Cells

Objective: To learn the structure and function of typical human cells

There are many types of cells

About Cells

• The cell is the basic unit of structure and function in living things

• Living things contain one or more cells– Protozoans contain a single cell– Humans contain thousands of billions of cells

• Cells are usually microscopic, but range from the size of a bacteria to the size of an unfertilized ostrich egg.

A bacterial cell is way too small to see. It’s even hard to see with a microscope. Click the picture below to see an enlarged view

• Living things contain one or more cells– Protozoans contain a single cell– Humans contain trillions of cells

Protozoan, one cell Human being, 50 000 000 000 000 cells

• But each human being started as one cell!

Fertilized human egg cell(ovum)

Three Main Parts of a Cell

• A cell usually has three distinct areas or layers:– The membrane (lipid bilayer & proteins)– The cytoplasm (cytosol & organelles)– The nucleus (DNA) 1. Membrane

2.Cytotoplasm

3. Nucleus

Some Cell Videos

• Cell biology

• David Bolinski Animates a cell

• The finished product: Link not working

• Another Cell video: Cell Journey

• A thyroid cell

The Cell Part 1: The Cell Membrane

• All cells have a cell membrane (AKA: plasma membrane). – Plant, algae, fungi and bacteria cells have an additional

outer layer called the cell wall• Don’t confuse the cell wall with the cell membrane.• Animal and protozoa do not have a cell wall, just a membrane! • Cells that have a wall also have a membrane inside the wall!

• The membrane is an elastic envelope surrounding the cell– It is composed of lipids and protein.– It is semi-porous (semi-permeable)– It controls the passage of materials in and out of the cell.

Structures connected with the membrane

• The membrane may have some of the following:– Microvilli: non-moving hair-like projections

which increase surface area for absorbtion– Cilia: moving hair-like projections used for

locomotion– Flagella (sing. Flagellum): larger, whip-like

projection used for locomotion.– Pinocytes: indentations in the membrane

where materials are brought into the cell.

The Lipid Bilayer

2 fatty acids

phosphate

• Most of the cell membrane is made up of a double layer of phospholipid molecules, also called a lipid bilayer. The “head” (or phosphate) end of each lipid molecule is hydrophilic, the “tail” (or fatty acid) end is hydrophobic

The Membrane Proteins• The cell membrane also contains many protein

molecules. Some sit on the surface of the membrane (peripheral proteins) and others are embedded in it (integral proteins). A few pass right through the membrane from inside to outside (trans membrane proteins)

A drawing of the membrane

Copy the “simplified diagram” from the blackboard

Part 2: The Cytoplasm• The cytoplasm consists of a) cytosol and

b) organelles.– The cytosol is the liquid portion of the cell.

• It is a complex mixture of materials: water, gases, wastes, nutrients, raw materials

– The Organelles• Suspended in the cytoplasm are many tiny structures

called organelles

• An older name for cytoplasm was protoplasm• This word is used less frequently now, since has come

to imply a living material, rather than cell contents.

The Organelles

• Mitochondria (sing. mitochondrion).

• Endoplasmic reticulum– Rough– Smooth

• Ribosomes

• Golgi Apparatus

• Lysosomes

• Vacuoles

Mitochondria

• The mitochondrion is the powerhouse of the cell. Here chemical energy is released by the break down of food particles.

• It is a bean-shaped organelle with an internal membrane folded into many “cristae” .

Endoplasmic Reticulum

• The “ER” or Endoplasmic Reticulum is a network of tubes and membranes that runs through the cell. Its purpose is to transport materials quickly through the cell

• Rough ER– Has ribosomes

• Smooth ER– Has no ribosomes

Ribosomes

• Very tiny, round organelles associated with protein synthesis

• They help manufacture the cell’s proteins.

Golgi Apparatus

• A network of membranes, similar in appearance to the ER

• Its purpose is to modify and “package” proteins that will be secreted.

Lysosomes & Vacuoles

• These are storage areas within a cell

• Lysosomes hold digestive enzymes that help the cell metabolize food. When a cell dies, the digestive enzymes help dissolve the dead cell

• Vacuoles store food or water

Part 3: The Nucleus

• The nucleus consists of:– The nuclear membrane or envelope (with tiny

pores in it)– The nucleoplasm– The chromatin material

• (chromosomes)

– The nucleolus

Typical Human Cell

Types of Cells

• Prokaryotic Cells: A simpler type of Cell found in Bacteria and Cyanobacteria (Blue-green algae)– Prokaryotic cells have no nucleus, the DNA or RNa

floats freely in the cell. – Prokaryotic cells have no membrane bound organelles

(ie. No mitochondria, no endoplasmic reticulum, golgi apparatus, nor any organelle made of membranes)

• Eukaryotic Cells: Typical cells with a nucleus and many types of organelles– There are 3 main types of Eukaryotic cells:

• Animal Cells: no cell wall, small vacuoles• Plant Cells: cell wall, large central vacuole• Protist cells: between plant and animal cells, often with pellicle• Fungal cell: similar to plant cells but with no chlorophyll

Prokaryotic

Eukaryotic

Exercise

• Label the cell diagram

• p90 #6-22

A. Cell Membrane

B. Smooth ER

C. Cytoplasm

D. Mitochondrion

E. Ribosome

F. Nucleus

G. Golgi apparatus

H. Lysosome

I. Endocytosis / Exocytosis

J. Nucleoplasm or “matrix” (containing chromatin)

K. Nucleolus

L. Nuclear membrane “envelope” (with nuclear pores in it)

M. Rough ER

Slide Show(some neat cell images)

A few of the many shapes of cells found in humans

Human Blood Cells(as they appear under typical microscope)

Unstained red blood cells stained red and white blood cells

Nerve Cell

Nerve Cell

Muscle Cells

About a thousand plant cells in a small piece of leaf

Plant Cells (high contrast B&W)

Protozan cells

Next Page: Answers

Answers Page 90

• 6.b, 7. a, 8.a, 9. c• 10. b 11. c 12. d 13. c• 14. a 15. b• 16 (corrected when handed in)• 17. The organelle is a mitochondrion, the structures are

called cristae, which provide space for chemical reactions to occur.

18. The ratio of surface area to volume limits cell size19. (correct when handed in)20. The membrane is selectively permeable because it

allows some materials to cross easily but blocks others.21, 22 (correct when handed in)