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Is Bigger Better? Comparing Surface area to Volume: (pg. 289 ­ 293)
No matter how big an entire organism gets, its cells remain small. Why do cells stay small??
1. Enables the cell to respond quickly to chemical messages sent by the DNA in the nucleus. 2. Maximizes the cells ability to take in nutrients and minerals such as glucose and oxygen
3. Maximizes the cells ability to quickly eliminate wastes such as carbon dioxide, salts, and nitrogen compounds (urea)
o Small cells are more efficient and have a higher “rate of exchange” of nutrients and wastes with the environment. The chance of survival is better.
o Small cells have a greater surface areas to volume ratio. Because the surface area of cells is cell membrane this means that small cells have greater ability to exchange materials with the outside of the cell.
Find the surface area to volume ratios of the following three cells: A, B, and C.
1 um
2 um
3 um
Cell 1
Cell 2
Cell 3
SA = 6 (s x s) = 6 (1um x 1um) = 6 um2
SA = 6 (s x s) = 6 (2um x 2um) = 24 um2
SA = 6 (s x s) = 6 (3um x 3um) = 54 um2
V = l x w x h = 1um x 1um x 1um = 1 um3
V = l x w x h = 2um x 2um x 2um = 8 um3
V = l x w x h = 3um x 3um x 3um = 27 um3
SA:V ratio = SA :V = 6 : 1 SA:V ratio = SA :V = 24 : 8 = 3 : 1
SA:V ratio = SA :V = 54 : 27 = 2 : 1
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How Does knowing about Cell Transport Benefit Humans
Pg. 284 – 288
Read pg. 286 on “Transport of Protein Hormones” and answer the following questions. 1. What is a hormone?
A small protein that gets excreted into the bloodstream and flows to another cell where it binds to a receptor.
2. Name the hormone produced in the pancreas.
Insulin
3. What is the stimulus that triggers the excretion of this hormone from the pancreas?
Glucose levels (blood sugar) are detected by specialized pancreas cells
4. What active transport mechanism releases this hormone from pancreatic cells?
Exocytosis
5. What does this hormone enable the liver, muscle, and fat cells to do?
Allows muscle, liver and fat cells to store glucose As protein in muscle tissue
As glycogen in liver tissue
As fat in fat tissue
Read pgs. 286 – 287 on “Peritoneal Dialysis” and answer the following questions.
1. What is the function of healthy kidneys in the human body?
To rid the body of toxins, wastes, and excess fluid from the body.
2. What is the peritoneum?
A membrane formed by cells that lines the abdominal cavity.
3. What is the purpose of dialysis? When is it necessary?
Dialysis rids the body of toxins, wastes and excess fluids when the kidneys don’t work properly.
4. Describe the process of “peritoneal dialysis”.
A soft flexible tube (catheter) is inserted into the abdominal cavity. Dialysate solution is pumped into the cavity. Toxins and wastes diffuse across the membrane of the catheter (down the concentration gradient) and enter the dialysate solution. When the solution becomes loaded with waste it is removed from the body.
5. What is the type of transport that is used in dialysis?
Diffusion/Osmosis
6. Is the dialysate (dialysis) solution hypertonic, hypotonic, or isotonic to the waste laden blood? Support your answer.
The solution is hypotonic – means it has less toxins and wastes than the blood so that wastes and toxins move into the solution.
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