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Cell Biology
Introduction to Cells

CELL BIOLOGY
INTRODUCTION TO
CELLS
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Notes
Highlighting scheme ●

Important words

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Important phrases

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Definitions

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Explanations

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Important statements

UNIT 1
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Cell Theory
a
...


From the 17th century, biologists began to examine plant and animal
tissues using microscopes
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A
theory was devised to explain these common basic structural features
known as the Cell Theory
...


The Cell Theory states that1
...

2
...

a
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The cell is the smallest functional and fundamental unit of life
...


The Cell Theory is still considered a theory because it cannot be
disproven
...


b
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All cells contain or house genetic material, which carries the instructions
for its cellular activities
...


The majority of the cellular activities (chemical reactions) are catalyzed
by the enzymes produced by the cell
...


All living cells are surrounded by a cellular membrane
...


iv
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c
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i
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Striated Muscle Cells- Striated Muscle Cells facilitate movement
...
They also carry their own genetic material and have
their own power-release system
...
3mm)
...

a
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2
...

They usually consist of one cell, yet they can grow to large sizes
...
This challenges the notion that
cells are the smallest functional unit of life, as any large organism
is expected to be multicellular
...
Aseptate Hyphae- Ask Mr
...
Functions of Life
a
...


All living organisms carry out several functions that are necessary for its
survival
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Metabolism -refers to the sum of all the chemical reactions that
take place inside the cell
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Reproduction -refers to the ability of an organism to produce
offspring
...
Growth -refers to an irreversible/ permanent increase in size(dry
mass)
...
Response -refers to the ability to identify and respond to internal
and external stimuli
...
Homeostasis -refers to the process of maintaining a constant
internal environment
...
Nutrition- refers to the process of obtaining food in order to
provide energy such that the organism can function and grow
...
Excretion- refers to the ability to get rid of the waste products
created by metabolism
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Cell Size

a
...


The Arctic fox is twice the size of the Fennec fox
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The metabolic rate of the cell is directly
proportional to its volume
...
The rate of chemical reactions of a cell is directly proportional to
the volume of the cell
...
Why are regular cells microscopic in size?
i
...
What this means is that the rate at which substances
cross the cell membrane depends on the surface area of the cell
...

1
...


c
...

i
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It also has reduced ears such
that it’s body loses heat at a slower rate due to the cold climatic
conditions it lives in
...


ii
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They are
smaller than Polar Bears, and their small size helps them lose heat
...


iii
...


4
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What is Cell Differentiation?
i
...

This is known as the division of labour
...


Cell Differentiation, also known as Cell Specialisation, refers to the
development of cells in different ways such that they can carry out
specific functions
...


iii
...
Therefore, the
key to development lies in the control of genetic expression
...


It allows the tissues to carry out their roles more efficiently than if they
had many different functions
...


b
...


For example, the rod cells and the lens cell of the eye both contain the
gene that gives them the ability to produce a pigment that absorbs light,
however it is only expressed in the rod cells
...
And if the
lens cell did express this gene, less light would pass through the lens and
would blur clarity
...


Another example of differentiation would refer to the olfactory receptor
cells which are only expressed in the skin inside the nose
...

This is how we can distinguish between so many smells
...
Stem Cells
a
...


Stem cells are those cells which have the ability to differentiate into many
different types of cells
...
The sperm fertilizes an egg cell to produce a zygote
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2
...

3
...


b
...


Stem cells have two key properties1
...

a
...

2
...


c
...

i
...

1
...


2
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3
...

ii
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Production of striated muscle fibres, or meat for human
consumption
...
During embryonic development, the cells must commit themselves to a pattern
of differentiation
...
Though they can still divide, they will only differentiate in the same
way and thus, will no longer be stem cells
...
Does the human body have stem cells?
i
...
They have the ability to regenerate and repair
...


UNIT 1
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Prokaryotes and their structure
a
...


Prokaryotes are unicellular organisms that lack a nucleus
...


Instead of a nucleus, prokaryotes have a nucleoid region where
the genetic material is located
...
Describe the structure of a prokaryotic cell
...


Though they are structurally less complex than eukaryotes, prokaryotes
are biochemically complex
...
Prokaryotes are unicellular organisms that lack a nucleus
...

2
...
It has no histones attached to it
...


3
...
However, this
circular piece of DNA can be copied/exchanged/changed
...

4
...
The cytoplasm is the medium for biochemical
reactions
...
A prokaryotic cell lacks cell organelles apart from ribosomes
(Svedberg, 70S)
...
These organisms are encapsulated not only by a cellular
membrane, but also by a cell wall that contains peptidoglycan
...
This cell wall protects the prokaryotic cells from the
external environment, helps it maintain its shape and
prevents it from bursting
...
It is said to be “extracellular”
...
They also have a capsule, which is outside of the cell wall, which
offers them protection
...
The theory states that the capsule goes soft in the summer,
and that is why they can be killed easily by the White blood
cells
...

However, these capsules harden in the winter, and thus are
harder to kill by WBCs, and that is one of the reasons as to
why we are more prone to fall ill in cold climates
...
The cell membrane helps in the regulation of the entry and exit of
materials in the cell
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For movement, prokaryotic cells have Flagella
...
For communication as well as the exchange of materials, the cells
have Pili which are also what they use for response
...


7
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What are eukaryotic cells?
i
...


b
...


Organelles are the compartments within the cytoplasm
...


c
...


Compartmentalisation can be found in eukaryotic cells, where the cell is
partitioned into multiple compartments by single or double membranes
...


The compartments in the cytoplasm are known as organelles, and they
have a definite structure and function
...


The advantages of compartmentalisation are as follows1
...

2
...

3
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a

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