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Higher Human Biology
Unit 1
Human Cells
KEY AREA 1: Division & Differentiation
Higher Human Biology
We are going to build on the knowledge and skills that you developed during N5 and will
learn about the following Human Cells key areas : -
Key Area 1 – Division & Differentiation
Key Area 2 – Structure & Replication
Key Area 3 – Gene Expression
Key Area 4 – Health & Disease
Key Area 5 – Human Genomics
Key Area 6 – Metabolic Pathways
Key Area 7 – Cellular Respiration
Key Area 8 – Energy Systems
Human Cells Learning Intentions
KEY AREA 1 – Division & Differentiation
a) Differentiation
b) Stem Cells
c) Somatic Cells
d) Germline Cells
e) Research & Therapeutic Uses of Stem Cells
f) Cancer Cells
1a) Differentiation
a) DIFFERENTIATION
Cell differentiation is when an unspecialised cell
becomes specialised to carry out a specific
function (e.g. a basic animal cell becoming
specialised into a goblet cell in the trachea)
A cell becomes specialised by the switching on
and switching off of specific genes – this is
called gene expression
Once a cell becomes differentiated it only
expresses the genes that produce proteins
characteristic for that type of cell
Examples of differentiated cells are sperm
cells, goblet cells, nerve cells, red blood cells,
1b) Stem Cells
Stem cells are cells that are unspecialised and have the ability to differentiate
into specialised cells
1c) Stem Cells have 2 roles
Stem cells are different from other cells of the body because stem
cells can:
1. SELF-RENEW (Make copies of themselves)
AND
2. Differentiate (Make other types of cells)
1d) Different Types of Stem Cells
There are 2 different types of STEM CELLS:1. Tissue Stem Cells (also called Adult Stem Cells)
2. Embryonic Stem Cells
1e) Where do we find Embryonic Stem Cells?
Embryonic Stem Cells are found in a human blastocyst
ALL of the genes in an Embryonic Stem Cell have the ability to be switched on
Embryonic Stem Cells can make ALL types of differentiated cells (pluripotent)
1f) Where do we find Tissue Stem Cells?
Tissue Stem Cells are found in the brain,
skin, testicles, bone marrow, breast,
intestines, muscles, surface of the eye
(cornea)
Some of the genes in a tissue stem cell have
already been switched off which means
Tissue Stem Cells produce a limited range
of cell types
Tissue Stem Cells are multipotent (can
make SEVERAL types of differentiated
cells)
Tissue (adult) stem cells replenish
differentiated cells that need to be
replaced
Example of Tissue Stem Cells
are stem cells in bone marrow
which can differentiate into
different types of blood cells
(e.g. red blood cells, platelets,
phagocytes and lymphocytes)
1g) Stem Cells & Medical Treatments
1h) Somatic Cells
The scientific name for a body cell is a Somatic Cell
All differentiated cells (except gametes) arise from Stem
Cells and are called Somatic Cells
Somatic Cell
(e.g. Cheek Cell)
Diploid (2 sets of
chromosomes)
Somatic cells divide by mitosis to form more somatic cells
Each somatic cell contains 46 chromosomes and is diploid (2
sets of 23chromosomes)
Cell Division
(Mitosis)
Somatic cells differentiate to form different body tissue
types; epithelial, connective, muscle and nerve
Body organs are formed from a variety of tissues working
together
Epithelial cells cover the body surfaces and line body cavities
Blood, bone, and cartilage cells form connective tissue
Muscle cells form muscle tissue
Nerve cells form nervous tissue
Mutations in somatic cells are not passed to offspring
New Somatic Cells
(cheek cells)
Diploid (2 sets of
chromosomes)
1i) Germline Cells
The scientific name for a cell that produces
gametes is a Germline Cell
In humans, germline cells are found in the ovaries
and testes
Germline cells can divide by meiosis to produce
gametes (haploid) cells
Mutations in germline cells are passed to
offspring
Germline cells can divide by mitosis to produce
more germline (diploid) cells
Germline Cell in Ovary
(Diploid)
Cell Division
(Meiosis)
New Egg Cell
(Haploid – 1 set of
chromosomes)
1j) Human Life Cycle
1k) RESEARCH & THERAPEUTIC USES OF STEM CELLS
Stem cell research provides information on how cell processes such as cell growth,
differentiation and gene regulation work.
Stem cells can be used for repairing damaged or diseased organs or tissues e.g. corneal
transplants, skin grafts for burns
Stem cells can be used as model cells to study how diseases develop or for drug testing
Law/Regulations. Stem Cell use is regulated. Embryonic cells must not be allowed to
develop beyond 14 days, around the time a blastocyst would be implanted in a uterus
1l) Embryonic Stem Cell Ethical Debate
AGAINST using Embryonic Stem Cells
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A human life begins with a fertilised egg and
it should not be harmed
A fertilised egg is a human being with a soul
Stem cell research is unnatural
FOR using Embryonic Stem Cells



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A fertilised egg is not a person, although it
has the potential to develop into a person
At 14 days or less, the fertilised egg has
developed into an embryo but it does not have
a brain, or nervous system or any “feelings”
A foetus can be terminated at up to 20weeks,
so destroying a 14day old embryo seems less
objectionable
Stem Cell Research has the potential to
benefit millions of people with medical
conditions
Stem Cell Research uses Embryos that were
generated for IVF but were not used & would
be destroyed anyway
Possible solution to the Embryonic Stem Cell Debate:Use Induced Pluripotent Stem Cell (IPS) – these are stem cells created from reprogramming
differentiated cells back to an embryonic state
Problem with IPS Cells – viruses used in the procedure cause cancers in mouse models, so more
research needs to be done on IPS cells
1m) Cancer Cells
Cancer cells divide excessively to produce a mass of abnormal cells called a tumour.
Tumour cells do not respond to regulatory signals and may fail to attach to each other.
Secondary Tumours form if cancer cells fail to attach to each other so they spread
through the body (metastasis)
Metastasis is the spread of cancer from its primary site to other places in the body
Human Cells Questions
KEY AREA 1 – Division & Differentiation
1. Testing Your Knowledge 1
Page 8
Q’s 1-4
2. Testing Your Knowledge 2
Page 15
Q’s 1-3
3.
Quick Quiz