Cells

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Cells

• Cytology

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I. The Cell Theory 2.1.1

• Made up of three parts
• All living things are made up of cells
• Cells come from other cells
• Cells are the basic unit of structure of all
  living things

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THE CELL THEORY 2.1.2

• Evidence to support the cell theory
• Robert Hooke first views cells in cork (1665)
• Anton von Leeuwenhoek views living cells in algae
  (1674)
• Schwann and Schleiden study plants and come up
  with the theory (1838)
• Improved microscopes have allowed for a more
  exact study of living things, and no organism has
  been discovered that is not made of cells

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• Arguable EXCEPTIONS to the Cell Theory
• Some tissue has extracellular material (like
  tooth dentine), and the cells make up only a tiny
  percentage of the total tissue volume
• Skeletal muscle cells contain hundreds of
  nuclei each (and can be 30 cm in length)
• Hyphae cells in fungus are continuous due to
  septa, and have many nuclei
• Viruses are non-cellular (and thus debatably
  non-living
• Consist of only DNA or RNA surrounded by a
  protein coat

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• Unicellular organisms are unique (and argued by
  some to be acellular) because they carry out
  all the Functions of Life within a single
  cytoplasm (2.1.3)

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Functions Of Life

1. Metabolism chemical reactions necessary for
   life
2. Response
3. Homeostasis maintenance of internal stability
   (equilibrium)
4. Growth
5. Reproduction
6. Nutrition

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Stem Cells (2.1.9 2.1.10)

• Stem Cells are unique cells that are
  undifferentiated, meaning that they dont yet
  have an identity, or function.
• Depending on the type of stem cell, they may be
  induced to become any particular type of cell.
• Due to the work of Christopher Reeve, stem cells
  are now being use to regrow neural tissue (in
  mice.)

• There are between 10 and 100 trillion cells in a
  human body. There are also approx half as many
  bacteria in there as well. Each cell has
  30,000 genes, and about 3 billion nucleotide
  pairs. There are 100 billion neurons in the
  brain, and about 25 times as many support cells
  (glia.)

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1 mm 1 x 10-3 meters 1 millimeter 1 µm 1
x 10-6 meters 1 micrometer 1 nm 1 x 10-9
meters 1 nanometer
Every step to the left represents an increase of
10X
1 mm 10 µm 100 nm
1 nm
(1 angstrom)
10 mm 100 µm 1 µm
10 nm 0.1 nm
The size of a molecule (DNA 2nm)
Resolution of human eye
Size of a virus
Eukaryotic cells
Thickness of a cell membrane
Average bacteria
2.1.5
Size of organelles (varies)
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II. Importance of Surface Area to Volume ratio
in determining cell size (2.1.6)

• Cells can not keep growing they reach a maximum
  size and then divide

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As the cell gets larger, the surface area to
volume ratio gets SMALLER
For a cube

• Sides S.A. Vol Ratio
• 1 cm
• 2 cm
• 3 cm
• 4 cm
• 5 cm

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As the cell gets larger, the surface area to
volume ratio gets SMALLER
For a cube

• Sides S.A. Vol Ratio
• 1 cm 6 cm2
• 2 cm 24 cm2
• 3 cm 54 cm2
• 4 cm 96 cm2
• 5 cm 150 cm2

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As the cell gets larger, the surface area to
volume ratio gets SMALLER
For a cube

• Sides S.A. Vol Ratio
• 1 cm 6 cm2 1 cm3
• 2 cm 24 cm2 8 cm3
• 3 cm 54 cm2 27 cm3
• 4 cm 96 cm2 64 cm3
• 5 cm 150 cm2 125 cm3

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As the cell gets LARGER, the surface area to
volume ratio gets SMALLER
For a cube

• Sides S.A. Vol Ratio
• 1 cm 6 cm2 1 cm3 6
• 2 cm 24 cm2 8 cm3 3
• 3 cm 54 cm2 27 cm3 2
• 4 cm 96 cm2 64 cm3 1.5
• 5 cm 150 cm2 125 cm3 1.2

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cell size, contd

• The rate that things can enter and leave a cell
  depend on the surface area
• The metabolic rate depends on volume
• Cells that get too large cant take in essential
  materials (food!) or excrete wastes quickly
  enough
• The same principle holds true for
  heat cells must be able to
  release it

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Small cells are the most efficient, because they
can easily transport materials throughout the
cell
Example Potato cubes (starch) in Iodine
1) 4 cm
2) 2 cm
3) 1 cm
All blue/black
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III. Prokaryotic vs. Eukaryotic Before
Nucleus True Nucleus
p5 in IBRB 2.2.1

• A. Prokaryotic Cell bacteria

Mesosome
Ribosome
Plasmid (DNA)
Plasma Mem- brane
cytoplasm
Cell Wall
Slime Capsule
Ring-shaped chromosome (DNA) Naked DNA (only
loosely associated with proteins)
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2.
1.
4.
3.
Basal Body
10.
5.
6.
8.
7.
9.
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...diagram explanation 2.2.2
Make sure you can label these things in an E.
coli micrograph use the IBRB! 2.2.3

• Ribosome protein synthesis 70s
• Mesosome (extra) increases the surface area of
  the plasma membrane for more ATP production
  might move naked DNA to different ends of the
  cell during bacterial cell division (called
  binary fission)
• Slime Capsule protection adhesion (tooth
  plaque)
• Flagellum movement

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• Cell Wall protects from bursting or shrinking
• Plasma Membrane controls passage of material in
  and out of cells
• Naked DNA (nucleoid) stores genetic information
  located in an area of the cell called the
  nucleoid DNA not associated with histone
  proteins like eukaryotic DNA (thus naked)
• Cytoplasm contains enzymes to catalyze
  reactions important for metabolism
• Pili- used for adhering to surfaces as well as
  joining to other bacteria in order to conjugate-
  that means SEX!!

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Multi-cellular organisms vs. Unicellular organisms

• Multicellular organisms All cells have the same
  DNA but differentiated cells carry out
  specialized functions by expressing some of their
  genes but not others 2.1.8
• cell differentiation when cells become
  specialized in structure and function
• Unicellular organisms carry out all of the
  functions of life within a single cell 2.1.3

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• Multicellular organisms show emergent
  properties (2.1.7)
• When a number of simple entities (in this case
  cells) come together to form a more complex
  collective

The heart is a single organ that comes together
to form the cardiovascular system (an ORGAN
SYSTEM)
Cardiac tissue comes together to form the heart
(an ORGAN)
Cardiac muscle cells form this cardiac TISSUE
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B. Eukaryotic Cells
Make sure you can label and annotate a diagram!
2.3.1, 2.3.2,2.3.3

• Nucleus stores genetic material in chromatin
  (DNA mixed with proteins) during cell division
  the chromatin clumps into chromosomes membrane
  bound
• Ribosomes (free and rough) make proteins,
  ribosomes have no membranes 80s
• In the cytoplasm or on the ER depending on what
  sort of proteins they produce (for the cell or to
  be secreted)
• Endoplasmic reticulum network of
  interconnecting tubes continuous with the
  nuclear membrane detoxifies molecules, produces
  lipids, metabolizes carbs, makes membranes

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• Golgi body (apparatus) accepts vesicles from
  the ER that contain proteins needing to be
  processed and exported from the cell (as
  glycoproteins, lipoproteins glycolipids)
• cis end nearest to the nucleus and the ER
• trans face nearest to the cell membrane
• Vesicles membrane-bound packages in the cell
  used to transport molecules around safely
• Mitochondria enclosed in an envelope of two
  phospholipid bilayers site of cellular
  respiration (making ATP through catabolism)
• Lysosomes contains hydrolytic digestive enzymes
  to break the 4 major biological molecules down
  (so their parts can be used elsewhere)

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• Using all of the eukaryotic organelles, explain
  their functions as they work together to produce
  some cellular product.

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C. Prokaryotic vs. Eukaryotic

• See p. 6 in IBRB
• (differ in type of DNA, location of DNA, presence
  of mitochondria for ATP synthesis, size of
  ribosomes (.70S vs .80S), and membrane-bound
  organelles) 2.3.4
• See p. 6 in IBRB
• (differ in presence of cell wall, chloroplasts,
  and vacuole, type of carbohydrate used for
  storage, and shape) 2.3.5

D. Plant vs. Animal Cell
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E. Extracellular components the plant cell wall
2.3.6 (wall protects, maintains shape, and
prevents excessive water uptake)
Microfibrils (bundles) of Cellulose
Pectin
(DON T WRITE) Pectin is an adhesive which helps
to hold plant cells together (it is added to jam
as a thickener, and removed from fruit juice with
pectinase to keep it from solidifying)
Cell wall is 10X-100X thicker than plasma membrane
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Animal cell extracellular component glycoproteins

• These carbohydrate-protein molecules aid in
  support, adhesion (for cell-to-cell connection),
  and movement

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IV. Movement in and out of cells 2.4.4

• A. Diffusion random movement of molecules from
  a high concentration to a low concentration

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B. Osmosis- movement of water across a
semi-permeable membrane from a low solute to a
high solute concentration 2.4.4
Osmotic pressure is the pressure that water puts
on something when it wants to cross a membrane
10 sucrose 90 water bag is hypertonic 1
sucrose 99 water water is hypotonic
Bag will GAIN water.
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Molecules will always diffuse with respect to
their own concentration gradient
DONT WRITE
Here, water wants to move left, down its
concentration gradient. Red circles want to move
right, down their concentration gradient.
Here, water wants to move left, down its
concentration gradient Green circles want to
move left, down their concentration
gradient. Purple circles want to move right,
down their concentration gradient.
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DONT WRITE
This membrane is permeable to H2O, but not to the
sugar molecules floating in it what will happen?
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DONT WRITE
water will diffuse until the two sides are
isotonic (in equilibrium)
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• Isotonic both solutions have the same
  concentration of solute

Potato 0.5 M glucose
0.5 M Solution of glucose
There is NO net movement of glucose or water
(equilibrium)
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• Solutions can be compared to others using two
  RELATIVE terms
• Hypertonic higher solute concentration
• Hypotonic lower solute concentration
• Water will always try to move towards the
  HYPERTONIC solution

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Practice
DONT WRITE
1 salt 99 water

• Q Cell will shrink or swell?
• A Shrink, because the solution is hypertonic!

5 salt 95 water
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examples

• In animal cells blood cells
• In plants

RBC
In hypotonic solution water goes
in In hypertonic solution, In hypotonic
solution water goes in In hypertonic
solution, water leaves -could have
plasmolysis!
CELL BURSTS LYSIS! Cell
wrinkles Turgid Wilted
RBC
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The phospholipid bilayer has fluidity, which
allows it to change shape
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• the hydrophobic and hyrophilic properties of
  each phospholipid help to maintain the bilayers
  structure 2.4.1, 2.4.2

Hydrophilic portion of the phospholipid will
remain exposed to the water
Hydrophobic portion will stay away from the
water, towards the middle
Cholesterol molecules are also embedded along
with hydrophobic tails (for structure)
INTEGRAL PROTEIN PERIPHERAL PROTEIN
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Functions of membrane proteins 2.4.3

• Hormone binding sites transmit a signal when a
  hormone is present
• Enzymes
• Electron carriers pass electrons along
• Channels for passive transport allow a single
  substance to pass
• Passive tranport no energy necessary
• Pumps for active transport use ATP (ATP ? ADP
  P) as energy to push things through (oftentimes
  against their gradient)
• p7 in IBRB

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2.4.5 and 2.4.6

• FACILITATED DIFFUSION (IBRB p8) passive
  diffusion through a channel protein
• ACTIVE TRANSPORT (IBRB p8) unlike facilitated
  diffusion, it can be used to move substances into
  or out of the cell AGAINST their concentration
  gradient (this takes ATP energy and can be done
  through by protein pumps)

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• Phospholipid-bound bubbles called vesicles are
  used to transport materials within the cell
  (2.4.6)
• ENDOCYTOSIS bringing things into the cell via
  vesicles
• EXOCYTOSIS secreting things out of the cell via
  vesicles

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• In exocytosis (2.4.7, 2.4.8)
• Vesicles transport materials
• Rough ER ? Golgi ? membrane