organelles nucleus : a cell's center - ednet.ns.cahrsbstaff.ednet.ns.ca/allenas/biology...
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Biology 11
A. Allen
Cytoplasm (cytosol): a cell's inner space
cytosol
Cytosol: large fluid-filled space (mostly water + proteins that control
most of the cell metabolisms): glycolysis, transcription
factors, intracellular receptors etc.
Plasma
membrane
Organelles
• Nucleus
• Protein production machine: the ribosomes
• Mitochondria and Chloroplasts
• Endoplasmic Reticulum and the Golgi apparatus
• Lysosomes and Peroxisomes
• Adapted and/or specialized for carrying out one or more vital functions
Reminder! Membrane-bound
organelles are only found in
eukaryotes.
Nucleus: a cell's center
Function of the nucleus:
• Stores the chromosomes (genetic material) Note: Two kinds of genetic material:
– deoxyribonucleic acid (DNA)
– ribonucleic acid (RNA)
• Keeps the DNA molecules separated from metabolic machinery of cytoplasm.
• Makes it easier to organize
DNA and to copy it before
parent cells divide into
daughter cells
• DNA replication and
synthesis of messenger
RNA (mRNA). The
mRNA is allowed to leave
the nucleus. It is read by
the ribosomes during
protein synthesis.
...Nucleus: a cell's center Nucleolus
• Dense mass of
material in nucleus
• Cluster of DNA and
proteins
• Subunits must pass
through nuclear pores
to reach cytoplasm
• production of
ribosomes in nucleolus
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• Two outer membranes (lipid bilayers)
• Pores span bilayer and controls what
enters/leaves nucleus.
Nuclear Membrane (Envelope) Chromatin
• Cell’s collection of DNA and associated proteins
• A chromosome is one DNA molecule and its associated proteins
• Appearance changes as cell divides
FUNCTION:
• With the help of tRNA, ribosomes use information in mRNA to assemble proteins
• small semi-spherical, black dots
• some are free in cytoplasm (cytoplasmic ribosomes), others are attached to the ER (ER ribosomes)
Ribosomes
STRUCTURE
• ER is a continuation of the outer nuclear membrane.
• Two types: Smooth and Rough. (Rough ER has ribosomes on it)
• Network of membrane that connects nuclear envelope to the cell
membrane
Endoplasmic Reticulum (ER)
…Endoplasmic Reticulum (ER)
FUNCTION:
• Smooth ER (no ribrosomes): responsible for lipid and membrane
protein modifications)
• Rough ER (has ribosomes on it) responsible for the synthesis of
other proteins). The ribosomes assemble the proteins within the
rough ER. Once assembled, the proteins pinch off the ER and are
released in a vesicle.
Endoplasmic Reticulum (ER)
…Endoplasmic Reticulum (ER)
3
FUNCTION:
• processes, packages, and, secretes cell products (lipids & proteins)
• Put finishing touches on proteins and lipids that arrive from ER
• Package finished material for shipment to final destinations. (Exocytosis)
• Material arrives
and leaves in vesicles
Golgi Body (Golgi Apparatus) …Golgi Body (Golgi Apparatus)
STRUCTURE
• Double membrane. Inner membrane is
folded for greater surface area. Folds
are called cristae.
• Interior is called the matrix.
• Contain their own genome (distinct
from nuclear genome)
• Self-replicating
FUNCTION
• ‘burns’ food, i.e. glucose to release
energy. Energy is used to make ATP.
ATP is a high-energy molecule that
can be directly used by the cell.
Mitochondria
The “powerhouse” of the cell
…Mitochondria
STRUCTURE
• Formed by Golgi bodies
• Bound by a single membrane
FUNCTIONS
• Digests the food particles inside the cell with help of enzymes. These enzymes work at low pH.
• Involved in autolysis (suicide of cell)
• Digest foreign bacteria that invade a cell
• Recycling of membrane components
• Repair damage to plasma membrane
Lysosomes
• Made by Golgi
• Surrounded by a single membrane
• Get rid of toxic substances
• Many in the liver/ brain
lysosome
Peroxisomes
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FUNCTION:
• maintains the shape of a
plant cell
• found in plants, some fungi,
some protists
• In plants, cell walls are made
of a polysaccharide called
cellulose.
• Structural component that
wraps around the plasma
membrane
Cell Wall …Cell Wall
FUNCTION:
• Photosynthesis: converts sunlight, carbon dioxide,
and water into sugar (makes food for plants)
Chloroplasts
• A large membrane bound sac
FUNCTION:
• storage area for proteins and
water
• Maintain structure in plant cells by means of turgor pressure
Vacuole
• very complex and dynamic cell component!
• organizes and maintains the cell's shape (e.g. epithelial cells of the
gut)
• anchors the organelles in place
• helps during the uptake of external material (endocytosis)
• involvement in cell movement
• growth
Cytoskeleton: a cell's scaffold
microtubules microfilamentsintermediate filaments
tubulin actin keratin family
All help maintain cell shape
Cilia, flagellaChromosome movementOrganelle movement
Cytoplasmic streamingPseudopodiaCell division
Nuclear laminaAnchorage of nucleus and some other organelles
...Cytoskeleton
video
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...Cytoskeleton ...Cytoskeleton
Molecular
motors
...Cytoskeleton
Macrophage attacks bacteria
Microfilaments (actin) allow formation of pseudopods
...Cytoskeleton
Striated Muscle
...Cytoskeleton
Centrosome:Made up of centriole pairs
...Cytoskeleton
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Bibliography
• http://users.ipfw.edu/mustafaa/PQ_B100-02-ppt-Chapter4-Cell%20Structures%20and%20Functions.ppt
• http://images.google.ca/imgres?imgurl=http://biology.dbs.umt.edu/biol101/labs/lab_6_images/sect05and02/cheek%25
20cell%25201000x.jpg&imgrefurl=http://biology.dbs.umt.edu/biol101/labs/lab_6_images/sect05and02/section_2and5
_cellimages.htm&h=768&w=1024&sz=316&tbnid=OxmCr18W6AQJ:&tbnh=112&tbnw=149&start=1&prev=/imag
es%3Fq%3Dcheek%2Bcell%26hl%3Den%26lr%3D
• www.ops.org/burke/02science/organelles.ppt
• file:///C:/WINDOWS/Temporary%20Internet%20Files/Content.IE5/UPK3G94Z/266,12,Diffusion
• http://bioweb.wku.edu/courses/biol22000/11Organelles/images/F05-43A.JPG
• http://cellbio.utmb.edu/cellbio/nucleus.html
• http://www.cellsalive.com/cells/er.htm
• cellbio.utmb.edu/cellbio/ribosome.htm
• http://cellbio.utmb.edu/cellbio/golgi.htm
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