Introduction to the Cell

Essential Questions

1) Identify the characteristics that are similar in all cells.

2) Compare and contrast eukaryotes and prokaryotes.

Cell Theory

• All living things are made of cells

• Cells are the basic unit of structure & function in organisms

• Cells only come from other cells (reproduction)

Cell Diversity

• Cell come is a variety of sizes– Most are too small to see

without a microscope

• A cell’s size is limited by the ratio of its surface area to its volume– Cells take in food through

their surface– If they become too big,

there is not enough surface area for them to get enough food!

Internal Organization

• Cells contain organelles (internal structures that perform specific functions for the cell)

Prokaryotes vs. Eukaryotes (Analogy)

Prokaryote Cell

• No organelles

• No Nucleus (still has DNA)

• Very Small

• Only single celled organisms.

• Bacteria are prokaryotes!!!

Eukaryote Cells

• Have organelles

• Have a nucleus

• Very large

• Can form multicellular organisms.

• Plants, Animals, Fungi and Protists

Prokaryotic Cell vs. Eukaryotic Cell

Parts of the eukaryotic Cell – cell membrane

Essential Questions:

1. Identify the macromolecules that make up the cell membrane.

2. Describe how the cell membrane is selectively permeable.

Three Main Components of Eukaryotic Cells

1. Cell membrane

2. Nucleus

3. Cytoplasm (includes all of the other organelles)

Cell Membrane

Function of the Cell Membrane =Regulates what enters and exits the cell

Selectively Permeable

• The cell membrane will only allow some things to enter or exit!!!

You - Stay OUT!!!!!

You can come IN!!!!!

Phospholipid Bi-layer = 2 rows of lipids that form most of the cell membrane.

• Hydrophilic – loves water (Head portion)

• Hydrophobic – hates water (tails portion)

– Tails are made of two fatty acids

• Why do you think the cell membrane has to be 2 layers, as shown in picture b?

Polar vs. Non-Polar• Polar = charged particles.

Example: water

Non-polar = not charged particles.

Example: lipids

Opposites do not attract in the world of polar & non-polar.

Phospholipids have a polar head and non-polar tails.

Membrane Proteins

• Integral Proteins

– In the cell membrane

• Peripheral Proteins

– On the cell membrane

• Three types of these proteins

– 1. Channel Proteins

– 2. Receptor Proteins

– 3. Marker Proteins

Fluid-Mosaic Model = description of the cell membrane structure.

• “Fluid” = cell membrane is in constant movement.

• “Mosaic” = it is a combination of Lipids, Proteins and Carbohydrates all functioning together!!

END OF NOTES

Plants vs. Animals

Plant Cells – have 3 organelles that are not found in animal cells.

• Plants have:

- Chloroplasts

- Cell Walls

- a large central Vacuole.

• Plant Cells are Eukaryotes!!!!

Animal Cells – have 1 organelle that are not found in plant cells.

• Animals have:

– Centrioles

• Animals are Eukaryotes!

Viruses – Are they living?

• A virus is basically DNA surrounded by a protein coat/shell.

• They do not have any other organelles or a cell membrane.

• Are only “alive” when they invade another cell!!!

Identify These Cell Types.