RIP BIO CLASS OF 2K17
Biology Study Notes:
1 Cell Biology
1.1 Introduction to cells
The Cell Theory:
I. All living organisms are composed of one or more cells.
II. The cell is the basic unit of structure and organisation in organisms.
III. All cells come from pre-existing cells.
Exceptions to the Cell Theory:
I. Fungi: consists of narrow thread-like structures called hyphae, which
have both a cell membrane and cell wall. Many are divided by cross wall
like structures called septa. Aseptate hyphae don’t have septa and are
long uninterrupted tubes with many nuclei spread along it.
II. Algae: Unicellular and some types (giant algae) can grow to be very large
(up to 100mm).
III. Striated muscle: Much larger than normal animal cells and have an
average length of 30 mm in humans. They are multi-nucleated.
Functions of unicellular organisms:
● Metabolism: chemical reactions inside the cell (respiration etc.).
● Response: Ability to react to stimuli
● Growth: irreversible increase in size.
● Reproduction: producing offspring either sexually or asexually.
● Excretion: getting rid of the waste products of metabolism
● Nutrition: obtaining food to provide energy and the materials needed for
growth.
● Homeostasis: keep internal conditions within tolerable limits.
Paramecium as an example of a unicellular organism:
● Nucleus contains genetic material and divides asexually by mitosis..
● Food vacuoles contain smaller organisms, which are slowly digested; the
products are expelled to the cytoplasm where they are assimilated for
energy and growth.
● Contractile vacuoles store water and expel it to the extracellular to
maintain internal water levels.
● Metabolic reactions are enzyme-regulated and occur in the cytoplasm.
● Cilia control movement of the cell and can be controlled by the cell as a
regulated response to environment stimuli.
● Cell membrane controls movements of substances in and out.
● Excretion occurs by diffusion of substances to the extracellular.
Chlamydomonas as an example of a unicellular organism:
● Nuclear can divide via mitosis. Nuclear can also fuse and divide to carry
out sexual reproduction.
,RIP BIO CLASS OF 2K17
● Metabolic reactions occur in the cytoplasm with the enzymes present.
● Cell wall is freely permeable; cell membrane controls what enters/exists
the cell. Oxygen, waste product, diffuses out of the cell.
● Contractile vacuole maintains internal water levels by expelling water
into the extracellular.
● Photosynthesis occurs in the chloroplasts. Carbon Dioxide is absorbed
from carbon compounds of other organisms.
● Light sensitive eyespot enables detection of light and flagellum facilitates
movement towards light.
Limitations to cells size:
● Surface area to volume ratio is important to be maintained because a
small ratio would slow down the rate of exchange between substances in
the extra/intracellular.
● Waste products would be expelled too slowly and products needed for
cellular reactions would be absorbed too slowly.
● This would result in a built up of waste products as they would be
excreted slower than produced.
● Heat production and loss would also be affected as the cell may over heat,
as it would produce heat faster than it loses it over the cell’s surface.
Multicellular organisms:
● Cells in multicellular organisms can be regarded as cooperative groups.
● Individual cells in a group can work together to form distinctive overall
properties called emergent properties. These arise from the interaction of
the component parts of a complex structure.
Cell differentiation in multicellular organisms:
● Specialised tissues can develop by cell differentiation in multicellular
organisms.
● A group of cells to specialise in the same way to perform the same
function are called a tissue. This allows them to be more efficient.
● There are 220 highly specialised cell types in humans (that have been
recognised so far).
Gene expression and cell differentiation:
● Differentiation involves the expression of some genes and not others in a
cell’s genome.
● All tissues have the same genes, however specialisation involves the
‘turning on’, or expression, of particular genes, which define a specific
function. Differentiation occurs because different sequences of genes are
expressed in different cell types.
Stem cells:
● The capacity of stem cells to divide and differentiate along different
pathways is necessary in embryonic development. It also makes them
suitable for therapeutic uses.
● Therapeutic uses of stem cells include replacing damaged skin tissue and
non-therapeutic uses include formation of striated muscle for human
, RIP BIO CLASS OF 2K17
consumption.
● Stem cells can be found in the bone marrow, skin and liver and can be
used for self-repair.
Use of stem cells to cure Stargardt’s macular dystrophy:
● Stargardt’s macular dystrophy is a genetic disease that develops in
children ages 6-12 years old.
● Recessive mutation of ABCA 4 gene and results in the malfunctioning of a
membrane protein responsible for active transport in retina cells.
● Photoreceptor cell degenerate and vision decays.
● Stem cells are injected into the eye and attach themselves to damaged
cells resulting in improved vision.
Use of stem cells to cure Leukaemia:
● Involves the production of lots of white blood cells at an uncontrollable
rate.
● Chemotherapy kills the dividing cells.
● Adult stem cells are extracted from the bone marrow with a large needle
and then frozen.
● Chemotherapy is then executed and kills cells in the bone marrow.
● Stem cells are then returned to the patient’s body.
Sources of stem cells and the ethics of using them:
Embryonic stem cells Cord blood stem cells Adult stem cells
● Can differentiate ● Easily obtained ● Difficult to obtain
into any type of and stored. because they are
cell. ● Limited buried deep in
● Likely to be differentiation tissues.
genetically capacity and ● Less
different from the develops into differentiation
adult patient. blood cells only. potential than
● Removal of stem ● Umbilical cord is embryonic stem
cells kills the discarded cells.
embryo. regardless. ● Does not kill the
adult from which
they are taken.
1.2 Ultrastructure of cells:
The resolution of electron microscopes:
● Electron microscopes have a much higher resolution than light
microscopes.
● Resolution is making separate parts of an object distinguishable by the
eye. Light microscopes are inhibited by the wavelength of visible light
(400-700nm). Electrons have shorter wavelengths so electron
microscopes have higher resolution.
, RIP BIO CLASS OF 2K17
● Electron microscopes can see viruses and objects up to 1 nm.
● Light microscopes can see objects up to 200 nm.
Prokaryotic cell structure:
● Prokaryotes have no nucleus. They contain a nucleoid with naked DNA.
● They have no compartmentalisation and contain only 70s ribosomes.
● They have no other cytoplasmic organelles (besides plasmids).
● The entire body is filled with cytoplasm, which has several enzymes.
● DNA is not associated with proteins (naked).
● Peptidoglycan cell wall. - for eubacteria, not for archaeans.
● Contains cell membrane.
● Contains flagellum and cilia.
Cell division in prokaryotes:
● Occurs through binary fission. Asexual reproduction.
● DNA replicates (as it does in eukaryotes).
● Copies of DNA move to opposite ends of the cell and then cytoplasm
divides each cell get identical DNA.
Eukaryotic cell structure:
● Complicated internal structure due to compartmentalisation.
● Single/double membrane partitions.
● Contains organelles.
● Compartmentalisation allows:
o Enzymes and substrates to be concentrated to a specific region.
o Damaging substances can be kept within the membrane of an
organelle (lysosome).
o pH levels can be maintained at an ideal level for particular
processes.
o Organelles can be moved around with their contents.
● Nucleus: Nuclear membrane is double and has pores (nuclear pores)
through it. Chromosomes within are tightly coiled DNA around histones.
Chromatin is uncoiled chromosome. DNA replication and transcription
occurs in the nucleus.
● Rough endoplasmic reticulum (rER): Contains cisternae, which are flat
membranous sacs upon which 80S ribosomes are attached. Protein
synthesis occurs here. Proteins pass into cisternae and are carried by
vesicles to the Golgi.
● Golgi Apparatus: Also contains cisternae. Processes and packages proteins
from the rER. Carried in vesicles to the plasma membrane for secretion.
Contents that are being packaged move from CIS to TRANS end.
● Lysosomes: Single membrane. Formed by Golgi vesicles. Contain digestive
enzymes that can break down ingested food or dysfunctional organelles.
● Mitochondrion: Double membrane. Inner membrane invaginated to form
cristae. Fluid inside called matrix. Produce ATP out of glucose/lipids by
aerobic respiration.
● Ribosomes (80S): Synthesise proteins and release them into cytoplasm.
Ribosomes are constructed in the nucleolus, which is present in the
nucleus.
Biology Study Notes:
1 Cell Biology
1.1 Introduction to cells
The Cell Theory:
I. All living organisms are composed of one or more cells.
II. The cell is the basic unit of structure and organisation in organisms.
III. All cells come from pre-existing cells.
Exceptions to the Cell Theory:
I. Fungi: consists of narrow thread-like structures called hyphae, which
have both a cell membrane and cell wall. Many are divided by cross wall
like structures called septa. Aseptate hyphae don’t have septa and are
long uninterrupted tubes with many nuclei spread along it.
II. Algae: Unicellular and some types (giant algae) can grow to be very large
(up to 100mm).
III. Striated muscle: Much larger than normal animal cells and have an
average length of 30 mm in humans. They are multi-nucleated.
Functions of unicellular organisms:
● Metabolism: chemical reactions inside the cell (respiration etc.).
● Response: Ability to react to stimuli
● Growth: irreversible increase in size.
● Reproduction: producing offspring either sexually or asexually.
● Excretion: getting rid of the waste products of metabolism
● Nutrition: obtaining food to provide energy and the materials needed for
growth.
● Homeostasis: keep internal conditions within tolerable limits.
Paramecium as an example of a unicellular organism:
● Nucleus contains genetic material and divides asexually by mitosis..
● Food vacuoles contain smaller organisms, which are slowly digested; the
products are expelled to the cytoplasm where they are assimilated for
energy and growth.
● Contractile vacuoles store water and expel it to the extracellular to
maintain internal water levels.
● Metabolic reactions are enzyme-regulated and occur in the cytoplasm.
● Cilia control movement of the cell and can be controlled by the cell as a
regulated response to environment stimuli.
● Cell membrane controls movements of substances in and out.
● Excretion occurs by diffusion of substances to the extracellular.
Chlamydomonas as an example of a unicellular organism:
● Nuclear can divide via mitosis. Nuclear can also fuse and divide to carry
out sexual reproduction.
,RIP BIO CLASS OF 2K17
● Metabolic reactions occur in the cytoplasm with the enzymes present.
● Cell wall is freely permeable; cell membrane controls what enters/exists
the cell. Oxygen, waste product, diffuses out of the cell.
● Contractile vacuole maintains internal water levels by expelling water
into the extracellular.
● Photosynthesis occurs in the chloroplasts. Carbon Dioxide is absorbed
from carbon compounds of other organisms.
● Light sensitive eyespot enables detection of light and flagellum facilitates
movement towards light.
Limitations to cells size:
● Surface area to volume ratio is important to be maintained because a
small ratio would slow down the rate of exchange between substances in
the extra/intracellular.
● Waste products would be expelled too slowly and products needed for
cellular reactions would be absorbed too slowly.
● This would result in a built up of waste products as they would be
excreted slower than produced.
● Heat production and loss would also be affected as the cell may over heat,
as it would produce heat faster than it loses it over the cell’s surface.
Multicellular organisms:
● Cells in multicellular organisms can be regarded as cooperative groups.
● Individual cells in a group can work together to form distinctive overall
properties called emergent properties. These arise from the interaction of
the component parts of a complex structure.
Cell differentiation in multicellular organisms:
● Specialised tissues can develop by cell differentiation in multicellular
organisms.
● A group of cells to specialise in the same way to perform the same
function are called a tissue. This allows them to be more efficient.
● There are 220 highly specialised cell types in humans (that have been
recognised so far).
Gene expression and cell differentiation:
● Differentiation involves the expression of some genes and not others in a
cell’s genome.
● All tissues have the same genes, however specialisation involves the
‘turning on’, or expression, of particular genes, which define a specific
function. Differentiation occurs because different sequences of genes are
expressed in different cell types.
Stem cells:
● The capacity of stem cells to divide and differentiate along different
pathways is necessary in embryonic development. It also makes them
suitable for therapeutic uses.
● Therapeutic uses of stem cells include replacing damaged skin tissue and
non-therapeutic uses include formation of striated muscle for human
, RIP BIO CLASS OF 2K17
consumption.
● Stem cells can be found in the bone marrow, skin and liver and can be
used for self-repair.
Use of stem cells to cure Stargardt’s macular dystrophy:
● Stargardt’s macular dystrophy is a genetic disease that develops in
children ages 6-12 years old.
● Recessive mutation of ABCA 4 gene and results in the malfunctioning of a
membrane protein responsible for active transport in retina cells.
● Photoreceptor cell degenerate and vision decays.
● Stem cells are injected into the eye and attach themselves to damaged
cells resulting in improved vision.
Use of stem cells to cure Leukaemia:
● Involves the production of lots of white blood cells at an uncontrollable
rate.
● Chemotherapy kills the dividing cells.
● Adult stem cells are extracted from the bone marrow with a large needle
and then frozen.
● Chemotherapy is then executed and kills cells in the bone marrow.
● Stem cells are then returned to the patient’s body.
Sources of stem cells and the ethics of using them:
Embryonic stem cells Cord blood stem cells Adult stem cells
● Can differentiate ● Easily obtained ● Difficult to obtain
into any type of and stored. because they are
cell. ● Limited buried deep in
● Likely to be differentiation tissues.
genetically capacity and ● Less
different from the develops into differentiation
adult patient. blood cells only. potential than
● Removal of stem ● Umbilical cord is embryonic stem
cells kills the discarded cells.
embryo. regardless. ● Does not kill the
adult from which
they are taken.
1.2 Ultrastructure of cells:
The resolution of electron microscopes:
● Electron microscopes have a much higher resolution than light
microscopes.
● Resolution is making separate parts of an object distinguishable by the
eye. Light microscopes are inhibited by the wavelength of visible light
(400-700nm). Electrons have shorter wavelengths so electron
microscopes have higher resolution.
, RIP BIO CLASS OF 2K17
● Electron microscopes can see viruses and objects up to 1 nm.
● Light microscopes can see objects up to 200 nm.
Prokaryotic cell structure:
● Prokaryotes have no nucleus. They contain a nucleoid with naked DNA.
● They have no compartmentalisation and contain only 70s ribosomes.
● They have no other cytoplasmic organelles (besides plasmids).
● The entire body is filled with cytoplasm, which has several enzymes.
● DNA is not associated with proteins (naked).
● Peptidoglycan cell wall. - for eubacteria, not for archaeans.
● Contains cell membrane.
● Contains flagellum and cilia.
Cell division in prokaryotes:
● Occurs through binary fission. Asexual reproduction.
● DNA replicates (as it does in eukaryotes).
● Copies of DNA move to opposite ends of the cell and then cytoplasm
divides each cell get identical DNA.
Eukaryotic cell structure:
● Complicated internal structure due to compartmentalisation.
● Single/double membrane partitions.
● Contains organelles.
● Compartmentalisation allows:
o Enzymes and substrates to be concentrated to a specific region.
o Damaging substances can be kept within the membrane of an
organelle (lysosome).
o pH levels can be maintained at an ideal level for particular
processes.
o Organelles can be moved around with their contents.
● Nucleus: Nuclear membrane is double and has pores (nuclear pores)
through it. Chromosomes within are tightly coiled DNA around histones.
Chromatin is uncoiled chromosome. DNA replication and transcription
occurs in the nucleus.
● Rough endoplasmic reticulum (rER): Contains cisternae, which are flat
membranous sacs upon which 80S ribosomes are attached. Protein
synthesis occurs here. Proteins pass into cisternae and are carried by
vesicles to the Golgi.
● Golgi Apparatus: Also contains cisternae. Processes and packages proteins
from the rER. Carried in vesicles to the plasma membrane for secretion.
Contents that are being packaged move from CIS to TRANS end.
● Lysosomes: Single membrane. Formed by Golgi vesicles. Contain digestive
enzymes that can break down ingested food or dysfunctional organelles.
● Mitochondrion: Double membrane. Inner membrane invaginated to form
cristae. Fluid inside called matrix. Produce ATP out of glucose/lipids by
aerobic respiration.
● Ribosomes (80S): Synthesise proteins and release them into cytoplasm.
Ribosomes are constructed in the nucleolus, which is present in the
nucleus.
