Year 3 Biology Notes: Cell Structure and Organisation

B1

Learning Outcomes for Year 3 Biology

Topic B1: Cell Structure and Organisation

This section focuses on understanding cell structures and their functions through observation and analysis of plant and animal cells.

1. Key Cell Structures in Plant and Animal Cells

(a) Identification and Functions

  • Cell Wall

  • Function: Provides structure and protection to plant cells; made up of cellulose.

  • Cell Surface Membrane

  • Function: Regulates what enters and exits the cell; semi-permeable.

  • Cytoplasm

  • Function: Gel-like fluid where organelles are suspended; site for metabolic processes.

  • Nucleus

  • Function: Control center of the cell; contains DNA and is responsible for gene expression and replication.

  • Cell Vacuoles

  • Plant Cells: Large, sap-filled for storage and maintaining turgor pressure.

  • Animal Cells: Small, temporary storage for waste or nutrients.

  • Chloroplasts

  • Function: Site of photosynthesis in plant cells, contains chlorophyll.

2. Membrane Systems and Organelles

(b) Identification and Functions

  • Endoplasmic Reticulum (ER)

  • Function: Synthesizes proteins (rough ER with ribosomes) and lipids (smooth ER).

  • Golgi Body

  • Function: Modifies, sorts, and packages proteins for secretion or delivery to other organelles.

  • Mitochondria

  • Function: Powerhouse of the cell; site of cellular respiration to produce ATP (energy).

  • Ribosomes

  • Function: Protein synthesis; can be found free in cytoplasm or attached to the ER.

3. Comparison of Plant and Animal Cells

(c) Structural Differences

  • Cell Wall vs. Cell Membrane:

  • Plant cells have a rigid cell wall; animal cells only have a flexible cell membrane.

  • Chloroplasts:

  • Present in plant cells for photosynthesis; absent in animal cells.

  • Vacuoles:

  • Large central vacuole in plants; smaller and more numerous in animals.

4. Adaptation of Specialized Cells

(d) Examples of Structure-Function Relationships

  • Muscle Cells:

  • Adaptation: Numerous mitochondria to meet high energy demand for contraction.

  • Root Hair Cells:

  • Adaptation: Large surface area to maximize absorption of water and nutrients from soil.

  • Red Blood Cells:

  • Adaptation: Lack of nucleus to allow more space for hemoglobin, enhancing oxygen transport efficiency.

5. Application

(e) Using Knowledge in New Situations

  • Apply the understanding of cell structures to solve biological problems, for example