Cells, Tissues, Organs, and Systems Vocabulary

The Cell as the Basic Unit of Life

• Learning intention: Describe the cell as the basic unit of all living things.
• Living things get energy from the sun (plants - photosynthesis) or by consuming other organisms (animals).
• MRS GREN: Living characteristics (Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition).

Cell Theory

• Cell Theory: All organisms are composed of one or more cells; the cell is the basic unit of structure and organization in organisms; all cells come from pre-existing cells.
• Anton van Leeuwenhoek discovered bacteria.
• Robert Hooke named the cell.
• Theodor Schwann realized all animals are made of cells.

Scientific Investigation: Sensitivity of the Skin

• Scientific Question: Which part of the arm is the most sensitive?
• Independent Variable: Part of the arm.
• Dependent Variable: Number of points felt correctly.
• Control Variable: Same type of wire, same person.

Using a Microscope

• To see cells in detail, a microscope is needed to magnify the object.
• Key parts of a microscope:
  • Eyepiece lens: To observe your specimen(cell).
  • Coarse adjustment knob: To move the stage up and down.
  • Fine adjustment knob: To sharpen/unblur the image.
  • Base: To support the whole microscope.
  • Objective lens: To magnify the image.
  • Stage: Place the glass slide on it.
  • Diaphragm: To control the brightness of the light.
  • Light Source: Light shines onto specimen.

Viewing Cells Under a Microscope

• Onion Cell Preparation: Use a knife to cut the onion -> Proceed with using a scalpel to obtain a thin layer -> Place the thin layer (specimen) on the glass slide -> Add 2 - 3 drops of iodine and cover the specimen with a cover slip -> Place the glass slide onto the lowered stage and start with the lowest magnification.
• Cheek Cell Preparation: Gently scrape the inside of your mouth with a toothpick -> Smear the toothpick on the center of the glass slide -> Add 1 - 2 drops of methylene blue and cover the specimen with a cover slip -> Remove any excess liquid with a paper towel -> Place the glass slide onto the lowered stage and start with the lowest magnification.
• Safety rules include gently scraping cheeks, throwing toothpicks immediately, and using low concentration of methylene blue.

Cell Organelles and Their Functions

• Key organelles: nucleus, cytoplasm, cell membrane, cell wall, chloroplast, sap vacuole, mitochondria.
• Functions:
  • Nucleus: Control center of the cell.
  • Cytoplasm: Gel-like substance where organelles are located.
  • Cell membrane: Outer boundary of the cell.
  • Mitochondria: Powerhouse of the cell, respiration occurs here.
  • Cell Wall: Provides support and protection (plant cells only).
  • Chloroplast: Site of photosynthesis (plant cells only).
  • Vacuole: Storage of water and nutrients.

Specialised Cells

• Specialised cells have specific features to perform particular functions.
• Examples:
  • Red blood cells: Carry oxygen, disc-like shape, no nucleus.
  • Neurones: Transmit electrical impulses, long and thin.
  • Ciliated cells: Use cilia for movement.
  • Root hair cells: Absorb water, large surface area.
  • Palisade cells: Photosynthesis, contain chloroplasts.

Levels of Organisation

• Hierarchy of organisation: Cell -> Tissue -> Organ -> Organ System -> Organism
• Definitions:
  • Cell: Basic unit of life.
  • Tissue: Group of cells.
  • Organ: Group of different tissues working together.
  • Organ System: Group of different organs.
  • Organism: A group of organ systems.

Unicellular Organisms

• Multicellular: An organism that has more than one cell.
• Unicellular: An organism that has only one cell.
• Amoeba: Shares similarities with animal cells; eats by engulfing food.