BiologyUNIT 5- CELLS

History of Cell Theory

Until the invention of microscopes, scientists did not

know the world of microorganisms that existed.

This research was pioneered by Anton Van

Leeuwenhoek in the 1600’s.

We now have compound light microscopes which can

magnify objects up to 1500 times.

The History of Cell Theory

Robert Hooke also studied in the 1600’s

Studied oak bark and found many small

compartments.

Named the compartments cells after the rooms monks

lived in.

Parts of the Cell Theory

All organisms are made of one or more cells.

The cell is the basic unit for structure of living things.

All cells come from pre-existing cells.

Electron Microscopes

Electron microscopes use a beam of electrons to

magnify objects up to 500,000 times.

2 Cell Types

Prokaryote

Mostly unicellular

No organelles

Circular DNA

Smaller of the 2

Eukaryote

Mostly Multi-cellular

Membrane bound organelles

DNA contained in Nucleus

Larger of the 2

Plasma Membrane

Cells need nutrients and it is the job of the plasma

membrane to allow these nutrients to come into the

cell.

This is done through selective permeability.

Selective permeability allows some molecules to come

in while leaving others out.

Structure of the Plasma Membrane

Made of a phospholipids.

In a phospholipid, a fatty acid is replaced by a

phosphate.

Phospholipids form 2 layers

Phospholipid Bilayer

Phosphate is polar while the lipid sections are nonpolar.

The polar phosphate is what lets water in and out of the

cell.

Because the non-polar lipids do not like water, they fold

to the inside of the membrane.

Cell Barriers

Cell walls: Rigid layer outside plasma membrane.

Provide extra support and structure.

Not found on animal cells.

Organelles for Cell Control

Nucleus: Contains chromatin, where the strands of DNA

are kept. Also bound in a membrane.

Nucleolus: Inside nucleus, makes ribosomes.

Ribosomes: Organelles that use directions from DNA to

make protein.

Cytoplasm: Clear, gelatinous fluid inside a cell. Allows

for transport within the cell.

Organelles for Assembly and Transport

Endoplasmic Reticulum (ER): Site of cellular chemical

reactions, most importantly protein synthesis.

Rough: Ribosomes attached

Smooth: No ribosomes attached

Golgi Body: (Cellular UPS) Packs newly made proteins

into packages called vesicles, to be sent to the

appropriate location in the cell.

Organelles for Storage

Vacuole: Membrane bound compartments for

temporary storage of materials.

Store food, enzymes, and other materials needed by a

cell.

Lysosomes: Organelles that contain digestive enzymes.

Digest worn out organelles, food particles, bacteria or

viruses.

Organelles Used for Energy

Chloroplasts: Used in plants and green algae to

capture light energy and turn it into sugar.

Mitochondria: Places where cellular respiration takes

place.

Produces ATP (cellular energy)

Support and Locomotion

Cytoskeleton: Support structure within the cytoplasm.

Cilia: Hair-like projections used for locomotion.

Flagella: Whip-like projections used for locomotion.