Transcript Nerve activates contraction

Cellular Physiology: Membrane Transport
Membrane Transport is the movement of
substance into and out of the cell
Transport is by two basic methods
 Passive transport
 No energy is required
 Active transport
 The cell must provide metabolic energy
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Solutions and Transport
Solution – homogeneous mixture of two or
more components
 Solvent – dissolving medium (liquid)
 Solutes – components in smaller quantities
within a solution (“stuff”)
Intracellular fluid - fluid inside the cell
 nucleoplasm and cytosol
Interstitial fluid – fluid on the exterior of the
cell, between cells
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Tonicity - is the degree to which a solution’s
concentration of solute versus water (solvent) causes
water to move into or out of a cell
Solute
Solvent
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Selective Permeability
Membranes are selectively permeable
 The plasma membrane allows some materials
to pass while excluding others
 This permeability includes movement into
and out of the cell
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Passive Transport Processes
Diffusion Does NOT require ATP
 Particles tend to distribute themselves evenly
within a solution
 Movement is
from high
concentration
to low
concentration,
or down a
concentration
gradient
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Figure 3.9
Passive Transport Processes
Types of diffusion
1.
Simple diffusion
2. Osmosis
3.
Facilitated diffusion
1. Simple diffusion

Unassisted process

No ATP required

Solutes are lipid-soluble materials or small enough
to pass through membrane pores
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Passive Transport Processes
Types of diffusion
2. Osmosis – simple diffusion of water
 Highly polar water crosses the plasma
membrane through aquaporins
3. Facilitated diffusion
 Substances require a protein carrier for passive
transport
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Diffusion through the Plasma Membrane
Flows from High Concentration
to a Low concentration
Figure 3.10
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Active Transport Processes
Active Transport requires ATP
Transport substances that are unable to pass by
diffusion
 They may be too large
 They may not be able to dissolve in the fat core
of the membrane
 They may have to move against a concentration
gradient
Two common forms of active transport
 Solute pumping
 Bulk transport
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Active Transport Processes
Solute pumping
 Amino acids, some sugars and ions are
transported by solute pumps
 ATP energizes protein carriers, and in
most cases, moves substances against
concentration gradients
Videopump
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Active Transport Processes
Sodium Potassium Pump
Figure 3.11
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Review Slide – DO NOW
1. How is passive transport different from active
transport?
2. If I make Iced Tea from a sugary powdered mix and
water, which is the solvent and which is solute?
3. Where would you find interstitial fluid in your body?
4. What does selectively permeable mean?
5. What is the main difference between simple diffusion
and facilitated diffusion
6. Why is solute pumping considered a form of active
transport?
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Active Transport Processes
Bulk transport
Exocytosis - Moves materials out of the cell
 Material is carried in a membranous vesicle
 Vesicle migrates to plasma membrane
 Vesicle combines with plasma membrane
 Material is emptied to the outside
 Requires ATP
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Exocytosis
Figure 3.12a
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Active Transport Processes
Bulk transport
Endocytosis - Substances into the cell
 Extracellular substances are engulfed by
being enclosed in a membranous vescicle
 Types of endocytosis
 Phagocytosis – cell eating
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 Pinocytosis – cell drinking
Pinocytosis and Phagocytosis
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Endocytosis
Figure 3.13a
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Review Slide
 What is the difference between a solute and a
solvent?
 How is Passive transport different from
Active transport?
 Intracellular fluid vs. Interstitial Fluid?
 List and Describe the Types of Passive
transport - Give an example of each
 Compare and contrast endocytosis and
exocytosis
Why do cells
need to divide?
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Where does
mitosis occur in
your body?
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Cell Life Cycle
Cells have two major periods to its Life cycle
 Interphase
how_the_cell_cycle_works.html
 Cell grows
 Cell carries on metabolic processes
 Cell division (Mitosis)
 Cell replicates itself
 Function is to produce more cells for growth
and repair processes
 Mitosis: An Interactive Animation
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Animation: Mitosis and Cytokinesis
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Cell Cycle
Living cells go through a series of stages known as the cell cycle.
The cells grow, copy their chromosomes, and then divide to form
new cells.
 G1 phase. The cell grows.
 S phase. The cell makes copies of its chromosomes. Each
chromosome now consists of two sister chromatids
 G2 phase. The cell checks the duplicated chromosomes
and gets ready to divide.
 M phase. The cell separates the copied chromosomes to
form two full sets (mitosis) and the cell divides into two
new cells (cytokinesis).
 The period between cell divisions is known as ‘Interphase'.
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m
 Mitosis is used to produce daughter
cells that are genetically identical to the
parent cells. mitosis_and_cytokinesis.ht
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 Meiosis is used to make special cells sperm cells and egg cells - that have half the
normal number of chromosomes. It reduces
the number from 23 pairs of chromosomes to
23 single chromosomes.
 Meiosis
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DNA Replication to prepare for Mitosis
 DNA is duplicated to
prepare the cell for
division
 Occurs toward the
end of interphase
during the “S phase”
 DNA uncoils and
each side serves
as a template
Figure 3.14
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Part I - Mitosis
 Division of the nucleus
 Results in the formation of two daughter
nuclei
Part II - Cytokinesis
 Division of the cytoplasm
 Results in the formation of two identical
daughter cells
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Stages of Mitosis
Stages of Mitosis
Interphase – Has phases – G1, S G2
 No cell division occurs
 The cell carries out normal metabolic
activity and growth and prepares for
division
Prophase
 First part of cell division
 Centrioles migrate to the poles
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Stages of Mitosis
Metaphase
 Spindle from centrioles are attached to
chromosomes that are aligned in the
center of the cell
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Stages of Mitosis
Anaphase
 Daughter chromosomes
are pulled toward the poles
 The cell begins to elongate
Telophase
 Daughter nuclei begin
forming
 A cleavage furrow (for cell
division) begins to form
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Stages of Mitosis
Figure 3.15
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Stages of Mitosis
Figure 3.15(cont)
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Mitosis Lab
 Mitosis in Plant Cells
 Objective: to observe the stages of mitosis in plant
cells
Materials: onion root tip slide
 Procedure:
 1. Observe the onion root tip in low power and high
power.
 2. Locate four cells in four different stages of
mitosis
 3. Draw and label each of the four stages in high
power
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Conclusion:
 1. Describe how you recognized a cell in prophase.
 2. Where are the chromosomes located in metaphase?
 3. What is happening in anaphase?
 4. Describe how the 2 daughter cells compare to the parent cell.
 5. Describe how the 2 daughter cells compare to EACH OTHER.
 6. What is mitosis?
 7. What kind of cells go through mitosis? Give two examples
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Prophase? Metaphase? Anaphase? Telophase?
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Prophase? Metaphase? Anaphase? Telophase?
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Prophase? Metaphase? Anaphase? Telophase?
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