Cell Theory : Unit 1 Cell Structure (Chapter 4)

Unified Cell Theory

Principle	Meaning
All organisms are made of cells	Cells form the structure of life
The cell is the basic unit of life	Smallest living unit
All cells come from pre‑existing cells	Explains growth and reproduction
Cells carry genetic material	DNA passes information to new cells

Shared by ALL cells (1/4)

Plasma membrane : Controls movement in/out of cell

Shared by ALL cells (2/4)

Cytoplasm : Site of reactions; holds structures

Shared by ALL cells (3/4)

DNA/RNA : Stores and transmits genetic info

Shared by ALL cells (4/4)

Ribosomes : Make proteins

Prokaryotic VS Eukaryotic (1/6)

Nucleus

Pro: ❌ None

Euk: ✔ Present

Prokaryotic VS Eukaryotic (2/6)

Organelles

Pro: ❌ None

Euk: ✔ Many

Prokaryotic VS Eukaryotic (3/6)

Size

Pro: Small

Euk: Larger

Prokaryotic VS Eukaryotic (4/6)

DNA

Pro: Circular

Euk: Linear

Prokaryotic VS Eukaryotic (5/6)

Complexity

Pro: Simple

Euk: Complex

Prokaryotic VS Eukaryotic (6/6)

Examples

Pro: Bacteria, Archaea

Euk: Plants, Animals, Fungi, Protists

Desmosomes

Found in: Animals

Function: Strong adhesion; prevents tearing

Tight Junctions

Found in: Animals

Function: Seal spaces; prevent leakage

Gap Junctions

Found in: Animals

Function: Communication channels

Plasmodesmata

Found in: Plants

Function: Cytoplasmic bridges through cell walls

Cells are so SMALL, why?

1. High surface‑area‑to‑volume ratio → efficient exchange

2. Fast internal communication

3. Efficient cell division

Viruses

Typical Size: 20–300 nm

Relative Size: Smallest

Prokaryotic Cells

Typical Size: 1–10 µm

Relative Size: Medium 

Eukaryotic Cells

Typical Size: 10–100 µm

Relative Size: Largest

Plant Cell VS Animal Cell (1/7)

Cell Wall

P: ✔ Present

A: ❌ Absent

Plant Cell VS Animal Cell (2/7)

Chloroplasts

P: ✔ Present

A: ❌ Absent

Plant Cell VS Animal Cell (3/7)

Large Central Vacuole

P: ✔ Present

A: ❌ Absent

Plant Cell VS Animal Cell (4/7)

Shape

P: Boxy/rectangular

A: Round/irregular

Plant Cell VS Animal Cell (5/7)

Lysosomes

P: Rare

A: ✔ Common

Plant Cell VS Animal Cell (6/7)

Centrioles

P: ❌ Absent

A: ✔ Present

Plant Cell VS Animal Cell (7/7)

Photosynthesis

P: ✔ Yes

A: ❌ No