• The Cell Theory grew out of the work of many scientists and improvements in the microscope.Scientists that contributed to the Cell Theory: Hooke: Leeuwenhoek: Schleiden: Schwann: Virchow:

• Early studies led to the development of the cell theory.The Cell theory has three principles.

1. All organisms are made up of cells2. All existing cells are produced by other living cells3. The cell is the most basic unit of lif e

There are two cell types: Prokaryotic cells and Eukaryotic cells.

All cells share certain characteristics.

1. All cells are enclosed by a membrane

2. All cells are fi lled with cytoplasm; a jellylike substance that holds things

Bacterium(colored SEM; magnification 8800x)

cell membrane

cytoplasm

Characteristics:1. Prokaryotic Cells do not

have a nucleus2. Prokaryotic Cells do

not have membrane-bound organelles.

Bacterium(colored SEM; magnification 8800x)

cell membrane

cytoplasm

Prokaryotic Cells: Pro = No

Eukaryotic Cells: Eu = YouCharacteristics:• Do have a nucleus and• Do have membrane- bound organelles

nucleus

cell membrane

organelles

cytoplasm

Cells Have an I nternal Structure• Cytoskeleton has many

functions1. Microtubules give cells

shape; move DNA2. I ntermediate fi laments,

give cells strength3. Microfi laments allow

cells to move and divide4. Cytoplasm important f or

cell structure5. Water allows chemical

reactions to occur

NucleusStores genetic information

• Nuclear envelope – double membrane that encloses DNA

• Nuclear Pores –

• Nucleolus – contains tiny organelles f or making proteins

Endoplasmic Reticulum Series of f olded membranes

“I ntracellular Highway” Many processes occur on surface and lumen

(interior of membranes)ex: Production of proteins and lipids

Endoplasmic Reticulum• There are two types:

– Rough Endoplasmic Reticulum (R.E.R.): contain ribosomes

– Smooth Endoplasmic Reticulum (S.E.R.): no ribosomes

Lumen

Ribosome's link amino acids to f orm proteins

Made of protein and RNA

Made in nucleolus; leave through nuclear pores

Ribosome

Golgi Apparatus

• Closely stacked membranes• Package, Sort, and Processes

Proteins f rom the E.R.

Vesicles• Membrane-bound sacs pinch off f rom

E.R. and fuse with Golgi Body; transport materials

Mitochondria• Supply energy to the cell• Consists of two membranes; inner

membrane has lots of folds, Why?• Have their own DNA and ribosomes

• Fluid-fi lled sacs used f or storage• Central vacuole unique to plant cells

– plants shrivel when central vacuoles don’t have enough water

– Can contain toxins that help the plant survive

Vacuoles

• Contain enzymes inside to digest material; defend cell f rom invading bacteria and viruses

• Surrounded by a membrane; protects cell f rom being broken down

Lysosomes

Centrosome and Centrioles• Centrioles are tubes found

in the centrosomes– Centrioles help divide

DNA.• Centrosomes make

microtubles which make spindle fi bers

– Centrioles form cilia and flagella

Plant cellsHave TWO features Animal Cells Do Not

Cell wall: gives protection, support, and shape to cell

Chloroplasts: organelles that perform photosynthesis

Cell City AnalogyIn a far away city called Grant City, the main export and production product is the

steel widget. Everyone in the town has something to do with steel widget making and the entire town is designed to build and export widgets. The town hall has the instructions for widget making, widgets come in all shapes and sizes and any citizen of Grant can get the instructions and begin making their own widgets. Widgets are generally produced in small shops around the city, these small shops can be built by the carpenter's union (whose headquarters are in town hall).

After the widget is constructed, they are placed on special carts which can deliver the widget anywhere in the city. In order for a widget to be exported, the carts take the widget to the postal office, where the widgets are packaged and labeled for export. Sometimes widgets don't turn out right, and the "rejects" are sent to the scrap yard where they are broken down for parts or destroyed altogether. The town powers the widget shops and carts from a hydraulic dam that is in the city. The entire city is enclosed by a large wooden fence, only the postal trucks (and citizens with proper passports) are allowed outside the city.

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment. Acts like a fence.

Cell membranes are composed of two phospholipid layers

• Phospholipids have 3 parts:– Charged phosphate group– Glycerol– Two fatty acid chains

• Label the head• Label the tail• Which part is attracted to water?

• Cell membranes are composed of two phospholipid layers.– The cell membrane has two major functions.

• boundary• controls passage

cell membrane outside cell

inside cell

cell membrane

• Cell membranes are composed of two phospholipid layers.– The cell membrane is made of a phospholipid bilayer.– There are other molecules embedded in the membrane.

protein

cholesterol

proteincarbohydratechain

protein channel

Functions

Cholesterol:

Proteins:

Carbohydrates:

Cell membranes are composed of two phospholipid layers.

– The fluid mosaic model describes the membrane.

• Fluid: Cell membrane moves, not rigid– Does not flip, though, outside stays out, inside stays in

• Mosaic: variety of molecules similar to tiles with different textures and patterns

• Cell membranes are composed of two phospholipid layers.– The cell membrane is selectively permeable.

What does selective mean?

What does permeable mean?

So, what does selectively permeable mean?

• Chemical signals are transmitted across the cell membrane.– Receptors bind with ligands and change shape.– There are two types of receptors.

• intracellular receptor

Examples: Aldosterone in kidneys

• Chemical signals are transmitted across the cell membrane.– Receptors bind with ligands and change shape.– There are two types of receptors.

• intracellular receptor• membrane receptor

Examples: red blood cells carrying carbon dioxide

KEY CONCEPT Materials move across membranes because of concentration differences.

3.4 Diffusion and Osmosis

Passive transport does not require energy input from a cell.

• Molecules can move across the cell membrane through passive transport.

• There are two types of passive transport.

• osmosis

• diffusion

3.4 Diffusion and Osmosis

Diffusion and osmosis are types of passive transport.

• Molecules diffuse down a concentration gradient.

3.4 Diffusion and Osmosis

Where will the ball roll?

Does it take energy?

Diffusion and osmosis are types of passive transport.

• Osmosis is the diffusion of water molecules across a semipermeable membrane.

3.4 Diffusion and Osmosis

Which direction will the water molecules move?

• There are three types of solutions. • Isotonic: Iso means equal so…

3.4 Diffusion and Osmosis

• Hypotonic: Hypo = below so…

• Hypertonic: Hyper = above so…

Some molecules can only diffuse through transport proteins.

• Some molecules cannot easily diffuse across the cell membrane.

• Facilitated diffusion is diffusion through transport proteins.

• Move with concentration gradient!

• No energy required

3.4 Diffusion and Osmosis

KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.

3.5 Active Transport, Endocytosis, and Exocytosis

What is different from this picture than the picture in the previous slides?

Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient.

• Active transport is powered by chemical energy (ATP).

3.5 Active Transport, Endocytosis, and Exocytosis

• Cells use active transport to maintain homeostasis.

• Active transport occurs through transport protein pumps.

A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis.• Cells use energy to transport material in vesicles.

• Endocytosis is the process of taking material into the cell.

3.5 Active Transport, Endocytosis, and Exocytosis

• Phagocytosis is a type of endocytosis; engulfs Large particles Vesicle

• Exocytosis is the process of expelling material from the cell.

3.5 Active Transport, Endocytosis, and Exocytosis

Vesicle