2.1The Structure & Functions of

Eukaryotic Cells

Cells

• Smallest living unit• Most are microscopic

Defining a Cell

• A cell is a confined system of potentially self perpetuating linked organic reactions that are catalyzed step-wise by enzymes.

Principles of The Cell Theory

• All living things are made of 1 or more cells

• Smallest living unit of structure and function of all organisms is the cell

• All cells arise from pre-existing cells

(this principle discarded the idea of

spontaneous generation)

Cell Size

Small Cells have a large Surface Area-to-Volume Ratio. Why?

Why are S.A./Vol. Ratios Important?

• Surface area represents the “access” available to and from a cell for supplies.

• Volume represents how much has to be supplied.

• The more “access” you have to supply each unit of volume, the more efficient the cell is.

Characteristics of Living Cells

• Very complex• Very small• Self-replicating• Autonomous/semiautonomous• Homeostatic

There are 2 Cell Types

• Prokaryotic

• Eukaryotic

Prokaryotic Cells• First cell type on earth

(chemosynthetic)• All are single celled (ie Bacteria)

Prokaryotic Cells

• No membrane bound structures inside• Nucleoid instead of nucleus (region of DNA

concentration).• Organelles not bound by membranes

Eukaryotic Cells

• Internal membrane bound organelles• Cytoplasm (cytosol, organelles +

molecule & ions ) for metabolism• Cell Membrane (Phospholipid bilayer)• Can be Single or Multi-celled

Protozoan

Eukaryotic Animal Cell

Animal Cell Micrograph

Eukaryotic Plant Cell

Plant Cell Micrograph

Cytoplasm

• Viscous fluid containing organelles• components of cytoplasm

– Interconnected protein filaments & fibers – Fluid = cytosol– Organelles (not nucleus)– storage substances

Nucleus • Control center of the cell

• Contains nucleoplasm

• Wrapped by a nuclear envelope which is a double membrane.

• Nuclear pore complexes form openings in nuclear envelope

• Contains

– Chromosomes (DNA)

– Nucleolus

Nucleus Micrograph

Chromosomes (DNA)• Hereditary material• Chromosomes - DNA + proteins

– Short, thick strands– form for cell division

• Chromatin - DNA + proteins

– long, thin strands– form for interphase

• DNA is transcribed & translated into protein to express hereditary traits

Nucleolus

•Non-membrane bound•Contains RNA & proteins•Most cells have 2 or more.•Directs synthesis of RNA•Forms ribosomes

End of Part 1!