Lecture 4

Front 1

1. Cell mass is a combination of what two factors?

Back 1

Cell size + Cell number (which is a balance between cell division & cell death)

Front 2

2. What is the difference between necrosis and programmed cell death?

Back 2

Necrosis: premature cell death – cell death that does not occur of natural causes (disease, injury, starvation, toxicity, excitotoxicity)
Programmed cell death: cell death that is designed to happen (apoptosis, anoikis, cornification, autophagy)

Front 3

3. What are the key functions of the ECM?

Back 3

Mechanical support & defense
Adhesion for cells & tissues
Substrate for cells & organismal movement
Regulation of cell growth & function

Front 4

4. Most organisms use a combination of carbohydrates and proteins to build their ECM and may use inorganic molecules to harden their ECM. How do vertebrates differ from arthropods? How do plants differ from prokaryotes?

Back 4

Vertebrate ECM: two main types of macromolecules – Fibrous proteins & GAG polysaccharides and proteoglycans (& Ca2+ Apetite – bone)
Arthropods: Chitin, fibrous protein matrix (leathery structure) and Ca2 carbonate (hardening agent)
Plants: cell wall -> cellulose & pectin
Prokaryotes: cell wall -> peptidoglycan (Bacteria) or pseudopeptidoglycan (Archaea)

Front 5

5. What are biofilms? And what is the ECM of biofilms called and composed of? How is the composition of biofilm ECM different from the ECM of a single bacterium?

Back 5

Biofilm: slimy films of bacteria that adhere to surfaces -> adherent, differentiated & cooperative cells
ECM components: extracellular polymeric substance (DNA, proteins, polysaccharides)
Different from single bacterium because they adhere to one another, become differentiated for specialized functions & cooperate via cell-cell signaling

Front 6

6. What are the main purposes of cell-cell communication for single-celled and multi-cellular organisms?

Back 6

Purpose: to detect & respond to a signal in the environment
Single-celled: adapt gene expression/metabolism, mating, sporulation & cell death in response to pop. density, nutrient availability, stress & other cues
Multi-cellular: coordinate activities of multiple cells in response to needs of organism as a whole

Front 7

7. What is quorum sensing?

Back 7

Quorum sensing is done by bacterial colonies in biofilms
Single-cells use to sense their environment
Ancestral form of cell signaling that many of today’s pathways have evolved from

Front 8

8. Describe a generalized signal transduction pathway.

Back 8

Signaling molecule binds to cell-surface receptor protein
Signal transduced through intracellular signaling proteins
Variety of effector proteins induce some cellular change, such as metabolism, gene expression, altered cell morphology or cell migration
Proteins sequentially modify one another

Front 9

9. Describe the five different types of cell-cell signaling.

Back 9

1. Contact-dependent (juxacrine): cell signaling to directly neighboring cell
2. Paracrine signaling: cell signaling to localized cells through ECM
3. Synaptic signaling: neurons that transmit signals electrically along axons & release neurotransmitters at synapses
4. Endocrine signaling: endocrine cells secrete hormones into bloodstream for whole-body distribution
5. Cytosolic sharing: signaling molecules travel through cytoplasmic channels (gap junctions/plasmodesmata (plants)) through intervening cells walls or membranes

Front 10

10. If every cell in an organism contains the same DNA, why aren’t all cells the same? (i.e., How can they have such different qualities and perform different functions if they all contain the same DNA?)

Back 10

Cells are not all the same because they are of different cell types, as they are specialized for different functions
Differential gene expression/regulation allows for some genes to be expressed in some cells & not in others, resulting in different functions

Front 11

11. Describe the anatomical organization of multicellular organisms. How is it organized and what is it based on?

Back 11

Anatomical organization is dependent upon specialized cell functions
Organization based upon multiple tissue types
Cells -> tissues -> organs -> systems

Front 12

12. What is the difference between epithelial and mesenchymal cells?

Back 12

Epithelial: cells connected in a sheet or tube; forms the inner & outer linings of organs
Mesenchymal: loosely-packed cells with abundant ECM

Front 13

13. What is the difference between parenchymal and stromal cells?

Back 13

Parenchymal: distinguishing cells of a gland or organ
Support (stromal) cells: from the connective tissue in organs

Front 14

14. What is the difference between stem cells and differentiated cells?

Back 14

Stem cells: undifferentiated, unspecialized cells with the ability to self-renew and form specialized cells
Differentiated cells: terminally differentiated, post-mitotic cells with a specialized function

Front 15

15. If a cell was removed from its tissue, could it still function in the same manner? Explain.

Back 15

Probably not. Cells need signaling from the organism to regulate its metabolism, gene expression, etc.