cells and the cell theory

Objectives• List scientists who contributed to the cell theory• List the components of the cell theory• Compare prokaryote and eukaryote cells• Label a plant and an animal cell• Know the functions of cell organelles

Early Contributions• Robert Hooke - First person to see cells, he was

looking at cork and noted that he saw "a great many boxes. (1665)

• Anton van Leeuwenhoek - Observed living cells in pond water, which he called "animalcules" (1673)

• Theodore Schwann - zoologist who observed tissues of animals had cells (1839)

• Mattias Schleiden - botanist, observed tissues of plants contained cells ( 1845)

• Rudolf Virchow - also reported that every living thing is made of up vital units, known as cells. He predicted that cells come from other cells. (1850 )

The Cell Theory• 1. Every living

organism is made of one or more cells.

• 2. The cell is the basic unit of structure and function.

• 3. It is the smallest unit that can perform life functions.

• 4. All cells arise from pre-existing cells.

*Why is the Cell Theory called a Theory and not a Fact?

Cell FeaturesALL cells have these parts• Ribosomes – make protein for use by the

organism• Cytoplasm – fluid material within  cell• DNA – genetic material• Cytoskeleton – internal framework of cell• Cell Membrane – outer boundary, some things

can cross the cell membrane

Comprehension Checkpoint

Answer true or false

1.Robert Hooke was the first person to see cells.2.Bacteria cells have a cell membrane.3.The Cell Theory was developed by a single

scientist.4.Plant cells have cytoplasm.5.Cells taken from fungi do not have DNA.6.Cells can only come from pre-existing cells.

Prokaryote Cells• The first cells to inhabit the earth• Simple cells• Bacteria• These cells do NOT have a nucleus, their DNA is

circular and floats in the cytoplasm

Some bacteria have a tail-like structure called a flagella, that helps it to move.

A capsule surrounds some bacteria and helps them avoid the body’s immune system

Bacteria-prokaryotic

Bacteria that causes Anthrax

Eukaryotic Cells• Cells found in plants, animals, protists,

and fungi • The cell is composed of 4 main parts:

1.Cell membrane2.Cytoplasm3.Nucleus – “control center” of cell, houses DNA4.Organelles – small structures that carry out

specific functions (“little organs”)

Nucleus• Usually found at center of cell• Has a nuclear membrane & nuclear pores•  Contains cell’s DNA in one of 2 forms

o chromatin - DNA bound to protein (non-dividing cell)

o chromosomes - condensed structures seen in a dividing cell (look like Xs)

•  Also contains an organelle called nucleolus - which makes the cell’s ribosomes

Cell Organelles

Mitochondria – this is the cell’s energy center. It turns food into a chemical energy called ATP.The mitochondria is sometimes called the “powerhouse” of the cell.

Cell Organelles

Golgi Apparatus – processes, packages and secretes proteins. It is comparable to a factory or a post office.

*A vesicle is used with the Golgi to transport substances outside cell, like a messenger delivering a package.  

Cell Organelles

Lysosome – Contains digestive enzymes, breaks things down, "suicide sac”

Endoplasmic Reticulum – Transport, "intracellular highway".  -Rough ER contains many ribosomes & is involved in protein synthesis -Smooth ER ribosomes not found on surface

Cell OrganellesCytoskeleton – Helps cell maintain support & shape; movementa. microtubules-hollow structures; also help build cilia  flagellab.  microfilaments-threadlikec.  centrioles-only in animal cells; used during cell division (paired) 

Vacuole – storage area for water and other substaces, plant cells usually have a large central vacuole

Protein ProductionThe cell is like a factory. Its product is protein which goes to body to serve different functions.1.DNA has instructions to build protein2.These instructions are sent to ribosomes3.The ribosomes build protein and send it through ER4.The proteins are delivered to golgi where they are

completed and “tagged” for export outside cell

THE ANIMAL CELL

Cheek Cells Seen Through Microscope

Plant Cells• Have additional structures• CELL WALL – surrounds membrane & provides

additional support• CHLOROPLASTS – contain green pigment,

function in photosynthesis• CENTRAL VACUOLE – large water container

in center of cell

PLANT CELL

Can you identify the parts?

Anacharis Cells Viewed With a Microscope

Organelles With DNA• Mitochondria and chloroplasts have their own DNA

(separate from the nucleus)• This supports the ENDOSYMBIOSIS THEORY which

states that eukaryotic cells evolved when prokaryote cells engulfed or absorbed other cells.

CELL MEMBRANE• Selectively permeable; it regulates what comes into

the cell and what leaves the cell• It is composed of a double layer of phospholipids

with proteins embedded throughout