cells; electron microscopes offer higher magnification and resolution.
- Understanding of sub-cellular structures has increased with electron microscopy.
- Use the formula: magnification = size of image / size of real object (express in standard form if needed).
Culturing Microorganisms
- Bacteria multiply by binary fission, forming colonies in nutrient broth or agar plates.
- Cultures must be uncontaminated using aseptic techniques (sterilization, tape-sealing, incubation below 25°C).
- Calculate bacterial population growth and colony areas using relevant formulas.
Chromosomes, Mitosis, and Cell Cycle
- Chromosomes made of DNA carry genes; body cells have chromosomes in pairs.
- Cell cycle: cells grow, replicate DNA, and divide by mitosis to produce two identical cells.
- Mitosis is essential for growth and repair of multicellular organisms.
Stem Cells
- Stem cells are undifferentiated and can give rise to many cell types.
- Embryonic stem cells can form most cell types; adult stem cells (e.g., bone marrow) form some cell types.
- Plant meristems remain able to differentiate throughout the plant’s life.
- Stem cells can repair tissue and clone plants; their use has ethical and medical considerations.
Transport in Cells
- Diffusion is movement from high to low concentration; rate affected by concentration gradient, temperature, and surface area.
- Osmosis is diffusion of water through a partially permeable membrane from dilute to concentrated solutions.
- Active transport moves substances against concentration gradients, requiring energy.
- Multicellular organisms need specialized exchange surfaces to meet cellular demands.
Key Terms & Definitions
- Eukaryote — Cell with a nucleus and membrane-bound organelles.
- Prokaryote — Cell without a nucleus; DNA is in loops and plasmids.
- Differentiation — Process by which cells become specialized.
- Mitosis — Division of a cell to form two identical daughter cells.
- Stem Cell — Undifferentiated cell capable of becoming various cell types.
- Diffusion — Movement of particles from high to low concentration.
- Osmosis — Movement of water from dilute to concentrated solutions through a partially permeable membrane.
- Active Transport — Movement of substances against a concentration gradient using energy.
Action Items / Next Steps
- Use a light microscope to observe, draw, and label plant and animal cells, including a magnification scale.
- Investigate effects of antiseptics or antibiotics on bacterial growth using agar plates.
- Investigate osmosis in plant tissue using various salt or sugar concentrations.
- Practice calculating magnification, population growth, and surface area to volume ratios.