1.1: Introduction to cells
Teaching time: 2 hours Practical time: 2 hours
NB - some of the applications and understanding of this topic we cover in the DP Biology introduction:
A2: Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
U2: Organisms consisting of only one cell carry out all functions of life in that cell.
key vocabulary
Prior learning and retrieval practice
Review the functions of life in a paramecium
Cell Theory
U1: According to the cell theory, living organisms are composed of cells.
Exercise 1: Think-Puzzle-Explore
What do you think you know about cells?
What questions or puzzles do you have about cells?
How could we explore these questions or puzzles?
Exercise 2: Now try to complete this true or false quiz:
1. All cells are the same size and shape.
2. There is a generic animal or plant cell.
3. There are no single celled organisms.
4. Cells come from pre-existing cells.
5. Some living parts of organisms are not made of cells.
6. Plants are not made of cells.
7. Cells of living organisms do not make molecules for their own growth and repair.
8. Animal cells do not eliminate their own wastes.
9. Bacteria do not extract energy from food.
10. Bacteria do not need food to function.
11. Cells are the smallest unit of life.
12. Organisms grow by cell division but the cells themselves do not increase in size or mass.
13. The leaves of plants cannot develop from a single fertilized cell.
14. Living organisms are composed of cells.
15. Different cells can have different shapes and sizes.
16. Cells are organized into the body structures and perform the basic life functions of the organism they are part of.
17. The inside of an animal cell contains water as well as solid structures.
Exercise 3: Now read the relevant section of your textbook and connect-extend-challenge.
Exercise 4: Outline the cell theory.
A1: Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
NoS: Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. (3.1)
Exercise 5: Answer these questions:
What organisms are atypical of the cell theory?
For each organism, what structures are atypical?
How might each of them suggest that the theory is not quite correct?
Multicellular organisms and cell differentiation
The Essential Idea: The evolution of multicellular organisms allowed cell specialisation and cell replacement.
U3: Surface area to volume ratio is important in the limitation of cell size.
Exercise 6: Watch the video on the right and complete this exercise:
Cubic cells of increasing size: For imaginary cells with sides of 1, 2, 4 and 6mm:
1. Calculate the volume, surface area and ratio of the surface area to volume for each.
2. State the effect on the SA:Vol of a cell as it increases in size.
3. Explain the effect of increasing cell size on the efficiency of diffusion in the removal of waste products from the cytoplasm.
4. How might organisms overcome the problems of large cell sizes?
U4: Multicellular organisms have properties that emerge from the interaction of their cellular components.
U5: Specialized tissues can develop by cell differentiation in multicellular organisms.
U6: Differentiation involves the expression of some genes and not others in a cell’s genome.
Exercise 7: Read the relevant section of your textbook and connect-extend-challenge.
Stem cells
A3: Use of stem cells to treat Stargardt’s disease and one other named condition.
U7: The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.
A4: Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues.
Nature of Science Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5)
Exercise 8: In your groups prepare a 10 minute presentation on the uses and ethics of stems cells.
In your presentation cover:
a) The different types of stem cells (embryonic vs adult; totipotent, multipotent and pluripotent)
b) Examples of two diseases that could potentially be treated with Stem cells (one must be stargardts disease)
c) The ethics of using adult vs embryonic stem cells.
You may ONLY use these two sources and they must be properly referenced:
Source 1: https://nei.nih.gov/health/stargardt/star_facts (Last three paragraphs relate to Stem cell therapy)
Source 2: https://drive.google.com/a/gwe.gemsedu.com/file/d/0B9ZfdBKx0IKCSnRWVVdQUjZzQ0E/view?usp=sharing
Practical 1
S1: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
