Download Chapter 4 The Cell: The Fundamental Unit of Life

5/12/2015
Cell Makeup
Chapter 4
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We previously talked about the cell membrane
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The cytoplasm is everything inside the
membrane, except the nucleus
The Cell:
The Fundamental Unit of Life
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Includes…
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Cytosol = liquid portion
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Organelles (NOTE ERROR IN STUDY GUIDE)
Lecture 3: Organelles
Cell Size
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Cell Size
Glucose is 108 times smaller than a bacterium
Cells are small, but molecules for their chemical
reactions are much smaller
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Reactants needed for metabolism are present in
low concentrations
Utah Genetics
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Low concentration means reactants don’t collide
often
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(Don’t draw this
in your study guide)
Cell Size
Cell Size
Concentration gets lower as cells get bigger
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Why prokaryotic cells stay small
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What happens to chemical reaction rate in cells
as cells get bigger?
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Eukaryotic cells have found a way around this:
membrane--bound organelles
membrane
(Draw this one
in your study guide)
Relative Rate of Reaction
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Serve to concentrate reactants in appropriate
compartments
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Improve cell efficiency
Cell Size
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Cell Size
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Cell Size
This means eukaryotic cells can be larger than
prokaryotic cells
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Still, being small has some advantages
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Solutes taken into cells through membrane
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Consider 2 cubes (even though most cells are
spherical)…
2 µm
1 µm
Cell Size
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Volume increases faster than surface area
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Organelles
(x3
vs
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Often categorized by presence/absence of
membrane(s)
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Non--membranous
Non
x2)
So as cells get bigger, the proportion of surface
area decreases
Keeps cells small
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Cells need surface area to absorb solutes
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Less surface area = fewer reactions
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Mitochondria
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Cellular extensions
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Endoplasmic
reticulum
Organelles
We will consider the organelles’ contribution to
the production and management of protein
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Non--membranous
Non
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Membranous
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Cytoskeleton
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Cellular extensions
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Mitochondria
Membranous
Cytoskeleton
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Microvilli
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Cilia
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Golgi aparatus
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Flagella
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Lysosomes
Ribosomes
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Peroxisomes
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Nucleus
Ribosomes
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Site of protein synthesis
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Abundant in cells that produce a lot of protein
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Example: human liver cells have on average
13 million ribosomes in each cell!
Endoplasmic
reticulum
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Microvilli
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Cilia
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Golgi aparatus
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Flagella
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Lysosomes
Ribosomes
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Peroxisomes
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Nucleus
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Ribosomes
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Made from rRNA (2 units)
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Polypeptide chain constructed using information
provided by mRNA
Ribosomes
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Many ribosomes can read the same strand of
mRNA at once
mRNA
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Contains information for…
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Amino acid sequence
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Final destination of protein
mRNA
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Final destination of protein
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Bound for cytosol
cytosol,, = binds to free ribosome
mRNA
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Final destination of protein
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Bound for export, membrane, or membranemembranebound organelle = mRNA/ribosome complex
associates with endoplasmic reticulum
Endoplasmic Reticulum
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Collection of membranous tubes and envelopes
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2 forms
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Smooth endoplasmic reticulum (sER
(sER))
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Site of lipid synthesis, detoxification
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Abundant in liver, kidney, endocrine glands
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Rough Endoplasmic Reticulum
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Rough Endoplasmic Reticulum
Proteins enter rER
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Some vesicles stay in cytoplasm
through pore
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Others migrate to the Golgi apparatus
Portion of rER pinches
off to encapsulate
protein in a transport
vesicle
Golgi Apparatus
Golgi Apparatus
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Cis face =
Receiving face
Transport vesicle
Proteins are modified and/or combined in the
Golgi, encapsulated and transported to…
1.
Secretory vesicles
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Trans face =
Shipping face
Vesicles bound
for elsewhere
Golgi Apparatus
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Proteins are modified and/or combined in the
Golgi, encapsulated and transported to…
2. Cell membrane components
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Example: glycoproteins
Proteins for discharge from cell
Golgi Apparatus
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Proteins are modified and/or combined in the
Golgi, encapsulated and transported to…
3. Lysosomes
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Cytosolically--active vesicles
Cytosolically
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Lysosomes
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Contain more than 50 enzymes
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pH of ~4.5
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Break down almost any biomolecule
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Cell’s “garbage disposal”
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Can fuse with other membranemembrane-defined
structures and release contents
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Lysosome storage diseases (>30)
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Example: TayTay-Sachs disease
Peroxisomes
Mitochondria
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Originate in rER
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Site of ATP synthesis – “powerhouse of cell”
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Involved in lipid catabolism, modification
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Features:
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Produce oxidative enzymes, hydrogen peroxide
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Double membrane (inner and outer)
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Detoxifies substances in kidney by means of
peroxidation
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Carry own DNA, make some of their own
protein
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Only cellular site to use molecular oxygen
Mitochondria
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Provide energy = most abundant in cells that
need a lot of energy
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Examples: muscle cells, sperm
Cytoskeleton
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Internal protein network of cells
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Stabilize cell’s 33-dimensional shape
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Guide vesicles
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Microtubules
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Microtubules
Formed from tubulin subunits
2. Intracellular transport with motor proteins
1. Component of cytoskeleton – cell shape,
anchor organelles
Microtubules
Microtubules
3. Move chromosomes during cell division
4. Cilia, flagella
Intermediate Filaments
Microfilaments
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>60 different kinds
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Made of actin subunits
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Resist stretching
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Functions:
Associated with cell movement, changes in cell
shape
1. Strength
2. Stabilize
organelle
position
3. Transport
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Comparison of Cytoskeletal Proteins
Thick Filaments
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~15nm diameter
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Example: myosin in muscle
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Interacts with actin for movement
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Microfilaments = 33-6nm in diameter
Cellular Extensions
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Cilia
Cellular Extensions
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Flagella
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Whip--like
Whip
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Substantially longer than cilia
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Move substances in one direction across
stationary cells
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Only example in human body: sperm
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Example: trachea
Cellular Extensions
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Microvilli
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Very small, highly numerous
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Increase absorptive surface area
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Example: small intestine
Nucleus
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Genetic library
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Contains all instructions needed to build cell’s
proteins
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Dictates types, amounts of proteins to be made
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Responds to extracellular signals
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