chapter 8. the boundary between the cell and its environment controls what enters and exits the...
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Cell Transport and the Cell Cycle
Chapter 8
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Plasma Membrane
The boundary between the cell and its environment
Controls what enters and exits the cell (selective permeability)
- nutrients, wastes, water
Maintain homeostasis
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Plasma Membrane
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Diffusion
Movement of particles from high low concentration
Happens because of the random movement of particles
Three things affect the rate of diffusion:- concentration (how much),
temperature, and pressure
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Diffusion
Diffusion results in an evenly distributed solution
- when this happens its called dynamic
equilibrium
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OsmosisOsmosis is the diffusion of water.
From high low concentration
In a cell, water always tries to reach an equal concentration on both sides of the membrane.
Important in maintaining homeostasis
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How Osmosis Affects Cells
Hypotonic Solution:- more water outside the cell
than inside- water moves into the cell- cell swells
Hypertonic Solution:- more water inside the cell than
outside- water moves out of the cell- cell shrinks
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How Osmosis Affects Cells
Isotonic Solution:- amount of water is the same
outside and inside the cell- cell stays the same
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Passive Transport (Diffusion, Osmosis, Facilitated Diffusion)
Movement of particles across membranes by diffusion
High low concentration
Requires no energy
Passive transport with the help of transport proteins is called facilitated diffusion
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Active Transport
Movement of materials through a membrane against a concentration gradient.
Low high concentration
Energy required
Uses carrier proteins
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Active Transport
Transport of large particles:endocytosis – cell surrounds and
takes in material from its
environmentexocytosis – expulsion or
excretion of materials from a cell
(wastes, indigestible
particles)
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What Limits Cell Size?
Diffusion limits cell size!!- short distances = fast and efficient diffusion- long distances = slow and inefficient
diffusion
DNA limits cell size
Surface area-to-volume ratio- as a cell size increases, its volume
increases faster than its surface area - what does this mean for the cell?
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Cell Growth and Reproduction
Chapter 8.2
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Cell Reproduction
Remember the cell theory states that all cells come from preexisting cells.
Cell division is the process by which new cells are produced from one cell.
We lose cells constantly throughout the day and they are constantly being replaced.
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What are Chromosomes?
Carriers of the genetic material (DNA) that is copied and passed from generation to generation.
Located in the nucleus
Exist as chromatin (uncoiled) for most of its life.
Before cell division, the chromatin (DNA) coils up tightly and is called chromosomes
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Chromosome Structure
1. Chromatid2. Centromere3. Short arm4. Long arm
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The Cell Cycle
The sequence of growth and division of a cell.
Cells go through two general periods:- growth period (interphase)- division period (mitosis)
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Interphase (Growth)
The majority of a cells life is spent here
G1 phase – cell growth S phase – DNA is copied G2 phase – growth and getting ready for
cell division
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Mitosis (Division)
Starts with one cell and results in two identical cells (daughter cells)
Four phases of mitosis:1. Prophase (longest phase)
- chromosomes coil up and double- nuclear envelope and nucleolus break down and disappear- spindle fibers form- centrioles migrate to opposite
poles
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Mitosis (Division)
2. Metaphase:- chromosomes line-up in
middle- spindle fibers attach to
centromeres of chromosomes
3. Anaphase:- chromosomes separate
and move to opposite poles
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Mitosis (Division)
4. Telophase:- chromosomes uncoil (back
into chromatin)- spindle fibers breakdown- nucleolus and nuclear
envelope reappear
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Cytokinesis
Division of the cytoplasm
In animal cells, plasma membrane pinches in and forms a cleavage furrow.
In plant cells, a rigid cell plate is formed across the equator of the cell.
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Cellular Organization
Cell tissue organs organ system organism
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Cancer
Enzymes control the cell cycle
If the cell cycle gets out of control, then cells divide without stopping.
Cancerous cells form masses called tumors