Chapter 4Structure and

Function

of the Cell!!!Cell - the smallest unit able to carry out all the life activities of an organism.

The History (4-1)The men you need to know about….

• 1500-1600s

• Hans & Zacharias Jenseen – 1st to produce compound microscope

• Robert Hooke -- scientist who saw cork (plant) through microscope and called the openings/pores “CELLS”.

• Anton van Leeuwenhoek –Worked with lenses to create the most powerful microscope up to that time

• Better magnification

• Better resolution

• 1st to observe living cells. (bacteria, protists)

• Known as “Father of Microbiology”

1800s• Schleiden – all plants composed of

cells• Schwann – all animals composed of

cells• Rudolph Virchow – all cells come from

other cells• These three men developed what we

now call the “cell theory”.

CELL THEORY1. All living organisms are composed of one or more cells.

2. Cells are the basic units of structure and function in an organism.

3. Cells come only from the reproduction of existing cells.

Cell Diversity

•Cells come in different shapes, sizes, and internal organizations.

•Shape reflects function.

•Three Domains of Life

•Eukarya

•Bacteria

•Archaea

• TWO BASIC TYPES OF CELLS:

• Eukaryotes

vs. Prokaryotes

Organelles – intracellular bodies that perform specific functions. “mini-organs”

Prokaryotic Cell

• NO membrane bound nucleus• Simple – no membrane bound organelles• Have DNA in “nucleoid” region• Smaller in size• Unicellular• Bacteria• Primitive (old)

Eukaryotic Cell

• A “true” membrane bound NUCLEUS• Complex -many membrane bound

organelles• DNA contained in nucleus• Larger in size• Unicellular and multicellular• Animal, Plants, Fungi, Protist• Not as old as prokaryotes

• Presence of nucleus

• Complexity• Size

What do all cells have?

• Genetic Information• Nucleic Acids –DNA/RNA!• Eukaryotic Cell

– Contained in nucleus– More complex, rod shaped

• Prokaryotic Cell– Free floating– Simple, circular shaped

What do all cells have?

Plasma membrane/cell

membrane • Semi-permeable or Selectively-permeable

• Allows some materials to pass in/out of the cell

• It is composed of phospholipids bilayer. (nonpolar)

• Also has proteins embedded within that act as “bridges” to allow larger materials to pass.

• Covers cell surface, barrier, support, protection

• Phospholipid bilayer behaves like fluid. (called Fluid Mosaic Model)

• The lipids and proteins can move laterally within the bilayer, like boat on ocean.

• Constantly changes

What do all cells have?

• Ribosomes

• Responsible for building protein• Look like small dots. • Some ribosomes are free in

cytoplasm and others attached to “rough” ER.

DNARNAProtein

What do all cells have?Cytoplasm • Region within the plasma

membrane that suspends cell organelles• The “filler”

What do all cells have?• The 4 Macromolecules• Nucleic Acids

– Genetic info

• Proteins– Made by ribosomes (many different functions)

• Lipids– In cell membranes

• Carbohydrates– Energy (metabolism)

Nucleus

• Contains the DNA– Chromatin/chromosomes

• Control center (regulates instructions) Most prominent structure

What makes up the Nucleus?

• Nuclear Envelope• Also called nuclear membrane

• double membrane surrounding nucleus

What makes up the Nucleus?

• Chromosomes• chromatin strands that coil up• Genes • Traits• DNA• “Code”

– ATTTGGCC

What makes up the Nucleus?

• Nuclear pores• Small holes in the nuclear envelope.– Allows RNA and other materials to pass in/out

of membrane

What makes up the Nucleus?

• Nucleolus• Inside the nucleus• Synthesis of Ribosomes• The ribosomes then pass through the

nuclear pores to the cytoplasm.

Organelles

• Mitochondria

• Cellular Respiration takes place in Mitochondria

• Produces useable form of ENERGY for cell.

• Converts organic molecules (carbs) to ATP..

• Have their own DNA (genetic info) and ribosomes

• Double membrane organelle

Organelles

• Endoplasmic Reticulum “ER”• System of membranous tubes and sacs • Acts as a “HIGHWAY”, moving molecules

(proteins) inside cell• Two types: rough and smooth

Rough ER

• With Ribosomes

Smooth ER

• NO ribosomes

Organelles

• Golgi Apparatus• Function: processing, packaging, and sending molecules such as proteins

• Surrounds materials in “vesicle”.

The Golgi body is like ER in that it is system of membranes/sacs. Works closely with Smooth ER and looks similar to it.

Organelles

• Lysosomes• Vesicles produced by Golgi apparatus• Contain digestive enzymes• Get rid of unwanted materials, waste,

damaged cells, etc.

Organelles

• Cytoskeleton• Network of long

protein strands located in the cytoplasm

• Framework…support for cell structure

• Give cell shape.

Parts of Cytoskeleton

• Microfilament• Part of cytoskeleton• Aid cell in movement

Parts of Cytoskeleton

• Microtubule• Part of Cytoskeleton• Hollow tubes made of protein (tubulin)• Maintain cell shape• Act as tracks to guide

Parts of Cytoskeleton

• Intermediate Filaments• Rods that anchor nucleus and other organelles

How does a cell move?

Cilia - hairlike organelles that extend from surface of the cell. There are many of these short hairs on outside. You have cilia in your respiratory tract!!

Flagella - when the hairlike organelles are long and less numerous. Flagella found on sperm cells!

Cilia Flagella

Centrioles

• Help with cell division• Only in animal cells

Choices:

A. Cell membrane

B. Nucleus

C. Rough ER

D. Smooth ER

E. Golgi Apparatus

F. Mito-chondria

G. Ribosomes

Unique Features of Plant Cells

• Cell Wall• Exterior/Outside layer of protection and support for… – Plants– Fungi – Prokaryotes

• Animals do NOT have cell wall!!!!!!!!!!!!• Made of cellulose (complex carbohydrate).

Central Vacuole

• Vacuoles• Storage units– Water, enzymes, wastes, etc.

• They are quite large in plant cell..take up 90% of cell.

• Rarely found in animal cells but very small and few.

• Responsible for turgor pressure in plants

Chloroplasts• Only in the PLANT CELL. • WHERE PHOTOSYNTHESIS

OCCURS• Convert light energy to make

carbohydrates (glucose) for the plant.

• Have their own DNA (genetic info) and ribosomes.

• Double membrane organelle• Contains pigment Chlorophyll.

– Main molecule that absorbs light for cell. (like a solar panel)

Parts of Chloroplasts

Choices:

A. Vacuole

B. Chloroplasts

C. Nucleus

D. ER

E. Cell membrane

F. Cell wall

Comparing Cells

• What do all cells have in common?• Cell membrane• Cytoplasm• Ribosomes• Genetic material

How is prokaryote different from eukaryote?

• Only eukaryotes have membrane bound organelles…especially the nucleus.

• Prokaryotes do have nucleiod.• Eukaryotes are bigger and more advanced.• Prokaryotes were the first cells, bacteria.

How is PLANT cell different from animal cell?

Plant cell summary…

• Usually more square in shape (animal more circular) and more green in color.

• Cell wall, helps make it more rigid.

• Can make its own food (photosynthesis) due to Chloroplasts (plastids).

• Large central vacuole.

This is real picture of what a plant cell looks like.

This is real picture of what an animal cell looks like.

CELL SIZE: Why are cells small?

Volume = How “big”, the amount of space • The number of reactions must increase as the

volume of a cell increases. (The larger the volume the larger the number of reactions needed to support the bigger size)

• Surface Area = The area around the cell, the cell membrane, the amount of area that materials can enter and leave

• All raw materials necessary for a cell’s reactions (metabolism) can enter the cell only through its cell membrane.

• As a cell grows, its SA to V ratio decreases.– Surface Area does not increase as fast as the

Volume• If cell grows too large, the SA (the area of cell

membrane) is not sufficient enough to move enough raw materials to support that volume. At this point the cell cannot get larger.

• What will it do?• Die if it continues to grow larger• Divide • Flatten out (change shape) shape to maximize SA