CELL TRANSPORT
AND
THE CELL CYCLE
CELL TRANSPORT
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DIFFUSION:
•
movement of material from higher concentration to lower
concentration
•
OSMOSIS:
Diffusion of water
•
FACILITATED
DIFFUSION
•
Molecules
transport across a membrane in the direction of lowest concentration by a
carrier protein; no energy required
•
ACTIVE TRANSPORT:
•
Movement
of large material against a concentration difference requiring energy to be
used. (Ca, K, Na pumps)
Different States of Diffusion
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Isotonic
solution: concentration of dissolved substances in the solution is the same as
the concentration of dissolved substances inside the cell
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Hypotonic
solution: lower outside the cell than inside; more water outside – water moves
in
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Hypertonic
solution: higher outside the cell than inside; more water inside – water moves
out
CELL TRANSPORT
CONT.
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PERMEABILITY:
•
Ability of a
membrane to diffuse material
•
depends on concentration differences
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PHAGOCYTOSIS:
•
surrounding and transporting of large substances
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PINOCYTOSIS:
•
vacuole formation within a cell; carries liquid in/out of
cell
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EXOCYTOSIS:
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removal of large molecules from the cell
CELL GROWTH
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Organisms get
larger by producing cells
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As cells increase
in size the volume increases faster than the surface area
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example: diameter of cell increases 10x, surface area
increases 100x, volume increases 1000x
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The larger the
cell, the harder it is to get oxygen and nutrients; transcription and protein
synthesis becomes difficult
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cells compensate for cell growth by cell division
CELL DIVISION
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Cells divide to
form 2 cells
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Cell division
occurs in 2 stages
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mitosis - nucleus of cell divides into 2 nuclei
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cytokinesis - cytoplasm divides into 2 cells
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complicated process due to the fact that there are many
chromosomes that need to be passed on
CHROMOSOMES
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They are not
visible most of the time
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only during mitosis
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They contain the
genetic code (DNA)
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Each organism
contains a set amount
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humans have 46
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They are made up
of chromatin
CELL CYCLE
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Beginning of one mitosis to the beginning of the
next
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cell grows, prepares
for division, divides into 2 cells
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contains different
stages
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mitosis - active division (M
phase)
•
interphase
- period of non-division (G1, S, G2)
MITOSIS
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PROPHASE
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longest phase (50-60% of total time)
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chromosomes appear and attach to spindle
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centrioles separate and migrate to poles
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nucleolus disappears and nuclear envelope breaks down
MITOSIS
w METAPHASE:
•
Shortest phase
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chromosomes line up at equator
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starlike microtubules (asters) appear
MITOSIS
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ANAPHASE:
•
centromeres
split
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sister chromotids
separate, move to the poles
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spindle grows longer
MITOSIS
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TELEPHASE:
•
Chromosomes uncoil
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nuclear envelope reforms
around chromatin
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nucleolus forms
INTERPHASE
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Usually long time period
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3 stages:
•
G1 - gap 1: growth development
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S - synthesis: DNA synthesis
and protein are made
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G2 - Gap 2: short phase that makes organelles and
materials required for cell division
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nucleus synthesizes
mRNA
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cell makes protein, DNA
is copied, ATP is made
Control of the Cell Cycle
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Enzymes control
normal functions
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Enzyme production
is controlled by genes
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When normal
control fails, cells can divide at an uncontrolled rate (Cancer)
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Causes of cancer:
both genetic and environmental
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Prevention:
healthy diets and exercise, not using tobacco products