Biology 100/101
Lecture 6:
Cellular Basis of Life
(Print Version)

Announcements &
Assignments

Lecture Objectives

Why Study Cells

Web Resources

Cells Are the
Basic Unit of Life

Prokaryotic Cells

Eukaryotic Cells

Membrane Structure
and Function

Coordination
Organelle Function

Lecture Syllabus

IB 100/101 Home Page

Announcements & Assignments

Text Readings in Life, Lewis et al.

Chapters 4, Cells: Units of Life and 5, the Cell Surface and Cytoskeleton

The "Reviewing Concepts" boxes are valuable summaries of the main ideas in these sections of the text.

You have open access (no log-in or password needed) to instructional materials on the Text web site. Select the text chapter you want and use the links to the e-learning modules or other available materials. There is also a collection of study materials called the "Essential Study Partner" that you may find useful.

Web Crossing

You may also ask questions and see answers to your classmates' questions in Web Crossing in the "Talk to Sarah and Ed" discussion.

Objectives:

The content of today's lecture will help you answer questions 1 and 2 on this assignment:

Take-home Assignment #2, Cells and Membranes, Due At Lecture Monday, September 24

After studying this material you should be able to:

1. Explain how a single cell meets the basic criteria that differentiate living organisms from nonliving objects or chemical reactions.

2. Draw sketches of prokaryotic and eukaryotic cells (plant and animal), pointing out the distinguishing characteristics of each of these types of cells.

3. Describe the basic structure of the membranes in the cells you have drawn and describe the roles of these membranes in determining the organization and functions of cells and their organelles.

Include the following in your description:

phospholipid bilayer	transport proteins	receptor proteins	sugar molecules
diffusion	osmosis	facilitated diffusion	active transport

4. Describe the role of each cell organelle and membrane system involved in the production and secretion of milk from a mammary gland cell. (Read the text section "Organelles Interact to Secrete Substances" starting on pg 54 (Chapter 4 of the Life text). Understand the relationships among the organelles illustrated in figures 4.11, pg. 55)

Include the following in your description:

Chromosomes	DNA	messenger RNA	nucleus
cytoplasm	endoplasmic reticulum (rough & smooth)	ribosomes	protein
vesicles	Golgi bodies	fat droplets	outer cell membrane

As you study the unit on cells, can you figure out how the cell membrane systems, organelles, and other components in the right-hand side of the table below are involved in maintaining the characteristics of living organisms in the left-hand side of the table? (Lecture Objective #1)

Why should we study cells?

• Cells are the basic structures of almost all living things, including us. There are maybe 10 to 100 trillion of them in each of our bodies.

• Cells do all the chemical activity that happens in our bodies (our meaning - all types of organisms).

• They process energy, digest our food, capture CO2, release CO2, release heat

• When cells get "out of whack" we get sick.

• Cancer Cells

• Stem cells may one day help us recover from inherited and other types of illness or injury.

• The hard cell Ethical quandaries aside, stem-cell science is attracting researchers worldwide. Ricki Lewis reports. (an article by Ricki Lewis your text author, at nature.com.)

• Stem Cell Basics from the National Institutes of Health

Cell Biology Web Resources

• Virtual Cell by Matej Lexa, Plant Biology, UIUC

• The Virtual Cell Biology (Different from above)

• Cells Alive great pictures and movies

• Cell Structure Illustrations from geneticsolutions.com

Cells as the "Basic Unit of Life"

• Cells are common to all organisms from bacteria to fungi, plants, and animals.

• Cells were "discovered" as the basic unit of living organisms in the nineteenth century.

• Early observations of cells led to the distinction of two major cell types:

• Prokaryotes - cells without membrane-bound nuclei or other cell organelles.

• Bacteria

• Eukarya - cells with "true" nuclei and membrane-bound organelles

• Plants, Algae, Fungi, Animals, you and me

• A third cell type - characteristic of another domain of life was discovered by Carl Woese wins Crafoord Prize! at the University of Illinois in 1977.

• Archaea - cells similar to bacteria in that they do not have membrane-bound nuclei or other cell organelles, BUT they differ genetically and in other structural characteristics. Many Archaea have been found in extreme environments (temperature, pressure, salinity).

• Archaea, bacteria, and eukaryotic cells are all thought to have evolved from some common ancestor.

Prokaryotic Cells

• Pro = before, karyon = kernal (what nuclei looked like to those who first saw them through a microscope)

• Cells WITHOUT ORGANIZED NUCLEI bounded by a nuclear membrane OR ANY OTHER MEMBRANE-BOUND ORGANELLES

• Eubacteria (True bacteria) (Text pg. 50, fig. 4.6) and cyanobacteria (blue-green algae)

• No membrane bound organelles within the bacterial cell

• Nucleoid - the main genetic content of the cell

• Electron micrograph of Bacterial Cell with nucleoid

• Electron micrograph of DNA of bacterial cell with plasmids

• Plasmids are small circular pieces of DNA that are separate from the DNA of the nucleoid.

• Test your knowledge of prokaryote structure.

• Bacterial structure illustration (Illustration from Dr. Richard G. Steane )

Eukaryotic Cells

• Eu = true, karyon = kernel (nucleus)

• Cells WITH ORGANIZED NUCLEI bounded by a nuclear membrane AND OTHER MEMBRANE BOUND ORGANELLES.

• Plants and animals HAVE EUKARYOTIC CELLS

• Animal Cell - Text, page 53 fig. 4.9

• Plant Cell - Text, page 54 fig. 4.10

• Nucleus - Text, page 56 fig. 4.12

• Endoplasmic Reticulum - Text, page 56 fig. 4.13

• Golgi bodies - Text, page 57 fig. 4.14

• Mitochondria and Chloroplasts later

• Fungi, algae, and most other types of organisms, except bacteria and archaea

• All have a cell (plasma) membrane

• Some have cell walls

Membrane Structure and Function

• Membranes are selectively permeable structures that regulate the movement of molecules in and out of the cell (bacteria, archaea, and eukaryotes) and in and out of compartments within the eukaryote cell.

• The basic structure is a phospholipid bilayer. Phospholipid molecules align to form membranes because part of the molecule is hydrophilic (the phosphate end) and part is hydrophobic (the fatty acid chain). (Text pg 67, fig 5.2)

• The Phospholipid bilayer is a constantly moving, fluid structure. Proteins and other materials imbedded in it are free to move about.

• Proteins embedded within the membrane perform many tasks: (Text pg 68, fig. 5.3)

• Receptor proteins: receive and transmit chemical messages so that cells can respond to changes in their environment.

• Cells respond to hormones produced in your body when hormone molecules bind to specific receptor proteins in your cell membranes. (Insulin, growth hormone, sex hormones, thyroid hormones, etc.)

• Antihistamines block the receptor proteins that normally bind histimines produced when you have an allergic reaction to something in your environment. (Link from wikipedia.org)

• Cell surface proteins: Important for recognition of self (in animals). Your blood type and tissue type are determined by the proteins on the surface of your cells. This is especially important to consider when getting a transfusion or a tissue or organ transplant.

• Transport proteins: move substances across the membrane

How do materials cross membranes?

• Membrane transport proteins (Text pg 71 fig. 5.9)

• PASSIVE TRANSPORT (no energy needed):

• Diffusion: Movement of molecules from high to low concentrations. (eg oxygen, carbon dioxide).

• Osmosis: Movement of water from low to high solute (salt) concentrations.

• Facilitated transport: Movement across the membrane via a protein channel

• ACTIVE TRANSPORT (need to expend energy):

• Pumping of ions or molecules across the membrane and from low to high concentrations using the energy from ATP (produced by respiration) and carrier proteins

• Exocytosis (Text pg. 73 fig. 5.12)

• Endocytosis (Text pg. 74 fig. 5.13)

• Ricin - a deadly ribosome toxin enters the cell by endocytosis

Eukaryotic cells are thought to have developed from the symbiotic relationship of one cell being engulfed by another cell, but not being digested - the endosymbiotic hypothesis

Coordinating organelle function:
Example of the production of breast milk (Lewis page 55, Figure 4.11)