chapter3-part1
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Copyright 2010, John Wiley & Sons, Inc.
Chapter 3
Cells
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Copyright 2010, John Wiley & Sons, Inc.
Cell Structure
� Plasma membrane
� Cytoplasm: cytosol + organelles
� Nucleus
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Generalized View of Cell Structure
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Cell Membrane
� Phospholipid bilayer
� Cholesterol
� Proteins (integral and peripheral)� Attached carbohydrates (glycolipids and
gycoproteins)
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Copyright 2010, John Wiley & Sons, Inc.
Plasma Membrane: Chemistry and
Structure
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Membrane Function
� Barrier between inside and outside of cell
� Controls entry of materials: transport
� Receives chemical and mechanical signals
� Transmits signals between intra- and extra-
cellular spaces
� Note variety of proteins in Figure 3-2.
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Terminology: Body Fluid Pools
� Intracellular (ICF)
± Within cells: 2/3 of total
� Extracellular (ECF):
± Between cells = Interstitial
± In blood vessels = Plasma
± In lymphatic vessels = Lymphatic
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Terminology: Solutions
� Solvent: the liquid doing the dissolving ± Usually water
� Solute: the dissolved material (particles orgas)
� Concentration ± Amount of solute in a given amount of solvent
� Concentration gradient ±
Difference in concentration between 2 areas of solution
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Principle of Diffusion
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Passive Transport: Simple Diffusion
� Requirements for simple diffusion ± Concentration gradient of solute present
± Solute can diffuse across a membrane if membrane is present
� Pathways of simple diffusion:
± Pass across lipid bilayer if lipid-soluble (O2, CO2,N2, fatty acids, steroids, fat-soluble vitamins), or if polar molecules (H2O, urea)
± Pass through ion channels (which may be gated:gates open and close) if ions such as K+, Ca2+, Cl
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Simple Diffusion
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Facilitated Diffusion� Requires a carrier in membrane but not ATP
� Solute goes down concentration gradient
� Maximum transport speed depends on
number of carriers ± insulin increases number of carriers for glucose in
plasma membrane
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Facilitated Diffusion
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Facilitated Diffusion
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Osmosis�
Diffusion of water across selectivelypermeable membrane:
± Permeable to solvent
± Impermeable to solute
� Types of solutions surrounding human RBCs
± Isotonic: solution outside RBC has same
concentration of solute as RBC: 0.9% NaCl
± Hypotonic: solution outside of RBC has lowerconcentration: 0% NaCl hemolysis
± Hypertonic: solution outside of RBC has higher
concentration: 4% NaCl crenation
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Osmosis
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Osmosis
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Active Transport� Requires a carrier (called a pump)
� Requires energy (ATP)
� Can transport up a concentration gradient
� Critical for moving important ions
� Major active transport in most cells is sodium-
potassium (Na+/K+) pump
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Active TransportSolutes are transported across plasma membranes with the use of energy,from an area of lower concentration to an area of higher concentration
Example: Sodium-potassium pump
1
3 Na+
K+
gradient
Cytosol
1
3 Na+ expelled
3 Na+
ADPP
P
2 K+
imported
K+
gradient
Na+
gradientNa+/K+ ATPase
Extracellular fluid
Cytosol
2K+
ATP2 3 4
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Transport in Vesicles
� Requires energy (ATP)
� Involves small membrane sac
� Endocytosis: importing materials into cell
± Phagocytosis: ingestion of particles such as
bacteria into white blood cells (WBCs)
± Pinocytosis: ingestion of fluid
� Exocytosis: exporting materials
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� Transport Across the Plasma Membrane
Transport Across the Plasma
Membrane
Interactions Animation
You must be connected to the internet to run this animation.
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Cell Organelles: Table 3.2
� Cytoskeleton
� Flagella, cilia & centrioles
� Endoplasmic reticulum
� Golgi apparatus
� Mitochondrion
� Nucleus, nucleolus, nuclear envelope
� Vesicles, e.g. lysosome
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Cytoplasm
� Cell contents
� Includes organelles and cytosol
� Excludes nucleus
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Cytoskeleton
� Maintains shape of
cell
� Positions organelles
� Changes cell shape
� Includes:
microfilments,
intermediate
filaments,
microtubules
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Centrosome
� Structure:
± Two centrioles arranged perpendicular to each
other
� Composed of microtubules: 9 clusters of 3 (triplets)
± Pericentriolar material
� Composed of tubulin that grows the mitotic spindle
�
Function: moves chromosomes to ends of cellduring cell division
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Centrosome
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Cilia and Flagella
� Specialized for motion
� Flagellum: single tail like structure on sperm
± Propels sperm forward in reproductive tract
� Cilia: in groups
± Found in respiratory system: move mucus
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Ribosomes
� Made within the nucleus (in nucleolus)
� Sites of protein synthesis (on E.R. or freely
within cytoplasm)
� Consist of ribosomal RNA (rRNA) + proteins
� Contain large and small subunits
� Can be attached to endoplasmic reticulum or
free in cytosol
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Endoplasmic Reticulum (E.R.)�
Structure: network of folded membranes� Functions: synthesis, intracellular transport
� Types of E.R.
±Rough E.R.: studded with ribosomes (sites of protein synthesis)
± Smooth E.R. lacks ribosomes. Functions:
� lipid synthesis
� release of glucose in liver cells into bloodstream
� drug detoxification (especially in liver cells)
� storage and release of Ca2+ in muscle cells (where
smooth E.R. is known as sarcoplasmic reticulum or SR)
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Endoplasmic Reticulum (E.R.)
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� Structure:
± Flattened membranes (cisterns) with bulging
edges (like stacks of pita bread)
� Functions:
± Modify proteins glycoproteins and
lipoproteins that:
�
Become parts of plasma membranes� Are stored in lysosomes, or
� Are exported by exocytosis
Golgi Complex
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Golgi Complex
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Small Bodies� Lysosomes: contain digestive enzymes
± Help in final processes of digestion within cells
± Carry out autophagy (destruction of worn out parts of
cell) and death of old cells (autolysis)
± Tay-Sachs: hereditary disorder; one missing lysosomal
enzyme leads to nerve destruction
� Peroxisomes: detoxify; abundant in liver
� Proteasomes: digest unneeded or faulty proteins
±Faulty proteins accumulate in brain cells in persons withParkinson or Alzheimer disease.
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Mitochondria
� Structure:
± Sausage-shaped with many folded membranes
(cristae) and liquid matrix containing enzymes
±
Have some DNA, ribosomes (can make proteins)� Function:
± Nutrient energy is released and trapped in ATP; so
known as power houses of cell
± Chemical reactions require oxygen
� Abundant in muscle, liver, and kidney cells
± These cells require much ATP
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