Chapter 7 Cells

7.1 Life is Cellular, Pgs. 190-195

7.2 Cell Structure, Pgs. 196-207

7.3 Cell Transport, Pgs. 208-213

7.4 Homeostasis and Cells, Pgs. 214-217

Chapter Vocabulary

7.1 CellCell TheoryCell MembraneNucleusEukaryoteProkaryoteCytoplasmOrganelleVacuole

7.2LysosomeCytoskeletonCentrioleRibosomeEndoplasmic reticulumGolgi apparatusChloroplastMitochondrionCell WallLipid BilayerSelectively permeable

7.3DiffusionFacilitated diffusionAquaporinOsmosisIsotonicHypotonicHypertonicOsmotic pressure

7.4HomeostasisTissueOrganOrgan systemreceptor

7.1 Life is Cellular, Pgs. 190-195

• light microscopes can produce clear images of objects only to a magnification of about 1000 times.

• Most living cells are nearly transparent, making it difficult to see the structures within them.

• Using chemical stains or dyes can usually solve this problem. Some of these stains are so specific that they reveal only compounds or structures within the cell.

f microscope

Compound Light Microscopes and Cell Stains

Onion skin cells

Light Microscopes and Cell Stains

Human Cheek Cells

**Can you see the nucleus inside?

http://www.youtube.com/watch?v=7pR7TNzJ_pA&feature=related

You can also hook the microscope up to a video camera and either a computer or tv. See the link below for a video taken of a light microscope slide containing an amoeba (a single-celled organism).

Electron Microscopes (SEM) • In scanning electron microscopes, a pencil-

like beam of electrons is scanned over the surface of a specimen.

• Because the image is of the surface, specimens viewed under a scanning electron microscope do not have to be cut into thin slices to be seen.

• Scanning electron microscopes produce three-dimensional images of the specimen’s surface.

MicrobeCholera Bacteria

Electron Microscopes (TEM) • Transmission electron microscopes make it possible to explore cell

structures and large protein molecules.

Because beams of electrons can only pass through thin samples, cells and tissues must be cut first into ultra thin slices before they can be examined under a transmission electron microscope. Thus, electron microscopy can be used to examine only nonliving cells and tissues.

• Transmission electron microscopes produce flat, two-dimensional images.

Mitochondrion from human lung

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)

Cork cells underThe microscope

Robert Hooke Anton van Leeuwenhoek

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

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

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

Cell Features

ALL cell 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

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

• Typical bacteria structure

• Notice that there is nucleus inside.

Eukaryotic Cells

• Cells found in plants, animals, protists, and fungi

 • 4 main parts:

1.Cell membrane2.Cytoplasm3.Nucleus4.Organelles

• Usually found at center of cell• Has a nuclear membrane &

nuclear pores•  Contains cell’s DNA in one of 2

formso chromatin - DNA bound to

protein (non-dividing cell)o chromosomes - condensed

structures seen in dividing cell•  Also contains an organelle

called nucleolus - which makes the cell’s ribosomes

Section 7.2: Cell Structure, Pages 196-207

Nucleus

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

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

*A vesicle forms with Golgi to transport substances outside cell.  

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

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

Cytoskeleton – Helps cell maintain support & shape; movement

a. microtubules-hollow structures; also help build cilia  flagella

b.  microfilaments-threadlike

c.  centrioloes-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

THE ANIMAL CELL

THE PLANT CELL

Plant Cell Parts

Plants 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

CELL MEMBRANE• It is composed of a double layer of phospholipids with

proteins embedded throughout

http://www.youtube.com/watch?v=moPJkCbKjBs&feature=related

A phospholipid

An animal cellCell Membrane Composition

4

32

1

• The cell membrane is selectively permeable. In fact, this is one of the most important properties of the membrane.

• What do you think selective permeability means? Maybe this picture will help.

Selective Permeability

Plasma membrane of budding yeast stained with green fluorescent dye

If you are still stuck, maybe this will helpThese objects are selectively permeable.

7.3 Cell Transport, Pgs. 208-213

Diffussion

This is a type of passive transport because it does not use the cell’s energy (ATP).

• The process by which particles move from an area of high concentration to an area of lower concentration is known as diffusion. http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif

• Diffusion is the driving force behind the movement of many substances across the cell membrane.

http://www.youtube.com/watch?v=H7QsDs8ZRMI

Diffusion

Diffusion depends upon random particle movements.

http://www.youtube.com/watch?v=AYNwynwaALo&feature=related http://www.youtube.com/watch?v=s0p1ztrbXPY&feature=related

Facilitated Diffusion- An example is Osmosis No Energy Required!!!!

• Molecules that cannot directly diffuse across the membrane pass through special protein channels in a process known as facilitated diffusion.

• The movement of molecules by facilitated diffusion does not require any additional use of the cell’s energy.

Can you see the channels in the membrane?

Osmosis: An Example of Facilitated Diffusion

• Many cells contain water channel proteins, known as aquaporins, that allow water to pass right through them. Without aquaporins, water would diffuse in and out of cells very slowly.

*** Osmosis is the diffusion of water through a selectively permeable membrane.

Osmotic Pressure

• For organisms to survive, they must have a way to balance the intake and loss of water.

• The net movement of water out of or into a cell exerts a force known as osmotic pressure.

http://www.youtube.com/watch?v=0c8acUE9Itw&feature=related

http://www.youtube.com/watch?v=aeL6VL4cAmE&feature=related

Osmositic pressure causes water to move into or out of an egg

Osmotic Pressure• Cells placed in an isotonic solution have the same concentration of

solution inside and outside of the cell. The shape of the cell does not change when placed in isotonic solution.

• In a hypertonic solution, water rushes out of the cell, causing animal cells to shrink and plant cell vacuoles to collapse.

• In a hypotonic solution, water rushes into the cell, causing cells to swell.

Red Bood Cells in 3 Types of Media/SolutionsCan you tell which solution is which?

Active Transport- Requires Energy• Cells sometimes must move materials against a concentration

difference.

• The movement of material against a concentration difference is

known as active transport. Active transport requires energy. http://www.youtube.com/watch?v=STzOiRqzzL4&NR=1

Active Transport of Large Molecules

• Larger molecules and clumps of material can also be actively transported across the cell membrane by processes known as endocytosis and exocytosis.

http://www.youtube.com/watch?v=kfy92hdaAH0&feature=channel

http://www.youtube.com/watch?v=4gLtk8Yc1Zc&feature=related

7.4 Homeostasis and Cells Pages 214-217

• A single-celled, or unicellular, organism does everything you would expect a living thing to do.

http://101science.com/paramecium.htm

• Just like other living things, unicellular organisms must achieve homeostasis, relatively constant internal physical and chemical conditions.

• To maintain homeostasis, unicellular organisms grow, respond to the environment, transform energy, and reproduce.

The Cell as an Organism

Cell Specialization • The cells of multicellular organisms are specialized, with different cell

types playing different roles.

• Some cells are specialized to move, others to react to the environment, and still others to produce substances that the organism needs.

• No matter what the role, each specialized cell contributes to the overall homeostasis of the organism.

http://www.youtube.com/watch?v=9duvzqvVflw

• This bacteria is has specialized cilia to help it move.

• What type of microscope was used here? How do you know?

Cellular Communication • Cells in a large organism communicate by means of chemical

signals that are passed from one cell to another.

• These cellular signals can speed up or slow down the activities of the cells that receive them,

http://www.youtube.com/watch?v=ONljvPh1ykY&feature=related

• These cells are called neurons. They reach out and connect to other neurons so they can communicate with each other.