Chapter 7: Cell Structure & Function
http://koning.ecsu.ctstateu.edu/cell/cell.html
Discovery of Cells
• Robert Hooke (1600’s) discovered “little chambers” (cells) in cork plant
• Anton van Leeuwenhoek (1600’s)used microscope to view living things in pond water. Saw things swimming around!
Discovery of Cells, cont.
• Matthias Schleiden (1838) concluded plants made of cells
• Thoedor Schwann (1839) concluded all animals made of cells
Cell Theory
1. All living things are made up of cells.
2. Cells are the smallest working units of all living things.
3. All cells come from preexisting cells through cell division.
Definition of Cell
A cell is the smallest unit that is capable of performing life
functions.
Examples of Cells
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
Two Types of Cells
•Prokaryotic“pro-” means “before” (like “pre”)“karyon” means “nut” or kernel”No nucleus
•Eukaryotic“eu-” means “true”Has nucleus
Prokaryotic
• Do not have organelles surrounded by membranes
• Few internal structures
• One-celled organisms, Bacteria
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Eukaryotic• Contain organelles surrounded by membranes• Most living organisms
Plant Animal
http://library.thinkquest.org/C004535/eukaryotic_cells.html
“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
http://waynesword.palomar.edu/images/plant3.gif
“Typical” Plant Cell
Eukaryotic Cell PartsOrganelles
Surrounding the Cell
Cell Membrane
• Outer membrane of cell that controls movement in and out of the cell
• Double layers of fat “”phospholipid bilayer”
http://library.thinkquest.org/12413/structures.html
Cell Wall
• Most commonly found in plant cells & bacteria & fungi
• Supports & protects cells
• Made of carbohydrate
http://library.thinkquest.org/12413/structures.html
Inside the Cell
Nucleus
• Directs cell activities
• Separated from cytoplasm by nuclear membrane
• Contains genetic material - DNA
Nuclear Membrane
• Surrounds nucleus• Made of two layers• Openings allow
material to enter and leave nucleus
http://library.thinkquest.org/12413/structures.html
Chromatin
• Form DNA takes most of the time.
• Like spaghetti
• Made of DNA wrapped up w/proteins
Chromosomes
• In nucleus• DNA wrapped up tight
by proteins called “histones”
• Contain instructions for traits & characteristics
http://library.thinkquest.org/12413/structures.html
Nucleolus
• Inside nucleus• Contains RNA to build
proteins
http://library.thinkquest.org/12413/structures.html
Cytoplasm
• Gel-like mixture
• Surrounded by cell membrane
• Contains hereditary material in prokaryotes
Ribosomes
• Each cell contains thousands
• Make proteins• Found on
endoplasmic reticulum & floating in the cytoplasm
http://library.thinkquest.org/12413/structures.html
Endoplasmic Reticulum• Moves materials around
in cell• Smooth type: lacks
ribosomes• Rough type (pictured):
ribosomes embedded in surface
http://library.thinkquest.org/12413/structures.html
Mitochondria
• Produces energy through chemical reactions – breaking down fats & carbohydrates
• Controls level of water and other materials in cell
• Recycles and decomposes proteins, fats, and carbohydrates
http://library.thinkquest.org/12413/structures.html
Golgi Bodies
• Protein 'packaging plant'
• Move materials within the cell
• Move materials out of the cell
http://library.thinkquest.org/12413/structures.html
Lysosome• Digestive 'plant' for
proteins, fats, and carbohydrates
• Transports undigested material to cell membrane for removal
• Cell breaks down if lysosome explodes
http://library.thinkquest.org/12413/structures.html
Vacuoles
• Membrane-bound sacs for storage, digestion, and waste removal
• Contains water solution
• Help plants maintain shape
http://library.thinkquest.org/12413/structures.html
Chloroplast
• Usually found in plant cells (not in animal)
• Contains green chlorophyll
• Where photosynthesis takes place
http://library.thinkquest.org/12413/structures.html
Centrioles
• Used during animal cell division (not present in plant & most other cells)
Prokaryotic Cells
• Ribosomes
• DNA or RNA
• cytoplasm
Cell Boundaries
• Cell Membrane1. Controls what
goes in & out
2. Support & protection
• Cell Wall1. Support &
protection
Diffusion through Cell Boundaries
• Every cell lives in a liquid environment
• Membrane controls movement of dissolved molecules back & forth (in & out of cell)
• (Remember a solution contains a– Solvent: the
substance that dissolves the other stuff (often water)
– solute: the substance that gets dissolved (salt, sugar, ions, etc.)
Concentration of Solutions
• The greater the ratio of solute to solvent, the higher the concentration.
• Ex:
• Solution #1: dissolve 5 g of salt in 1L of water. Concentration= 5g/L
• Solution #2: dissolve 10 g of salt in 1L of water. Concentration=10g/L
Diffusion• In solution, particles move constantly,
colliding & spreading out.• Diffusion is the movement of particles
from area of greater to lesser concentration (b/c of random motion.)
• Requires no energy to move substances across a membrane (b/c moved by random motion)
Equilibrium
• When solute concentration is equal throughout the solution
Osmosis
• The diffusion of water through a membrane
• Some molecules are too large to move through a membrane
How Osmosis Workssee Fig 7-15 on p 185
• If there is a selectively permeable membrane separating 2 solutions w/differing concentrations of solute,
• Water will move from the side where it is in greater concentration to where it is in lesser concentration. (R to L in picture)
Concentration of Solutions
• Isotonic: when the concentration of particles is the same on both sides of membrane
• Hypertonic: “above strength”- the stronger of the 2 solutions (L side)
• Hypotonic: “below strength”- the less concentrated of the 2 solutions (R side)
How Osmosis Works in Cellssee p 186 of text, Fig 7-16
• Isotonic: Cell maintains its shape
• Hypertonic