Chapter 7 CellsChapter 7 Cells

K – W – L Know-Want to know - Learned

Cells Warm Up JournalK – W – L

Know-Want to know - LearnedJournal: What do you know about Cells…

Journal: What do you want toknow about Cells…

What is a cell?What is a cell?

• A cell is the A cell is the smallestsmallest unit of unit of lifelife that that can carry on all the can carry on all the functionsfunctions of life. of life.

Who first discovered cells?

• An English scientist looked at cork with an early light microscope; they reminded him of the rooms or “cells” where monks lived.

• Robert Hooke

Who first observed living cells?

• Anton van Leeuwenhoek in 1673

• He viewed pond water organisms and called them “animalcules” or “Wee beasties”. – We now call them protists.

What are the three parts of What are the three parts of the cell theory?the cell theory?

1. 1. All living things are made of one or more All living things are made of one or more cellscells

2. Cells are the basic units of2. Cells are the basic units ofstructurestructure & & functionfunction in all organisms. in all organisms.

3. Cells come only from the3. Cells come only from thereproductionreproduction of existing cells. of existing cells.

With better microscopes, scientist observed structures

inside of cells….

• Organelles- small structures with in the cell that perform specific functions.

• Cells can be divided into two groups, those that contain membrane bound organelles and those that do NOT!!!!

What are the two types of cells?

Eukaryote - cells that have a nucleus and membrane-bound organelles.

Examples: plant and animal cells

Prokaryote cells that do not have a nucleus and membrane-bound organelles.

Examples: bacteria

Cells

Mind Map

Prokaryotic Eukaryotic

2 types

Do Not have membrane bound organelles

Have membrane bound organelles

Animal Plant

Journal:

• How are eukaryotes different from prokaryotes? (Use a complete sentence)

Eukaryotes are different from prokaryotes because eukaryotes -------- and prokaryotes -------.

• What are the 3 parts of cell theory?

• Inside a living cell there is constant activity.

• A cell has many parts that work together to accomplish the functions of life. – In eukaryotic cells, many of these molecules

are organized in tiny organelles that perform specialized functions inside the cell.

Cell Structure and Function

The 3 main parts of the cell?

1. Cell Membrane (Plasma Membrane) -controls which substances pass in and out of the cell.

2. Nucleus- contains the hereditary information and directs most of the cell’s activities.

3. Cytoplasm- the region between the cell’s nucleus and the cell membrane, which contains the organelles and the cytosol (jelly-like substance)

Journal

In your own words, describe the “job” for each of the 3 main parts of the cell

• Cell membrane:

• Nucleus:

• Cytoplasm:

What is the cell membrane’s structure and function?

• Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells.

Journal Review

• What is homeostasis???

Selectively permeable

• Allows some molecules to pass while others are kept out

• Why might this be important????

Structure of the plasma membrane

Phospholipid bi-layer– Polar head (hydrophillic - water loving)– Non-polar tail (hydrophobic- water fearing)

Structure of the plasma membrane

Phospholipid bi-layer– Polar head (hydrophillic - water loving)– Non-polar tail (hydrophobic- water fearing)

The two layers are arranged

so that polar heads face

outside (water) and the tails

are on the interior.

• Within the phospholipid bi-layer there are proteins and cholesterol– Proteins

• Channels for transport• Signal receptors (receive messages from outside of

the cell)– Cholesterol

• Stabilizes the plasma membrane

Surface Area to Volume Ratio

• The rate of diffusion into and out of a cell is proportional to the surface area of the plasma membrane.

• Diffusion can only supply adequate amounts of nutrients if the surface-area-to-volume ratio is large enough.

• As cell size increases, the rate of diffusion from the plasma membrane to the center decreases and the surface-area-to-volume ratio decreases. This is a very important reason why most cells are tiny.

Now Onto Organelles