The Cell Theory

1. All living things are composed of cells

2. Cells are the building blocks of more complex structures

3. All cells come from preexisting cells

Two Classes of CellsProkaryotic

– Lack a true nucleus

– Lack most organelles

– Bacteria

Eukaryotic – Have a true

nucleus– Contain

organelles• Specialized

structures within cells that perform tasks

– Animals– Plants– Fungi – Protists

Microscope Review Question• On high power you

use the large knob to bring a cell into focus. But, all of a sudden the cell is gone!

• Why? What should you do?

• Ooops! Only use the small (fine focus) knob on high power.

• Go back to low power and start over

Microscope Review Question

• A microscope at another school has an eyepiece that provides 5x magnification. The medium power lens provides 10x magnification.

• What is the total magnification on medium power?

• Medium power = 5 x 10• Medium power = 50• Objects will seems 50

times bigger on medium power than they are in real life

Microscope Review Question

• Why couldn’t you focus on three overlapping threads at once?

• They were too thick.• Our microscopes

have a shallow “depth of field” – you only see a tiny “slice” of space at any time

Nucleus- contains genetic information (DNA),

• “brain of the cell”

•Protected by nuclear membrane

•Filled with nucleoplasm

•Nucleolus at the center

Endoplasmic Reticulum- ships products throughout the cell

Rough ER- ships proteins

Smooth ER- ships Lipids

Flagellum- propels cell

Lysosome- digests materials

Centriole- aids in cell division

Cytoskeleton- provides structure and aids in movement

Mitochondrion- converts energy, makes ATP for the cell

Cell membrane- encloses and controls what enters and leaves the cell

Golgi apparatus-ships products outside of the cell

Ribosomes-make proteins

Central vacuole- stores water

Cell wall- provides structure

Chloroplast- Site of photosynthesis

Plant vs. Animal Cells

Plant cells

• have cell walls

• contain chloroplasts

•look green

• have larger vacuoles

Cell Membrane

“Water loving” (Hydrophilic) heads face the inside (cytoplasm) and outside of the cell where there is lots of water

“Water fearing” (Hydrophobic) tails face each other

http://www.pearsonsuccessnet.com

Online 6.4 pg 2 internal membrane system

Selectively Permeable Membrane• Small and uncharged

substances move freely across the cell membrane – No attraction to charged

heads

• Charged substances need help getting across – Attracted to charged heads

• Large substances cannot cross

Diffusion• Movement of

molecules from an area of high to low concentration until a balance is reached

• No energy needed

• Small, uncharged substances– O2 and CO2

• When balanced, molecules still move, but at the same rate in both directions

Cells are limited in size• Food, nutrients, and

gases must enter and leave through the membrane

• The larger the cell, the larger the surface area needs to be to stay efficient

• Cells with a high surface area: volume ratio are most efficient

• Conclusion- in order to be efficient, cells must be small!

http://www.pearsonsuccessnet.com

Lab 6 pg2

Osmosis Diffusion of water across a selectively permeable membrane

Cells react to the solutions they are in:– Hypotonic- lower

concentration of solute than water- cells swell (cytolysis)

– Isotonic- equal concentrations of solute and water- cells don’t change

– Hypertonic- higher concentration of solute than water- cells shrink (plasmolysis)

Exocytosis• Releasing

large products from a cell

http://www.coolschool.ca/lor/BI12/unit4/U04L05.htmhttp://www.middlesexcc.edu/faculty/Barbara_Bogner/111unitone.html

Endocytosis• Engulfing

large products into a cell

“Diffusion Across a Model Cell Membrane” Lab Activity

Glucose / Starch Solution

Water and Iodine

Pre-Lab Discussion

How will you determine if starch diffused?In what direction will it move?

How will you determine if glucose diffused?In what direction will it move?

How will you determine if iodine diffused?In what direction will it move?

How will you determine if water diffused?In what direction will it move?