Cell Biology
By Madelief and Rambo
1.1 Introduction to cells
Outline of the three components of cell theory
Illustration by Hugo Lin From ThoughtCo.
Outline of exceptions to cell theory
Striated Muscle
;a type of tissue made out of muscle
fibres, which are somewhat similar to
cells in that they are surrounded by a
membrane, and are formed by pre-
existing cells.
However, the fibres are far from typical,
as they are much larger than most
animal cells. Instead of having a single
nucleus, they might have as many as
several hundred within one “cell”.
Aseptate Fungal Hyphae
;consist of narrow thread-like structures
called hyphae. These are usually white
in colour and have a fluffy appearance.
They have a cell membrane as well as a
cell wall. In some types of fungi, the
hyphae are divided into small cell-like
sections by cross walls called septa.
But in aseptate fungi there are no
septa; each hypha is an uninterrupted
tube-like structure with many nuclei
spread along it
Giant Algae
;organisms that feed themselves by
photosynthesis and store their genes
inside nuclei. Usually algae consist of
one microscopic cell but some algae
grow to a much larger size, yet they
still seem to be single cells.
Acetabularia is one example; it can
grow to a length as much as 100mm,
despite only having one nucleus and
any organism with a length of 100mm is
expected to be multicellular.
Illustration from BioNinja:Cell Theory
Calculation of magnification of drawings or micrographs
When using the equation, make sure that the units for the size of the image and the size of the specimen are the same.
They could be in millimeters (mm) or micrometers (µm) but they must not be different or the calculations will be wrong.
Scale bars are sometimes put on micrographs or drawings in exams. These are straight lines, with the actual size that the
scale bar represents.
Cool website: https://learn.genetics.utah.edu/content/cells/scale/
Functions of life
Unicellular organisms carry out at least seven functions of life
Metabolism: chemical reactions inside the cell, including cell respiration to release energy
Reproduction: producing offspring either sexually or asexually
Growth: an irreversible increase in size
Response: the ability to react to changes in environment
Excretion: getting rid of the waste products in metabolism
Homeostasis: keeping conditions inside the organism within tolerable limits
Nutrition: obtaining food, to provide energy and the materials needed for growth
AKA Mr. Grehn
Paramecium and Chlamydomonas
Paramecium is a unicellular organism that can be cultured quite easily in the laboratory.
Alternatively, collect some pond water and use a centrifuge to concentrate the organism
in it to see if Paramecium is present.
Chlamydomonas is a unicellular algae that lives in soil and freshwater habitats.
It has been used widely for research into cell and molecular biology.
Although it is green in colour and carries out photosynthesis it is not a
true plant and its cell wall is not made out of cellulose.
As the cell gets bigger,
Relationship between size and surface area: volume ratio
