Transcript Cell Structures

Cell Structures
Movement & Organelles
Diffusion
 Movement of molecules from an area of
high concentration to an area of low
concentration
 Move to the lower concentration
Osmosis
 Diffusion of water
Osmotic Conditions
 Hypertonic Solution - contain a high concentration of solute relative
to another solution (e.g. the cell's cytoplasm). When a cell is placed
in a hypertonic solution, the water diffuses out of the cell, causing
the cell to shrivel
 Hypotonic Solution - contain a low concentration of solute relative to
another solution (e.g. the cell's cytoplasm). When a cell is placed in
a hypotonic solution, the water diffuses into the cell, causing the cell
to swell and possibly explode.
 Isotonic Solution – solution where parts are equal in solute and
solvent – water moves across the membrane freely
 http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
Cell Membrane
 1. regulates the flow of materials in & out
of the cell
 2. selectively permeable – only certain
materials pass thru
 3. made up of bilayer of phospholipids
with protein molecules jutting thru the
layers
Cell Wall
 Prokaryotic Cell Wall
 Some have a 2nd outer layer composed of





lipoproteins and lipopolysaccharides
Eukaryotic Cell Wall
3 parts – primary, middle lamella and secondary
cell wall
Primary cell wall – cellulose
Middle Lamella – polysaccharides = pectins
Secondary cell wall – cellulose and lignin
Cell Wall
 Eukaryotic Cell Wall
Prokaryotic Cell Wall
Movement Through Membrane
 Simple Diffusion
 Molecules pass thru phospholipids in the
membrane
 Only occurs for small non-polar molecules
Movement Through Membrane
 Passive Transport
 1. Protein channels
 A. Proteins can form tunnels thru which
molecules can diffuse
 B. Polar molecules can travel thru
Movement Through Membrane
 2. Facilitated Diffusion
 A. Carrier proteins bond to a molecule on one
side of the membrane, travel across and
releases it on the other side.
 B. Carrier proteins bond with specific
molecules (like enzymes do)
Movement Through Membrane
 Active Transport
 Works against a concentration gradient
 Requires an input of energy
 Contractile Vacuole is an example – it
forces excess water out of the cell even if
it is against osmosis

http://www.biologie.uni-hamburg.de/bonline/library/biology107/bi107vc/fa99/terry/images/ATPpumA.gif
Organelles
 Vacuoles – sacs in cell which hold food,
water, and enzymes
 Vessicles – small vacuoles formed from
part of Golgi bodies to hold proteins
 Lysosomes – sac contains digestive
enzymes to break down food or damaged
organelles
Vacuoles and Vessicles
 Vacuole
Vessicle
Organelles
 Nucleus – contains cell’s DNA, controls proteins
and their production
 “Cell’s brain”
 Surrounded by nuclear membrane which has pores to
allow RNA to pass thru into the endoplasmic
reticulum
 Nucleolus – inside nucleus, makes ribosomes
 Usually each nucleus has several nucleoli
Nucleus
Organelles
 Ribosomes
 Tiny structure responsible for protein
production
 Has its own ribosomal RNA
 Located in the endoplasmic reticulum
Endoplasmic Reticulum (ER)
 Network of tunnels running from nucleus
to Golgi bodies
 Rough ER contains ribosomes, Smooth
ER does not
 Function: carry proteins to the Golgi
bodies and make new cell membrane
Endoplasmic Reticulum (ER)
Golgi Bodies
 Stacks of membranous pouches at the
end of the ER
 Receive proteins from ER and send them
to other organelles by putting them in
vessicles
Mitochondria
 Where cellular respiration occurs
 Eukaryotes have thousands in their cells
 Inner folded membrane (cristae) where
respiration occurs
 Have their own DNA and can replicate
themselves
Mitochondria
Cytoskeleton
 Network of protein fibers allow the cell to





change its shape – four types
1. microtubules- involved in cell
reproduction
2. intermediate filaments – strength/shape
3. microfilaments – cell locomotion
4. microtrabeculae
– connect organelles
Plastids
(only found in plants)
 Chloroplasts
 green due to chlorophyll
 Have grana and thykaloids
 Photosynthesis occurs in thykaloids
Plastids
(only found in plants)
 Chromoplasts
 Are like chloroplasts but not green
 Allow photosynthesis to occur in different
lighting conditions
Plastids
(only found in plants)
 Leucoplasts
 Colorless, have no pigments
 Stores starch proteins and lipids
 Releases them when the cell needs them
Unicellular Movement
 Cilia
 Tiny hairs on outside of cell membrane
used for locomotion
Unicellular Movement
 Flagella
 Large hair on outside of cell membrane
used for locomotion
 Both are composed of microtubules
Unicellular Movement
 Psudopodia – not truly an organelle
 Extension of the cytoplasm which the rest
of the cytoplasm flows to
 Used for movement
 Surrounds and captures prey