5. Cell Adhesion & Metabolism

Question 1

What is the extracellular matrix? What does it do?

Answer 1

• Cells secrete macromolecules (protein and carbs) into extracellular space, that goes on to form a complex meshwork/scaffold that gives structure to cells and tissues
• Collagen protein is a main component of the ECM
  ex: basal lamina is an ECM secreted by the epithelial cells

Question 2

What is an epithelial cell?

Answer 2

• Cells on the surface (skin, urinary tract, organs, blood vessels). They come into contact with external world.
• All other cells are non-epithelial cells (connective tissue, muscle tissue, nervous tissure)

Question 3

What are connective tissues made of?

Answer 3

• Fibroblasts are main cell found in connective tissues and they secrete collagen proteins
• Overall, connective tissues are mainly made of the extracellular matrix (with some cells embedded)

Question 4

How does the ECM connect to cells?

Answer 4

• The extracellular matrix is directly connected to the cells it surrounds.
• Proteins in the ECM, like fibronectin, connect to integrins (which are embedded in plasma membrane)
• Inside the membrane, integrins are linked to the cells cytoskeleton

Question 5

What are integrins?

Answer 5

• They are proteins embedded in plasma membrane that anchor the cell to the extracellular matrix.
• actin (-) integrin (-) fibronectin
• Recycling of integrins allow cells to move

Question 6

What is a cell’s cytoskeleton composed of?

Answer 6

1. Microfilaments - motion (made of actin protein + myosin)
2. Intermed. filaments- maintain shape (keratin like fibers)
3. Microtubules - maintain shape, help in cell division

Question 7

What are the kinds of cell-to-cell junctions? Why are they needed?

Answer 7

1. Adherens junctions
2. Desmosomes
3. Tight junctions
4. Gap junctions
   Cells must adhere to eachother so that they can assemble into tissues
   note: you can find all four types of adhesions between polarized epithelial cells

Question 8

What’s an apical surface?

Answer 8

The surface of the epithelial cell that faces the ‘outside’ world (exposed to organ cavity or surface of skin)
(have microvilli, which are long brush-like protrusions that increase surface area for diffusion/absorption)

Question 9

What are desmosomes?

Answer 9

• link intermediate filaments between two cells using some ‘cell adhesion molecules’
• link cells tightly (but still room for cells to move around them)
  note: adherens are similar in concept but they link actin microfilaments instead

Question 10

What is ATP (adenosine triphosphate)?

Answer 10

• Unit of energy in cells
• Hydrolysis of ATP releases a large amount of free energy
• it is used to drive unnatural processes (active transport)

Question 11

How does glucose oxidation release chemical energy?

Answer 11

• Through glycolysis (breakdown of glucose by enzymes), which releases energy
• Glycolysis occurs when theres oxygen and no oxygen. When there’s oxygen, cellular resp contines the breaking down of glucose. When there’s no oxygen, fermentation happens

Question 12

What are the three pathways of cellular respiration?

Answer 12

• Pyruvate oxidation
• Citric acid cycle
• Electron transport chain

Question 13

How is energy harvested in the absence of oxygen?

Answer 13

• Glycolysis still occurs

- Instead of cell respiration, fermentation occurs, where a couple small reactions generate lactic acid + some ATP

Question 14

What is an ELISA test?

Answer 14

• To look for the presence of an antigen, protein or antibody

(direct and indirect elisa is looking for antibody, sandwich elisa is looking for antigen of interest)

Question 15

What does aerobic mean?

Answer 15

• Theres oxygen

- Anaerobic means theres no oxygen present