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2.1.1 Mitosis as Part of The Cell Cycle

(a) The Cell Cycle

(b) DNA

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(c) DNA Replication

1. The DNA molecule unwinds and
unzips. The enzyme DNA
helicase causes the hydrogen
bonds between base pairs to

2. new DNA nucleotides pair up
with the exposed bases,
according to the
complementary base pairing

3. The nucleotides are joined
together by the enzyme DNA…

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(f) Apoptosis
Apoptosis is triggered cell suicide. The cell shrinks, the dna and protein in the nucleus breaks down. The
mitochondria break down. The cell breaks up into small fragments wrapped in membrane. A
phospholipid, phosphatidylserine, normally on the outside is place on the inside. Phagocytic cells such as

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(k) Stem Cells
A cell that can remain undifferentiated and divide to form different kinds of cells are called stem cells.

(l) Differentiation
When cell types remain different they are said to be differentiated. This means that some genes within
the cell are switched off. Once a cell has differentiated…


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