year 1 biology chapter 2 revision
TRANSCRIPT
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2.1.10 Outline one Therapeutic use of Stem Cells
Stem cells are cells that have yet to be specialised and have the ability to repeatedly
divide and differentiate into various cell types.
Adult stem cells can divide an unlimited amount of times, producing a new stem cell and a
new body tissue each time. (i.e. blood stem cells present in our bone marrow produce a
full range of different types of blood cell) . in fact stem cells can grow into any of the 300
different types of cells found in the human body.
Stem cell research seeks to use the human embryonic stem cells, obtained for embryos
only a few days old. These cells are more flexible in that they may be coaxed to grow into
any type of mature cell. ES cells may be extracted from human embryos that have been
discarded during fertility treatment. Therapeutic cloning is the creation of human
embryos for the sole purpose of producing ES cells rather than cloning to produce a new
human being.
The hope is that the ES cells that have been grown within a laboratory, will be able to help
cure patients to treat diseases like Alzheimers, Parkinsons or Type 1 diabetes. It is also
hoped the genetically engineered stem cells could eventually be able to treat the genetic
fault underlying sickle cell disease.
Those patients with cystic fibrosis might be treated but removing their own stem cells and
genetically modifying them with the cystic fibrosis gene. The cells then would be planted
back in the patient in a way that may lead to the formation of healthy cells lining the
airways. This would eliminate the problem of tissue rejection that occurs in transplant
surgery.
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2.2 Prokaryotic Ce
s
Unit
2 2 2 Annot
t
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p o
ot
ith th
fun
tionsof
h st u
tu
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d
2 2 4
t
t
th
t p o
oti
ll di
id
b
bin
fission
Binary fission is the process where DNA replicates which is followe by theseparation of
DNA and thecell.
Cell Wall- provides protection from
physical damage maintainsshape
and reventse
cess water u take.Flagellum/ flagella- allow
thecell to move.
Fimbria- also called pili.
Used to stick to another cell
and inanimate objects
Cell membrane controls theentry of raw
materials into thecell. Acts as a boundary layer
to contain thecytoplasm interlocking surface
that bindscells together
Plasmids-e
tra chromosomal
DNA. Can replicate
independently from
chromosomal DNA
Ribosome site of
rotein s nthesis.
DNA (genetic material)- nucleic acid that
contains genetic instructions used in the
development and functioning of living
organisms.
Capsule-
Binary fission begins with DNA replication. DNA replication starts
from an origin of replication, which opens up into a replication
bubble. The replication bubbleseparates the DNA doublestrand,
each strand acts as template for synthesis of a daughter strand
bysemi conservative replication, until theentire prokaryotic DNA
is duplicated.
After this replication process, cell growth occurs.
Each circular DNA strand then attaches to thecell membrane.
Thecell elongates, causing the two chromosomes to separate.
Cell division in bacteria iscontrolled by the FtsZ, a collection of
about a dozen proteins that collect around thesite of division.
There, they direct assembly of the division septum. Thecell wall
and plasma membranestarts growing transversely from near the
middle of the dividing cell. Thisseparates the parent cell into two
nearlye
ual daughter cells, each having a nuclear body.
Thecell membrane then invaginates (grows inwards) and splits
thecell into two daughter cells, separated by a newly grown cell
plate.
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2.3 Eukaryotic Cells
Unit
2.3.1 Draw and label a diagram of the ultrastructures of a liver cell
2.3.3 Identify structures in a eukaryotic cell. (know there functions)
Organelle Function Plant/Animals Prokaryotic/Eukaryotic
Nucleus The control centreDNA is dispersed in the cellEncloses DNA
Y/Y N/Y
Chloroplast Site of photosynthesis and storage ofstarch.
Y/N N/Y
Mitochondria Removes unwanted structural debris.Energy-supplying organelle.Produces ATP and the site of aerobicrespiration
N/Y N/Y
Ribosomes Site of protein synthesis. Y/Y Y/Y
Cilia & Flagella For a single cell it allows them to swim.For cells anchored in a tissue movesliquid over the surface of the cell.
Y/Y Y/Y
Golgiapparatus
It stores and later transports the proteins Y/Y N/Y
Endoplasmicreticulum
Series of membranous channels fortransport inside the cell.Channels through which the newly madeprotein is moved within the cell.
Y/Y N/Y
Cytosol Its a structure element of the cell.Protects the cell from germs and dirt.
Y/Y Y/Y
Cell wall Provides protection from physical
damage.Semi-rigid, protective structure depositedby the cell outside the cell membrane.Maintains the shapePrevents excess water uptake
Y/N Y/Y
Cell membrane The structure that controls the entry ofraw materials into the cell.Acts as a boundary layer to contain thecytoplasm.Interlocking surface that binds cellstogether.
Y/Y Y/Y
Vacuole removes unwanted debris, isolates Y/Y N/Y
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harmful material and maintains moleculesLysosomes Lysosomes contain enzymes that help to
break up food so it is easier to digest.N/Y N/Y
Centrioles Centrioles are a very important part
of centrosomes, which are involved
in organizing microtubules in the
cytoplasm. The position of the
centriole determines the position of
the nucleus and plays a crucial role
in the spatial arrangement of the
cell.
N/Y N/Y
2.3.4 Compare prokaryotic and eukaryotic cells
Prokaryotic
(e.g. bacteria)
Feature Eukaryotic
(e.g. animals, plants, fungi)
Cells are extremely small, SIZE Cells are larger, typically 50-150m
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typically 5-10m
Nucleus absent; circular
strand of DNA helix in the
cytoplasm.
GENETIC
MATERIAL
Nucleus has a distinct nuclear
membrane (with pores), and
chromosomes of linear DNA helix.
Cell wall present ( not of
cellulose)
CELL WALL Cell wall present in plants and fungi
Few organelles; membranous
organelles absent or very
simple
ORGANELLES Many organelles bounded by
double membrane (e.g.
mitochondria, nucleus) or single
membrane (e.g. Golgi apparatus,lysosomes, vacuole, RE)
Proteins synthesised in small
ribosomes
PROTEIN
SYNTHESIS
Proteins synthesised in large
ribosomes
Some cell have simple
flagella, 20nm in diameter
MOTILE
ORGANELLES
Some cells have cilia or flagella with
internal structures, 200 nm in
diameter.
Prokaryotic cells vs. Eukaryotic cells
y Contain nakedDNA vs.DNA associated with proteiny DNA in cytoplasm vs. DNA enclosed in a nuclear envelopey No membrane-enclosed organelles vs. membrane-enclosed organelles (e.g.,
mitochondria, chloroplasts)y 70S vs. 80S ribosomes
2.3.4 State the difference between plant and animal cells
Difference between plant and animal cells
Plant Cells Animal Cells
Cell membrane Cell MembraneCytosol CytosolEndoplasmic reticulum Endoplasmic ReticulumRibosomes RibosomesGolgi Apparatus Golgi Apparatus
Cilia and Flagella Cilia and FlagellaLarger vacuole Smaller vacuole
Chloroplast mitochondria
Cell wall
Chlorophyll
Only plant cells have:
y Cell wallsy Chloroplastsy Large central vacuoles and tonoplasty Plasmodesmatay Starch granules for storage of carbohydrates
Only animal cells have:
y Centriolesy Cholesterol in the plasma membraney Glycogen for storage of carbohydrate
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2.4 embranes
Unit
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1 2fin 2 :
Hydrophilic 3 Having an affinity for water; readily absorbing or dissolving in water.
Hydrophobic 3 Repelling, tending not to combine with, or incapable of dissolving in water.
Hydr4 5
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are notattractedto
waterC butare attractedto each otherA The phosphate headis hydrophilic andthetwo
hydrocarbon tails are hydrophobic. In waterC phospholipidsform doublelayers with the
hydrophilic heads in contactwith wateron both sides andthe hydrophobictails awayfrom
the centre. The attraction between the heads andthe surrounding watermakes membranes
very stable.
2D
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Type Description Examples
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Span the membrane and have a
hydrophiliccytosolic domain, which
interacts with internal molecules, a
hydrophobic membrane-spanning
domain that anchors it within thecell
membrane, and a hydrophilic
extracellular domain that interacts with
IonW
hannQ
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Hydrophilic End
Hydrophobic End
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external molecules. The hydrophobic
domain consists of one, multiple, or a
combination of -helices and sheet
protein motifs.
Lipid anchored
proteins
Covalently-bound to single or multiple
lipid molecules; hydrophobically insert
into the cell membrane and anchor the
protein. The protein itself is not in
contact with the membrane.
Y proteins
Peripheralproteins
Attached to integral membrane proteins,or associated with peripheral regions of
the lipid bilayer. These proteins tend to
have only temporary interactions with
biological membranes, and, once
reacted the molecule, dissociates to
carry on its work in the cytoplasm.
Some enzymes, somehormones
PEECH:
Pumps for active transport.
Enzymes
Electron carriers
Channels for passive transportHormone binding sites.
- Hormone binding sites: Exposed on the outside of the membrane which allows it to bind to
one specific hormone. A signal is transmitted to inside of cell.
- Enzymes: Located in membranes and catalyze reactions inside or outside of cell depending
on its position (inner/outer active site).
- Electron carriers: Arranged in chains in the membrane which allows electrons to pass from
one carrier to another.
- Channels for passive transport:Passages through the centre of membrane proteins that
allows a specific substance to pass through
- Pumps for active transport: Release energy from ATPand use it to move specific substances
across the membrane.
2.4.5 Explain passive transport across membranes in terms of simple diffusion and
facilitated diffusion
Diffusion:
A few substances can diffuse directly through the lipid bilayer part of the membrane. The only
substances that can do this are lipid-soluble molecules such as steroids, or very small
molecules, such as H2O, O2 and CO2. For these molecules the membrane is no barrier at all.
Since lipid diffusion is (obviously) a passive diffusion process, no energy is involved and
substances can only move down their concentration gradient. Lipid diffusion cannot be
controlled by the cell, in the sense of being switched on or off.
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Facilitated Diffusion:
Passive transport is the transport of substances across a membrane by a trans-membrane
protein molecule. The transport proteins tend to be specific for one molecule (a bit like
enzymes), so substances can only cross a membrane if it contains the appropriate protein. As
the name suggests, this is a passive diffusion process, so no energy is involved and substances
can only move down their concentration gradient. There are two kinds of transport protein:
Channel Proteins form a water-filled pore or channel in the membrane. This allows charged
substances (usually ions) to diffuse across membranes. Most channels can be gated (opened
or closed), allowing the cell to control the entry and exit of ions.
Carrier Proteins have a binding site for a specific solute and constantly flip between two states
so that the site is alternately open to opposite sides of the membrane. The substance will bindon the side where it at a high concentration and be released where it is at a low concentration.
Mention channels for facilitated diffusion. A molecule or ion that crosses the membrane by
moving down a concentration or electrochemical gradient and without expenditure of
metabolic energy is said to be transported passively/diffused. All molecules and ions are in
constant motion and it is the energy of motion - kinetic energy - that drives passive
transport. Transport of uncharged species across a membrane is dictated by differences in
concentration of that species across the membrane - that is, by the prevailing concentration
gradient. For ions and charged molecules, the electrical potential across the membrane also
becomes critically important. Together, gradients in concentration and electric potential
across the cell membrane constitute the electrochemical gradient that governs passive
transport mechanisms.Facilitated diffusion is diffusion that is "facilitated" by proteins that span the membrane and
provide an alternative route or bypass. It is similar to simple diffusion in the sense that it
does not require expenditure of metabolic energy and transport is again down an
electrochemical gradient. Two major groups of integral membrane proteins are involved in
facilitated diffusion:
1. Carrier proteins (also known as permeases or transporters) bind a specific type of solute
and are thereby induced to undergo a series of conformational changes which has the effect
of carrying the solute to the other side of the membrane. The carrier then discharges the
solute and, through another conformational change, reorients in the membrane to its
original state. Typically, a given carrier will transport only a small group of related
molecules.
2. Ion Channels do not really bind the solute, but are like hydrophilic pores through themembrane that open and allow certain types of solutes, usually inorganic ions, to pass
through. In general, channels are quite specific for the type of solute they will transport and
transport through channels is quite a bit faster than by carrier proteins. Additionally, many
channels contain a "gate" which is functions to control the channel's permeability. When the
gate is open, the channel transports, and when the gate is closed, the channel is closed. Such
gates can be controlled either by voltage across the membrane (voltage-gated channels) or
have a binding site for a ligand which, when bound, causes the channels to open (ligand-
gated channels). Ion channels allow currents to be carried across the membrane and are thus
of particular importance in the physiology of excitable cells like neurons and muscle cells.
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2.4.6 Explain the role of protein pumps and ATP in active transport across membranes
Active transport is the pumping of substances across a membrane by a trans-membrane
protein pump molecule. The protein binds a molecule of the substance to be transported on
one side of the membrane, changes shape, and releases it on the other side. The proteins are
highly specific, so there is a different protein pump for each molecule to be transported. The
protein pumps are also ATPase enzymes, since they catalyse the splitting ofATP gADP +
phosphate (Pi), and use the energy released to change shape and pump the molecule.
Pumping is therefore an active process, and is the only transport mechanism that can
transport substances up their concentration gradient.
Active transport is the movement of substances across membranes using energy from ATP.
Active transport can move substances against a concentration gradient. Protein pumps inthe membrane are used for active transport. Each pump only transports particular
substances so cells can control what is absorbed and what is expelled.
2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and
reform during Endocytosis and Exocytosis.
The movement of large materials into or out of a cell is called bulk transport. There are
two main categories:
1. Exocytosis2. Endocytosis
Endocytosis:
Endocytosis is the transport of materials into a cell. Materials are enclosed by a fold of the cell
membrane, which then pinches shut to form a closed vesicle. Strictly speaking the material has
not yet crossed the membrane, so it is usually digested and the small product molecules are
absorbed by the methods above. When the materials and the vesicles are small (such as a
protein molecule) the process is known as pinocytosis (cell drinking), and if the materials are
large (such as a white blood cell ingesting a bacterial cell) the process is known as phagocytosis
(cell eating).
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Exocytosis
Exocytosis is the transport of materials out of a cell. It is the exact reverse of endocytosis.
Materials to be exported must first be enclosed in a membrane vesicle, usually from the RER
and Golgi Body. Hormones and digestive enzymes are secreted by exocytosis from the
secretory cells of the intestine and endocrine glands.
In endocytosis part of the plasma membrane is pulled inwards. A droplet of fluid becomes
enclosed when a vesicle is pinched off. Vesicles can then move through the cytoplasm
carrying its contents.
In exocytosis vesicles fuse with the plasma membrane. The contents of the vesicles are then
expelled. The membrane flattens out again.
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2.5 Cell Division
Unit
2.5.1 Outline the stages in the cell cycle, including Interphase (G1,S, G2), mitosis and cytokinesis
Stage Description Illustration
Interphase Chromosomes condense copy
Chromosomes appear as thread like coils
(chromatin) at the start but each chromosomes
and its copy (sister chromosomes) change intosister chromatides at the end of this phase
Interphase
(G1)
Growth and normal metabolic roles
The duplication of organelles
Interphase
(S)
DNA replication- it produces another copy of
each chromosome
Interphase
(G2)
Growth and Preperation for mitosis- second
growth stage
Prophase
(1st phase)
Mitosis begins (cell begins to divide)
Centrioles appear and begin to move to oppositeend of the cell
Spinclole fibres from between the poles
Nuclear membrane begins to dissolve
Metaphase
(2nd
phase)
Chromatids (or pair chromosomes) attach to the
spindle fibres via the centromeres
Anaphase
(3rd phase)
Chromatids separate and begin to move to
opposite ends of the cell
Spindle fibres shorten causing the duplicated
chromosomes to split
Telophase
(4th
phase)
Nuclear membrane begins to reform creating
two new nuclei
Chromosomes appear a chromatin (threads
rather then rods)
In an plant cell and cell plate will form in themidline. This is where the cell wall will be formed
Cytokinesis The division of the cytoplasm enclosing each of
the new cells which become Interphase
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2.5.2 State that tumours (cancers) are the result of uncontrolled cell division and that these can
occur in an organ or tissue
Tumours can be classified as either:
y Terminal/Malignanty Benign
Procedure Explanation
Surgical Removal Aspiration Biopsy: a needle is inserted into the tumour
and a sample is withdrawn.Needle Biopsy: a special cutting needle is inserted into
the core of the tumour and a core sample is cut out.
Incisional Biopsy: a portion of the tumour is removed.
Excisional Biopsy: the whole tumour is removed
w/surrounding normal tissue.
Radiation Therapy Radiation therapy is the use of a certain type of energy
(ionizing radiation) to kill cancer cells and shrink the
tumours. Radiation therapy injures or destroys cell in
the area being treated by damaging their genetic
material, making it impossible for these cells to grow
and divide.
Limits harm to neighbouring healthy tissue.Chemotherapy Chemo for short, means taking certain drugs to treat
cancer. You may take these drugs before or after cancer
surgery or with radiation treatment. Most of chem. Is
given into your veins through a needle or catheter. This
is called venous chemo.
Quite simply, cancer evolves when cells divide uncontrollably and unregulated. The process is
something like;
1. A single cell in a tissue suffers a mutation in a gene involved in the cell cycle, e.g., an
oncogene or tumor suppressor gene.
2. This results in giving that cell a slight growth advantage over other dividing cells in thetissue.
3. As that cell develops into a clone, some if its descendants suffer another mutation in
another cell-cycle gene.
4. This further deregulates the cell cycle of that cell and its descendants.
5. As the rate of mitosis in that clone increases, the chances of further DNA damage increases.
6. Eventually, so many mutations have occurred that the growth of that clone becomes
completely unregulated.
7. The result being full-blown cancer.
Sometimes, mitosis gets out of control and a cell begins to divide and the new daughter cell
begins to divide as well. Soon, this overflow of cells is called a tumor. Tumors can occur in
any organ. Cancer is a disease caused by tumors.
2.5.3 State that Interphase is an active period in the life of a cell when many metabolic reactions
occur, including protein synthesis, DNA replication and mitochondria and chloroplast.
During interphase the cell grows larger. Genes of chromosomes are subsequently
transcribed to allow for protein synthesis. The DNA is then replicated.
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2.5.4 Describe the events that occur in the four phases of mitosis
Prophase (1st
phase)
Mitosis begins (cell begins to divide)
Centrioles appear and begin to move to opposite end of the cell
Spinclole fibres from between the poles
Nuclear membrane begins to dissolve
Metaphase
(2nd phase)
Chromatids (or pair chromosomes) attach to the spindle fibres via the
centromeres
Anaphase(3
rdphase)
Chromatids separate and begin to move to opposite ends of the cellSpindle fibres shorten causing the duplicated chromosomes to split
Telophase
(4th
phase)
Nuclear membrane begins to reform creating two new nuclei
Chromosomes appear a chromatin (threads rather then rods)
In an plant cell and cell plate will form in the midline. This is where the
cell wall will be formed
Include supercoiling of chromosomes, attachment of spindle microtubules, splitting of
centromeres, movement of sister chromosomes to opposite poles and breakage and
reformation of nuclear membranes.
y During Prophase, the mitotic spindle (made from microtubules) starts growing(going from pole to pole).Chromatin coil up to form distinct chromosomes. (Each
chromosome contains two identical sister chromatids, attached to each other at thecentromere region.) The nuclear envelope starts breaks down.
y During Metaphase, each chromosome attaches to two spindle microtubules (onegoing to each pole) at the centromere region, so that they line up at the (virtual)
equator of the cell. The mitotic spindle is fully developed: some microtubules are
attached to chromosomes and reach to the equator, whilst others go from pole to
pole.
y During Anaphase, the spindle microtubules pull the sister chromatids to oppositepoles (each sister chromatid becomes one new chromosome of the daughter cell).
y During Telophase, each sister chromatid reaches its pole (becoming a chromosome).The nuclear envelope starts to reform. Spindle microtubules deteriorate. Cytokinesis
(division of the cytoplasm) takes place.
2.5.5 Explain how mitosis produces the genetically identical nuclei.
The result of the process of mitosis is two nuclei. During S phase, each chromosome
replicates (forms an exact copy of itself). These copies are called sister chromatids. These
identical sister chromatids are separated during Anaphase, and are moved to each pole.
When they are separated they are referred to as chromosomes. The result is two nuclei,
identical to each other and to the original nucleus.
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Extra Info that might be needed
Unit
2.4 Osmosis:
Osmosis is the diffusion of water across a membrane. It is in fact just normal lipid diffusion,
but since water is so important and so abundant in cells (its concentration is about 5 0M),
the diffusion of water has its own name - osmosis. The contents of cells are essentially
solutions of numerous different solutes, and the more concentrated the solution, the moresolute molecules there are in a given volume, so the fewer water molecules there are.
Water molecules can diffuse freely across a membrane, but always down their
concentration gradient, so water therefore diffuses from a dilute to a concentrated
solution.