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