Cell Structure

History of the Cell - Scientist were aware of cells only after the discovery of microscopes.. “Guys” who contributed to cell theory: •Hooke 1665 – coined term ‘cell’ •Van Leeuwenhoek – v

Cell Structure

History of the Cell - Scientist were aware of

cells only after the discovery of microscopes.

“Guys” who contributed to cell theory:

•Hooke (1665) – coined term ‘cell’

•Van Leeuwenhoek – viewed first living cells

•Schleiden (1838) – plants are composed of cells

•Schwann (1839) – animals are composed of cells

•Virchow (1858) – cells come from cells

Cell theory which states:

1 All living things are composed of one

or more cells

2 In organisms, cells are the basic units

of structure and function

3 Cells are produced only from existing

cells

ALL cells share certain structural

characteristics:

1 Cell or Plasma membrane

2 Cytoplasm

3 Genetic Material

1 Cell or plasma membrane –

•Composed of lipid bilayer and

proteins.

•Separates the cell contents from

materials outside the cell

•Regulates what enters and leaves the

cell, maintaining homeostasis; called selectively permeable.

Cell Membrane

2 Cytoplasm – gel-like substance that

suspends organelles and contains sugars,

amino acids, and proteins

•Contains Organelles –

membrane-bound internal compartments that carry out specific functions

•Contains free-floating ribosomes.

Site of protein synthesis (where proteins are made)

Not considered organelles because they have no membranes surrounding them

Ribosomes: the little black dots!

Genetic material:

•Composed of DNA

•Controls reproduction of cell, contains hereditary

information, and carries out the day-to-day cellular activities.

•In eukaryotic cells, DNA surrounded by a double

membrane (nuclear membrane) is the Nucleus.

•Nuclear membrane is passageway for RNA and

ribosome subunits.

•Nucleus contains chromosomes (DNA

super-wound around histone proteins into highly

condensed form)

•Nucleolus – where ribosome subunits are made.

Plant nucleus

Nuclear membrane and pores

DNA: chromatin

Nucleolus

The Interior of a Cell:

Internal Membranes (double layer of lipids):

1 Endoplasmic reticulum (ER)

• Series of channels that weave through the

cell transporting substances made by the

cell

• Isolated spaces of ER forming sacs are

called vesicles

a Rough ER – ER that contains ribosomes

on the outside and carry proteins

b Smooth ER – ER with no ribosomes on

the outside and carry lipids

Rough ER

Sorry, no pictures

of smooth ER.

Vesicles

2 Golgi apparatus (bodies) – collect,

package, and distribute molecules made

in the cell

Golgi bodies

1 Mitochondria

• Contains folded membranes called

cristae (increases surface area)

• Generate energy for the cell through

cellular respiration

2 Chloroplast:

• Consist of stacks of membranes called

grana surrounded by liquid called stroma.

• Sites of photosynthesis (make food in

form of sugar) in plants and algae

Chloroplasts

Central Vacuole

Grana Stroma

Biochemical factories - membrane-bound spheres

• Contain digestive enzymes to breakdown

proteins, nucleic acids, lipids, and carbohydrates

• Digest and recycle the cell’s used component

Lysosome

2 Flagella – long, whip-like tail used for

locomotion

3 Cilia – shorter, more numerous hairs cell

4 Centrioles – associated with microtubules

that move chromosomes during cell

division

B Microfilaments – protein fibers called

actin and myosin; used in muscle contraction

Central vacuole

•Found in plant cell

•Contains large amounts of water along with

sugars, ions, and pigments

•Provides rigidity in plant cell (acts as

“skeleton”)

Central Vacuole

Plant Cell Animal Cell

Contains cell membrane Contains cell membrane

numerous vacuoles