Chapter 7

Cellular Structure and Function

Chapter 7.3

Cell Structures and Organelles

Cell OrganellesCell Part Function

Cytoplasm Semfluid material that surrounds the organelles and provides a place for chemical reactions to take place.

Cytoskeleton A network of long, thin protein fibers that form a framework and support system for the cell; anchors all the organelles

Nucleus Control center of the cell; contains the cell’s DNA; surrounded by nuclear membrane (envelope)

Ribosomes Produces proteins

Nucleolus Produces ribosomes

Endoplasmic reticulum Folded membrane system that is the site for protein and lipid production

Smooth ER Area with no ribosomes attached; place where many carbohydrates and lipids are produced

Rough ER Ribosomes are attached and produce proteins

Cell OrganellesCell Part Function

Golgi Apparatus Flattened membranes that modified, sorts, and packages proteins

Vacuoles Temporary storage for the cell; used to store food, enzymes, and other materials needed for the cell

Lysosomes Structure containing enzymes used to digest waste

Centrioles Used in cell reproduction

Mitochondria Produce energy by breaking down sugars

Chloroplasts Capture light energy and convert it to chemical energy (food); found in plant cells

Cell wall Thick, rigid fibers that surround the plasma membrane and protects the cell

Cilia and Flagella Used for cell movement in some eukaryotic cells

Cytoplasm and Cytoskeleton

Nucleus and Nucleolus

Ribosomes

Smooth and Rough Endoplasmic Reticulum

Golgi Apparatus

Vacuole

Animal Cell

Plant Cell

Lysosomes

Centrioles

Mitochondria

Chapter 7.4

Cellular Transport

Predict• Food coloring

demonstration– Drops of red and blue

food coloring are added to opposite ends of a container of water.

• Hypothesize:– What will happen when

the food colorings are added?

– What will happen after 5 minutes?

Observation & Explanation • Observe:– What happened to our food colorings?

• Explain:– How can this result be explained?

Figure 7.20 © Glencoe-McGraw Hill (2007)

Diffusion• Substances dissolved in water (solutes) move

constantly in random motion; this is call Brownian Motion

• Causes diffusion– net movement of particles from an area where

there are many particles of the substance (high concentration) to an area where there are few particles of the substance (low concentration)

• There are two components of solution:– Solvent – a substance in which another substance

is dissolved– Solute – the substance that is dissolved

Diffusion

• Movement of substances from high concentration to low concentration

• Caused by the RANDOM movement of particles• Requires no energy input!

http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif

http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion2.gif

• Interactive Diffusion Activity:http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP1903

Dynamic Equilibrium

• Once a uniform purple color is reached, the food coloring particles continue to move randomly.

• However, at some point, all particles of a substance (in this case food coloring) will be as spread out as they can and there will no longer be areas of high and low concentration.

• When this occurs, dynamic equilibrium has been reached.

Diffusion in Cells

• Three main factors affect the rate (speed) of diffusion:– Concentration of the diffusing particles– Temperature– Pressure

• If any of these three increases, the diffusion rate will increase. Why?

Factors that Affect Diffusion

Facilitated Diffusion

A. Water can pass easily through the plasma membrane – most substances cannot

B. In facilitated diffusion, special transport proteins move ions and small molecules across the plasma membrane

Transport Processes• Passive transport – movement of a

substance across the plasma membrane without the use of the cell’s energy.

• Active transport – requires the use of the cell’s energy to move substances into or out of a cell across the cell membrane.

Requires Energy

No Energy Required

Cellular Transport Videos

http://www.youtube.com/watch?v=1ZFqOvxXg9M&feature=related

Osmosis is theDIFFUSION OF WATER

Osmosis

• The diffusion of water across a selectively permeable membrane.– Cells must regulate this in order to maintain

homeostasis.– One of three

situations exists.

Figure 7.22 © G

lencoe-McG

raw H

ill (2007)

• http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf

• http://www.youtube.com/watch?v=sdiJtDRJQEc

Isotonic Solution

• Cell is in a solution that has the same concentration of water and solutes Iso – Greek meaning “equal” cell is in dynamic equilibrium

with environment Water enters and leaves the

cell at the same rate.

Figure 7.23 © Glencoe-McGraw Hill (2007)

Hypotonic Solution

• Cell is in a solution that has a lower concentration of solute than the cell hypo – Greek meaning “under” Net movement of water is into

the cell Causes osmotic pressure

In animals – cell could burst In plants, cell wall prevents

bursting; cell becomes firmer

Figure 7.24 © Glencoe-McGraw Hill (2007)

Hypertonic Solution

• Cell is in a solution that has a higher concentration of solute than the cell. hyper – Greek meaning “above” Net movement of water is out

of the cell Results:

In animals – cells shrivel In plants, central vacuole pulls

away from cell wall; plant wilts

Figure 7.25 © Glencoe-McGraw Hill (2007)

Red Blood Cells – A Comparison

• Is your blood pure water?

• What would happen to your red blood cells if pure water were to be injected into your blood stream?

Osmosis ExamplesExample Solution

Pickles are made by immersing cucumbers in a concentrated saltwater solution.

Spraying plants with a solution that contains too high a concentration of fertilizer might cause them to dry out and die.

Patients undergoing surgery are given 0.9% saline (saltwater) solution.

One of the oldest methods of preserving food is to pack them in saline solutions, which kill the bacteria that cause foods to spoil.

Organisms that live in seawater have specialized mechanisms that prevent them from becoming dehydrated.

Florists store fresh flowers in cold water to help the flowers keep their original appearance.