The Cell Theory

1. How are cells like bricks in a wall?

Cells are the individual units used to build living things just like bricks are the individual units used to build the wall.

2. How are cells different from bricks in a wall? “Cells are alive. Bricks are not alive.”

3. Draw pictures of the following cells to illustrate different cell shapes:

Red Blood Cell

Skin cell

Bone cells

Nerve Cell

SPERM

Why do these cells have such different shapes? “The different shapes helps the cell do its job more efficiently.”

How do these cells get such different shapes? “The cell is following a genetic design to construct the plasma membrane a certain way.”

4. Robert Hooke: Year of his cellular discovery: 1665

What was he observing? A THIN slice of cork from under the bark of a tree.

What was he observing with? A very weak, homemade microscope

What did he discover? He was the first to observe cells. He was actually looking at the cell walls.

Why did he name his discovery : “CELLS”? The cell looked like the tiny rooms that the priest slept in at the monastery…which were called cells.

5.How long did it take the Cell theory to be developed? 200 years Was it the result of just one scientist work? NO

6. Matthias Schleiden: Who was he? A German Botanist. What year did he make his cellular discovery: 1838

Schleiden Discovered that ALL parts of the Plant were made Of cells..Not just Cork!

7. THEODOR SCHWANN Who was he? A German Zoologist Year of his discovery? 1839

Schwann German zoologist Discovered that All parts of an Animal were made up of cells.

8. Rudolf Virchow: Who was he? A Russian Biologist What did he discover?

VIRCHOW Russian scientist that first observed mitosis. Learned that cells come from other cells.

9. State the three points of the cell theory:

All living things are made of cells. The cell is the basic unit of life! Cells come from other cells!

10. Why is the Cell theory considered to be the Cornerstone of Biology? “The cell theory applies to ALL LIVING THINGS!”

11. What type of environment are cells found in? “All cells are surrounded by a nutrient rich fluid.”

Fluid environment

12. Why are human cells surrounded by blood and tissue fluids?

Cells must obtain materials from the fluid environment and release waste materials back into the fluid environment.

What is the name of this fluid that surrounds the cells? “Interstitial fluid”

13. What keeps the cytoplasm from mixing with the interstitial fluids? “A semi-permeable plasma membrane called the CELL MEMBRANE.”

14. Why is the plasma membrane (cell membrane) considered the cell “gate keeper”?

The job of the cell membrane is to control what enters and leaves the cell.

15. What is Homeostasis?

A healthy balance of nutrients entering and waste leaving a cell.

16. How does the plasma membrane function in maintaining homeostasis?

It maintains homeostasis by only allowing those things to pass into the cell that the cell needs. If there is no need, the cell membrane will not allow it to pass into the cell.

17. Why is the cell membrane called a “selectively permeable membrane”? “It only allows certain molecules to pass through or permeate the membrane”

18. Are all cell permeable to the same molecules? No! Different cells have different jobs..Thus different nutrient requirements.

19. Why would a particular cell be permeable to a specific molecule yesterday, but impermeable today?

Yesterday it needed that molecule. Today it doesn’t need it.

20.Why do you suppose some molecules will move freely across the membrane while others require active transport?

Tiny molecules like oxygen and carbon dioxide gas can move freely. Fat soluable molecules can move freely. Big molecules like sugar require active transport.

21. How long have scientist been working on a model of the plasma membrane? 50 years

22. Why is it necessary to keep adjusting the model?

As technology improves, such as the invention of the electron microscope, we keep learning new things.

23. Describe the lipid bilayer:

The plasma membrane is composed of TWO LAYERS of molecules called phospholipids.

24. What is the difference between the structure of a lipid and a phospholipid?

A lipid is composed of two strands of fatty acids. The phospholipid has a phosphate head attached to the lipid.

26. Describe a phopholipid:

The phosphate head is Polar! It is hydrophilic – It draws water to it.

The fatty acid tails are non- polar. They are hydrophobic! They push water away.

27. Draw a picture of the plasma membrane showing the arrangement of the phospholipids in the lipid bilayer:

28. Explain the properties that make the cell membrane act like a very fine film of oil:

Within each layer, the fatty acid tails can wag back and forth, and entire phospholipids can glide sideways through their layers.

29. Explain the job of the cholesterol molecules found in the plasma membrane:

JOB #1 The cholesterol molecules bind the two layers of the lipid bilayer together.

JOB #2 It makes the lipid bilayer strong, yet flexible.

30. Describe the two ways proteins are found in the plasma membrane:

Some proteins are embedded in the bilayer providing passageways through the cell membrane. Others lie on top and act as recognition markers

31. Why is the model of the plasma membrane called the Fluid Mosaic Model?

It is called the fluid mosaic model because the phospholipids and plasma proteins are constantly moving like a fluid, and the membrane has a pattern of proteins embedded in it.

32. What is the job of the phospholipid bilayer? “To provide structure, determine shape, and forms most of the cell’s outer boundary.”

33. List the four functional roles of the plasma proteins:

Role #1:.Control which particles can cross the membrane.

Role #1:.Serve as enzymes and take part in chemical reactions.

Role #1:.Act as recognition markers

Role #1:.Help fight disease by sending a chemical message to the next cell, warning it of viruses in the area. Causes the neighboring cells to secrete INTERFERON to block the virus from attacking it.

34. Could different cells in your body perform different functions if their membranes were all permeable to exactly the same materials? Explain.

No. Some cells, like bone, need calcium. Nerve cells need copper. Different cells have different needs.