Download Slides #5A

Cells
Slide 5A.1
BIOM5010
Cellular Organization
© A. Adler, 2011 – 2013
Cells
Slide 5A.2
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Cell Theory
Cells are the smallest units that can live and reproduce on their
own
Discovery
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Microscope manufacturing (van Leeuwenhoek, 1632-1723)
looked at tartar scrapings from his teeth
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Hooke (1635 – 1703) coined the term cell
(like monk's cells: http://dexteroustongue.com/cell/)
Cell Theory
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All organisms are composed of one or more cells
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The cell is the smallest unit of life
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Cells come from previously existing cells
© A. Adler, 2011 – 2013
Cells
Slide 5A.3
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Cell Composition
Cells composed of water and organic
compounds
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Carbohydrates – store energy and structural
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Lipids – oils/fats which don't dissolve in water. Main
store of energy in cells
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Proteins – Diverse class of biomolecules.
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Enzymes for reactions
Structural elements (transport channels across cell wall)
Signals
“chemical weapons” against foreign bacteria
Nucleic acids – Elements of genetic information
© A. Adler, 2011 – 2013
Cells
Slide 5A.4
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Cell structure
Eukaryote (plants, animal cells) – membranes around subcellular structures
Prokaryote (bacterial cells) – only outer plasma membrane
Sizes of cells 10–100 µm (smaller to 1µm for prokaryote)
© A. Adler, 2011 – 2013
Cells
Slide 5A.5
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Cell structure: Membrane
Membrane (cell / plasma membrane).
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to separate and protect a cell
from environment
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made mostly from double layer of
lipids and hydrophilic phosphorus
molecules.
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within this membrane are protein
molecules that act as channels
and pumps that move different
molecules into and out of the cell.
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'semi-permeable', in that it can either let a
substance (molecule or ion)
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contain receptor proteins that allow cells to detect
external signaling molecules such as hormones.
© A. Adler, 2011 – 2013
Cells
Slide 5A.6
Cells in resting state
Cells actively pump ions to maintain electrical charge.
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Sodium pump pumps 3Na+ out for 2K+ in.
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In resting state, membrane permeable to Cl– and K+.
Impermeable to Na+.
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How many Na+ in cell of diameter d=100μm
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Estimate vol = d3 = 10–12m3 =1nL (actual = 0.52×)
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10–9L×(12×10–3mol/L)×(6.023×1023 atoms/mol)
= 7.2240×1018
Concentrations (mM = mmol/L)
Na +
K+
Cl –
120
5
125
3Na + / 2K+
© A. Adler, 2011 – 2013
12
120
5
Cells
Slide 5A.7
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Organelles
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Cell structure: Organelles
As the body contains different organs, each organ performing
a different function. Cells also have a set of "little organs,"
called organelles, specialized for different functions.
There are several types of organelles in a cell.
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nucleus and golgi apparatus: are typically solitary,
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such as mitochondria, peroxisomes and lysosomes) can be
numerous (hundreds to thousands).
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cytosol: gelatinous fluid that fills the cell
© A. Adler, 2011 – 2013
Cells
Slide 5A.8
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Cell Nucleus
Cell nucleus – cell's information center
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houses the cell's chromosomes,
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place where almost all DNA replication and RNA synthesis (transcription) occur.
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spherical and separated from the cytoplasm by a double membrane called the
nuclear envelope, which isolates and protects a cell's DNA
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nucleolus (plural nucleoli) is a non-membrane bound structure composed of
proteins and nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is
transcribed and assembled within the nucleolus.
Genetic material. The biological information contained in an organism is encoded in its
DNA or RNA sequence.
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deoxyribonucleic acid (DNA). Most organisms use DNA for their long-term
information storage
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ribonucleic acid (RNA). used for information transport
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Foreign genetic material can also be artificially introduced into the cell by a
process called transfection. This can be transient, if the DNA is not inserted into
the cell's genome, or stable, if it is.
© A. Adler, 2011 – 2013
Cells
Slide 5A.9
Organelles: Mitochondria
Mitochondria – the power generators
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generate the cell's energy by oxidative phosphorylation, using
oxygen to release energy stored in cellular nutrients (typically
pertaining to glucose) to generate ATP. Respiration occurs in
the cell mitochondria.
Energy + ADP → ATP
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ATP → ADP + Energy
Mitochondria contain their
own genome, which is
separate and distinct from
the nuclear genome
of a cell, …
much like prokaryotic cells
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© A. Adler, 2011 – 2013
Cells
Slide 5A.10
Organelles: Ribosomes
Ribosomes
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large complex of RNA and protein molecules.
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act as an assembly line where RNA from the
nucleus is used to synthesise proteins from amino
acids.
© A. Adler, 2011 – 2013
Cells
Slide 5A.11
Cell Division
General view of cells in
the growing root-tip of
the onion, from a
longitudinal section,
enlarged 800x
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a. non-dividing cells,
with chromatin-network
and deeply stained
nucleoli;
b. nuclei preparing for
division (spiremestage);
c. dividing cells
showing mitotic
figures;
e. pair of daughtercells shortly after
division.
Source: en.wikipedia.org/wiki/Cell_(biology)
© A. Adler, 2011 – 2013
Cells
Slide 5A.12
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Questions
What is the Cell Theory? Why wasn't it obvious
before the microscope?
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What is the function of the cell membrane?
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What is the function of the cell nucleus?
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What is the function of mitochondria?
© A. Adler, 2011 – 2013
Cells
Slide 5A.13
Osmotic Pressure
Osmosis:
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movement of solvent (water) molecules through a selectively
permeable membrane to region of higher solute (ion)
concentration, aiming to equalize the solute (ion)
concentration.
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Net movement of water is from the
less-concentrated
(hypotonic) to the
more-concentrated
(hypertonic). This
effect can be
countered by
increasing the
pressure of the
hypertonic solution
© A. Adler, 2011 – 2013
From: en.wikipedia.org/wiki/Osmosis
Cells
Slide 5A.14
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Hyper- / hypotonic
Suppose a cell is placed in a solution of sugar or salt in water. If
solution is
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hypotonic — higher water concentration than the cell — the
cell will gain water through osmosis.
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isotonic — exactly the same water concentration as the cell
— there will be no net movement of water
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hypertonic — lower water concentration than the cell — the
cell will lose water by osmosis.
Osmolarity = molar concentration of all solutes.
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Osmolarity is distinct from molarity because it measures
moles of solute particles rather than moles of solute. The
distinction arises because some compounds can dissociate
in solution, whereas others cannot.
© A. Adler, 2011 – 2013
Cells
Slide 5A.15
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Osmolarity Example
Cell (volume 1nL) contains 0.2M/L protein. The cell is placed a
large volume of 0.2M/L NaCl. No solute can cross the
membrane.
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Is this hypo- / hyper- / isotonic?
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What happens?
© A. Adler, 2011 – 2013
Cells
Slide 5A.16
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Cell (volume 1nL) contains 0.2M/L protein. The cell is placed a large
volume of 0.2M/L NaCl. No solute can cross the membrane.
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Is this hypo- / hyper- / isotonic? What happens?
Osmolarity inside is 0.2Osm.
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Outside the NaCl dissociates to we have
(0.2 Osm Na+ + 0.2Osm Cl– ) = 0.4 Osm
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Solution is hypertonic relative to cell.
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Water will leave cell, until isotonic = 0.4 Osm
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Osmolarity Example
Particles, P= 0.2mol/L × 1nL = 0.2 nmol (initial volume)
Final volume, V: 0.4Osm = P/V
V = P/(0.4Osm) = 0.2 nmol = 0.5nL
In reality, cells need to match both Osm and electrical charge
© A. Adler, 2011 – 2013
Cells
Slide 5A.17
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Saline Solution
It is important for IV fluid for patients
to be isotonic.
Saline (saline solution): sterile
solution of NaCl in water
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Normal saline (NS) — is the
commonly-used term for a
solution of 0.90% w/v of NaCl,
about 300 mOsm/L or 9.0 g per
liter.
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Also referred to as physiological
saline or isotonic saline, neither of
which is technically accurate.
Source: en.wikipedia.org/wiki/Saline_(medicine)
© A. Adler, 2011 – 2013
Cells
Slide 5A.18
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Questions
Why are some sports drinks “isotonic”?
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As we sweat we loose salt, how does that change
the ionic balance in the body?
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What happens to cells when we drink pure water?
Battlefield medicine often involves dealing with
patients that loose a lot of blood. One new idea
in battlefield medicine is to take small amounts
of very hypertonic saline.
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How does this help?
© A. Adler, 2011 – 2013