Cambridge AS & A Level Biology Cells Lesson 1

Cambridge AS & A Level Biology Cells Lesson 1

1. Biology

2. Lynn Margulis

3. A mid-19
th
century idea

New organisms can be created from
combinations of existing organisms.
The existing organisms may not be
closely related!

Symbiosis
Endosymbiosis

4. Symbiosis

5. Demodex mites

6. Endosymbiosis

7. Robert Hooke's cork cell

8. Schleiden and Schwann

9. 2 Types of Cells

Simple cells

DNA not surrounded by
membranes

Complex cells

Contains a nucleus (or nuclei)
surrounded by 2 membranes

DNA is in the nucleus

10. cell:
the basic unit of all living
organisms;
it is surrounded by a cell surface
membrane and contains genetic
material (DNA) and cytoplasm
containing organelles

11. organelle:
a functionally and structurally
distinct part of a cell, like a
ribosome or mitochondrion

12. Nucleus (nuclei):
a relatively large organelle found in
eukaryotic cells, but absent from
prokaryotic cells; the nucleus
contains the cell’s DNA and
therefore controls the activities of the
cell; it is surrounded by two
membranes which together form the
nuclear envelope

13. eukaryote:
an organism whose cells
contain a nucleus and other
membrane-bound organelles

14. prokaryote:
an organism whose cells do
not contain a nucleus or any
other membrane-bound
organelles

16. Microscopy
The smallest structure visible with the human eye is
about 50–100 μm in diameter (roughly the diameter of
the sharp end of a pin). The cells in your body vary in
size from about 5 μm to 40 μm. An average bacterial cell is
about 1 µm across.. One of the smallest structures you
will study in this book is the ribosome, which is only
about 25 nm in diameter! You could line up about
20 000 ribosomes across the full stop at the end of
this sentence.

19. Compare and Contrast

20. What do plant cells and animal cells
have in common?

Cell surface membrane

(partially permeable)

Nucleus

Cytoplasm

Mitochondria

21. What is different between plant cells
and animal cells?

Animal cells can have
centrioles.

Plant cells have cell walls.

Plant cells have permanent
vacuoles.

Plant cells have chloroplasts.

22. Draw and label a cell.