What are Cells?

• Cells are the basic unit of life.

• All living organisms consist of cells.

  • Examples: Bacteria, human cells.

Types of Cells

Unicellular Organism

• Definition: Organisms comprised of a single cell.

• Examples:

  • Bacteria

  • Paramecium

  • Amoeba

  • Chlamydomonas

  • Yeast

• Characteristics:

  • Can survive in extreme environments (hot or cold).

Multicellular Organism

• Definition: Organisms consisting of multiple cells.

• Examples:

  • Humans

  • Fish

  • Trees

  • Fungi

• Characteristics:

  • Typically composed of two or more cells.

Animal Cells

• Characteristics:

  • Varied shapes, functions, and sizes.

  • Grouped into tissues, which perform specific functions together to form organs.

Human Cells and Functions

• Red Blood Cell:

  • Function: Transports oxygen, digested food, and carbon dioxide in the bloodstream.

  • Feature: Lacks a nucleus.

• Nerve Cell:

  • Function: Transmits signals related to pain and other stimuli throughout the body.

• Egg Cell:

  • Feature: Largest cell in the body; involved in reproduction (female).

• Sperm Cell:

  • Feature: Smallest cell in the body; involved in reproduction (male).

Plant Cells

• Characteristics:

  • Have diverse shapes, functions, and sizes based on their location in the plant.

Plant Cells and Functions

• Leaf Cell:

  • Contains chlorophyll; operates photosynthesis by trapping sunlight to produce food.

• Guard Cells:

  • Location: Found primarily on the underside of leaves.

  • Function: Regulate the size of stomata for gas exchange.

• Root Cell:

  • Function: Absorbs water and minerals; lacks chloroplasts but has a cell wall.

Parts of an Animal Cell and a Plant Cell

Common Cell Parts

1. Cell Membrane: Encloses the cytoplasm; regulates substance movement.

2. Cytoplasm: Jelly-like fluid containing cell parts; maintains shape.

3. Nucleus: Control center, containing genetic information.

4. Vacuole: Liquid-filled sac for storing nutrients and waste products.

5. Cell Wall: (only in plant cells) Supports structure and shape.

6. Chloroplast: (only in plant cells) Contains chlorophyll for photosynthesis.

Cell Division and Reproduction

• Cells, being living entities, undergo aging and can die.

• New cells are produced through a process called cell division.

Using a Microscope

• Cells are microscopic; microscopes are essential to observe them, such as bacteria and other microorganisms.

Recap Questions

• List 2 examples of unicellular organisms: Yeast, Bacterium.

• List 1 example of a multicellular organism: Human.

• Define tissue.

• Name the largest human cell: Egg cell.

• List parts of animal and plant cells: Cytoplasm, Nucleus, Cell Membrane, Vacuole, Cell Wall, Chloroplast.

• Do root cells contain chloroplasts? No, they do not require photosynthesis.

• What is the term for the production of new cells? Cell division.

Practice Questions

MCQ: Classify plant cell types

• Given: Cell membrane, chloroplast, cell wall.

• Which classification is correct for the cells P, Q, and R?

  • Plant Cell: (1) Q only; (2) P and Q only; (3) Q and R only; (4) P, Q, and R.

Flowchart Activity: Cell Classification

• Using characteristics (e.g., cell wall, nucleus, chloroplasts) to identify cell types based on provided letters (J, K, L, M).