Cell biology overview

1. Cell Structure

🔹 Types of Cells:

• Eukaryotic: Animal & Plant cells – have a nucleus.

• Prokaryotic: Bacteria – no nucleus, DNA floats in cytoplasm.

🔹 Animal Cell Structures:

• Nucleus – contains DNA, controls cell activities.

• Cytoplasm – where chemical reactions happen.

• Cell membrane – controls what enters/leaves the cell.

• Mitochondria – respiration happens here.

• Ribosomes – make proteins.

🔹 Plant Cell Structures (in addition to animal):

• Cell wall – made of cellulose, supports cell.

• Permanent vacuole – contains cell sap.

• Chloroplasts – contain chlorophyll for photosynthesis.

🔹 Bacterial Cell Structures (Prokaryote):

• No nucleus – single circular DNA strand.

• Plasmids – small loops of DNA.

• May have flagella for movement.

2. Microscopy

🔹 Types:

• Light microscope – see cells and large organelles.

• Electron microscope – higher resolution, can see smaller things (ribosomes, internal structures of mitochondria).

🔹 Calculations:

• Magnification = Image size ÷ Real size

3. Cell Division

🔹 Chromosomes:

• Found in the nucleus, made of DNA.

• Humans have 46 chromosomes (23 pairs).

🔹 Cell Cycle:

1. Interphase – cell grows, DNA replicates.

2. Mitosis – cell divides to form 2 identical daughter cells.

3. Cytokinesis – cytoplasm and cell membrane divide.

🔹 Importance of Mitosis:

• For growth, repair, asexual reproduction.

4. Stem Cells

🔹 Types:

• Embryonic stem cells – can turn into any cell type.

• Adult stem cells – found in bone marrow, limited use.

• Meristems in plants – can differentiate into any plant cell.

🔹 Uses:

• Treating diseases (e.g. diabetes, paralysis).

• Producing identical plants quickly.

🔹 Issues:

• Ethical concerns.

• Risk of infection and rejection.

5. Transport in Cells

🔹 Diffusion:

• Movement of particles from high to low concentration.

• Happens in gases and liquids.

• Example: oxygen into blood, CO₂ out of cells.

🔹 Osmosis:

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

🔹 Active Transport:

• Movement against concentration gradient.

• Requires energy (from respiration).

• Examples: root hair cells absorbing minerals, sugar absorption in small intestine.

6. Specialised Cells (formed by differentiation)