Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

11. Cell Division

Introduction to Cell Division

General Biology

11. Cell Division

Introduction to Cell Division

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1:49 minutes

Problem 20

Textbook Question

Red blood cells, which carry oxygen to body tissues, live for only about 120 days. Replacement cells are produced by cell division in bone marrow.
How many cell divisions must occur each second in your bone marrow just to replace red blood cells? Here is some information to use in calculating your answer: There are about 5 million red blood cells per cubic millimeter (mm³) of blood. An average adult has about 5 L (5,000 cm³) of blood. (Hint: What is the total number of red blood cells in the body?
What fraction of them must be replaced each day if all are replaced in 120 days?

Verified step by step guidance

Calculate the total number of red blood cells in the body by multiplying the concentration of red blood cells (5 million cells per mm³) by the total blood volume in mm³. Convert the blood volume from liters (5 L) to mm³ using the conversion factors: 1 L = 1,000 cm³ and 1 cm³ = 1,000 mm³.

Determine the number of red blood cells that need to be replaced each day by dividing the total number of red blood cells by 120 (since red blood cells live for 120 days).

Calculate the number of red blood cells that must be replaced each second by dividing the daily replacement number by the number of seconds in a day (24 hours × 60 minutes × 60 seconds).

Recognize that each cell division produces two daughter cells. Therefore, determine the number of cell divisions required per second by dividing the number of red blood cells replaced per second by 2.

Summarize the process: The total number of red blood cells is calculated, the daily replacement rate is determined, the replacement rate per second is found, and the number of cell divisions per second is calculated by accounting for the fact that each division produces two cells.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Red Blood Cell Lifespan

Red blood cells (RBCs) have a lifespan of approximately 120 days in the human body. After this period, they are removed from circulation and must be replaced. Understanding this lifespan is crucial for calculating the rate of RBC production needed to maintain adequate oxygen transport in the body.

Bone Marrow Function

Bone marrow is the primary site of hematopoiesis, the process of blood cell formation, including red blood cells. It produces new RBCs through cell division, ensuring that the body maintains a sufficient supply to replace those that are lost. This concept is essential for understanding how the body compensates for the continuous turnover of blood cells.

Cell Division Rate Calculation

To determine how many cell divisions occur each second in the bone marrow, one must calculate the total number of RBCs in the body and the daily replacement rate. Given that an average adult has about 5 liters of blood containing approximately 5 million RBCs per cubic millimeter, this calculation involves understanding volume, concentration, and time to find the necessary production rate.

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Related Practice

Textbook Question

Which of the following is not a function of mitosis in humans?

a. Repair of wounds

b. Growth

c. Production of gametes from diploid cells

d. Replacement of lost or damaged cells

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Textbook Question

Mitosis ________.

a. Occurs only in cancerous cells.

b. Occurs only in skin cells.

c. Produces daughter cells that are exact genetic copies of the parent cell.

d. Results in the production of three different cells.

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Textbook Question

It took three sheep to create the clone Dolly: A blackface sheep donated the egg, a whiteface sheep donated the mammary cells from which the nucleus was taken, and a blackface sheep served as surrogate. Assuming face color is genetically determined, what color face did Dolly have?

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Textbook Question

Each scientist works as part of a broader community of scientists, building on the work of others. Scientific advances often depend on the application of new technologies and/or on new techniques applied to an existing problem.

What improvements to existing cloning methods did Wilmut make that allowed him to successfully clone Dolly the sheep from an adult cell?

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Multiple Choice

Why is it important that a cell's DNA is duplicated before cell division?

311

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Multiple Choice

Why is cell division important for both single-celled and multicellular organisms?

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Multiple Choice