Cells

Some Random Cell Facts

• The average human being is composed of around 100 Trillion individual cells!!!

• It would take as many as 50 cells to cover the area of a dot on the letter “i”

Discovery of Cells• 1665 Robert Hooke

– discovered cells while looking at a thin slice of cork.– described the cells as tiny boxes or a honeycomb– thought that cells only existed in plants and fungi

Anton van Leuwenhoek

• 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms

• He called them “animalcules”

• He also observed blood cells from fish, birds, frogs, dogs, and humans

• Therefore, it was known that cells are found in animals as well as plants

• 1838 Matthias Schleiden– concluded that all plant parts are made of

cells

• 1839 Theodor Schwann, – stated that all animal tissues are composed of

cells.

• 1858- Rudolf Virchow– concluded that cells must arise from preexisting cells.

The Cell Theory Complete

• The 3 Basic Components of the Cell Theory were now complete:

1. All organisms are composed of one or more cells.

2. The cell is the basic unit of life in all living things.

3. All cells are produced by the division of preexisting cells.

Can you design the “best cell” shape?

• What do cells need?

• How could you measure if this need is met?

• How could you compare different designs?

2 Basic Types of Cells1) Prokaryotic examples ???2) Eukaryotic examples????

Plasma membrane• Structure

– Main component is phospholipids that are arranged in a double layer (bilayer)

– Has scattered proteins within the phospholipids

Function of the Plasma Membrane

• Regulate what gets into or leaves the cell

Nucleus• Structure

– Surrounded by a double membrane

– This “nuclear membrane” has pores

• Function– Holds the

chromosomes (DNA) and the nucleolus

Nuclear envelope

• Double layer of membrane

• Has pores

• Surrounds the nucleus

• Regulates what goes into and out of the nucleus

Chromosomes

• Structure– String-like

structures in the nucleus made of DNA and protein

• Function – Contain your genes

Nucleolus • Structure

– Small dark structure in the nucleus

• Function– Produce ribosomes

Ribosomes

• Small structures (NOT made of membrane)

• Make proteins

Central Vacuole

• Structure– LARGE sac made

of membrane– Found in center of

plant cells

• Function– Stores chemicals

and water

Smooth Endoplasmic Reticulum• Structure

– Canals and tubes made of membrane

• Function– Makes lipids (oils,

phospholipids, steroids)

– Detoxifies poisons

Rough Endoplasmic Reticulum

• Structure– Canals and tubes

made of membrane– Have ribosomes

attached to the outside

• Function– Transport materials

in the cell– Make proteins

(those exported from the cell, those found on the plasma membrane, those found in lysosomes)

Golgi Apparatus• Structure

– Stacks of membrane sacs

– has a receiving end (from ER) and a shipping end

• Function– Chemically modifies

substances– Packages material for

transport out of the cell or to other locations within the cell

Vesicles • Structure

– Small membrane “bubbles” that bud off the ER or Golgi

• Functions– Transport materials

to new locations

Lysosomes • Structure

– Sacs of membrane that contain hydrolytic enzymes

– -found mostly in animal cells

• Function– Use enzymes to

break down old organelles

– In white blood cells are used to destroy bacteria

Mitochondria

• Structure– Surrounded by a

double membrane• Folds found on the

inside

• Function– Cellular Respiration

• Converts energy in sugars into the energy of ATP molecule

Chloroplasts

• Structure– Surrounded by a

double layer of membrane

• Disks found inside

• Function – Convert solar

energy into chemical energy (food)

– Site of photosynthesis

Perioxisome • Structure

– Small membranous sac

• Function – Some reactions

occurring here produce H2O2 (toxic)

• So, it also contains an enzyme (catalase) that converts this to water and oxygen gas

Cell Wall• Structure

– Found outside the plasma membrane

– Plant made of cellulose

• Function– Give support to

certain cells (plant)– Does NOT

determine what can get into/out of the cell

Cytoskeleton

• Structure• Made of protein fibers

– Microtubules• Hollow tube

– Microfilaments• Small rods

– Intermediate filaments

• Function– Give the cell shape– Help to move

organelles around the cell

Fig. 4-17

Microfilament

Actin subunit

7 nm

Intermediate filament

Fibrous subunits

10 nm

Microtubule

Tubulin subunit

25 nm

Nucleus

Nucleus

Centrioles

• Structure– Made of rings of

microtubules– Found in pairs that

lie at right angles • Look similar to a

pair of barrels

• Function– Found in animal

cells– Help organize the

tubulin required for cell division

Cilia• Structure

– Microtubules that extend from the cell (still covered by the plasma membrane)

– Short and many of them

• Function– In single-celled

organisms, they can move the organism from place to place

– If anchored in place, can set up a current, moving fluid across the surface of a cell

Fig. 4-1c

Fig. 4-18a

Cilia

http://www.youtube.com/watch?v=YHb2JaujIPo&feature=related&safety_mode=true&persist_safety_mode=1

Flagella Structure • Same as cilia, but

are longer and there are just a few of them

• Prokaryotes also have them– Not made of

microtubules

Function • Move the cell within its

environment

Fig. 4-20

EXTRACELLULAR FLUID

Microfilaments

Collagen fiber

Connectingglycoprotein

Integrin

Plasmamembrane

Glycoproteincomplex with longpolysaccharide

CYTOPLASM

How large can cells get?-depends on how efficiently they can get nutrients in and wastes out

30 µm

30 µm 10 µm

10 µm

Surface areaof one large cube= 5,400 µm2

Total surface areaof 27 small cubes= 16,200 µm2

Fig. 4-21

Tight junctions

Anchoring junction

Gap junctions

Plasma membranesof adjacent cells

Extracellular matrix

Fig. 4-22

Vacuole

Wallsof twoadjacentplant cells

Cytoplasm

Plasma membrane

Plasmodesmata

cell wall

A

BE

CD (CONTAINING DIGESTIVE ENZYMES)

AC

AD

C

D

E

AB

BD

B

AEBC

A

B

C

E

AB

AC

AD

AE

BC

BD

BE

D

A

B

C

D