cell structure & function
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CELL STRUCTURE & FUNCTION
CHAPTER 4 MISS COLABELLI
THE DISCOVERY OF CELLS
• All living things are made up of one or more cells• A cell is the smallest unit
that can carry out life processes
THE DISCOVERY OF CELLS
• Robert Hooke• English scientist that studied nature using a light
microscope• Looked at thin slices of cork from bark on a cork oak tree• Noted there were empty pores throughout the specimen
that resembled cells the monks would live in• Noticed other plant specimen had the same organization
of boxes
THE DISCOVERY OF CELLS
• Anton van Leeuwenhoek• First person to observe living cells• Made his own light microscope• Observed microorganisms such as algae
and protists
THE DISCOVERY OF CELLS
• The Cell Theory• A composition of understandings from different
scientists that all cells must go by1.All living things are composed of one or more cells2.Cells are the basic units of structure and function in
an organism3.Cells come only from the reproduction of pre-existing
cells
CELL DIVERSITY• Cell Size• Cells are limited by the relationship of their
outer surface area to its volume• As a cell grows, its volume increases much faster
than the surface area• Important to know because nutrients and wastes need
to move though the cell efficiently• A cell too large would take too long to diffuse these
materials and it can harm the cell• Most cells are better off being smaller and keeping their
surface area to volume ratio bigger
• Plasma Membrane• Cell’s outer boundary• Covers the cell’s surface and acts as a barrier
between inside and outside of the cell
• Cytoplasm• Area within the cell that contains the fluid,
cytoskeleton, and the organelles
• Nucleus• Membrane-bound area of the cell that contains
genetic information• Controls the function of the cell
TWO BASIC TYPES OF CELLSPROKARYOTE• Organisms that lack a
membrane-bound nucleus and membrane-bound organelles• General area of cell
where genetic information is located is called the nucleoid• Usually bacteria and
archaea
EUKARYOTE• Contain a
membrane-bound nucleus and organelles with membranes• Organelles carry out
functions for the cell• Usually plant and
animal cells
http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm
PLASMA MEMBRANE
• Membrane Lipids• Made of two layers of phospholipids
(phospholipid bilayer)
• Membrane Proteins• Specific proteins embedded in the lipid bilayer• These proteins help with transporting molecules
across the membrane and act as receptors • Send messages to the rest of the cell
INNER LIFE OF THE CELL
http://www.youtube.com/watch?v=B_zD3NxSsD8
NUCLEUS• Houses and protects the cell’s genetic information
• Contains instructions for the structure and function of the organism
• Before a cell divides, the DNA condenses to form chromosomes• Nuclear envelope
• Double membrane that surrounds the nucleus• Made of two phospholipid bilayers• Contains pores (holes) called nuclear pores for RNA and
other materials to enter and leave the nucleus
• Nucleolus• Dense area in the nucleus where DNA is concentrated• Where ribosomes are produced
MITOCHONDRIA• Organelles that transfer energy from organic
matter (foods) to ATP• ATP powers most of the cell’s chemical
reactions• Highly active organelles• Two layer of membrane• Outer membrane holds cytosol• Inner membrane has folds called cristae where
energy-harvesting chemical reactions take place
http://www.youtube.com/watch?v=Ju0HxI5GWTo
MITOCHONDRIA•Mitochondrial DNA• Have their own DNA and
reproduce on their own• Scientists think
mitochondria originated from prokaryotic cells and were incorporated into eukaryotic cells• Called the endosymbiotic
theoryhttp://www.sumanasinc.com/webcontent/animations/content/organelles.html
RIBOSOMES• Small, spherical organelles that are responsible for
synthesizing proteins• Do not have a membrane• Made of protein and RNA molecules• Synthesized in the nucleus• Made of two subunits • Some are free in the cytoplasm and some are
attached to another organelle called the endoplasmic reticulum
ENDOPLASMIC RETICULUM (ER)
• System of membranous tubes • Functions as a highway for molecules to
move throughout the cell• Two types of ER• Rough ER • Smooth ER
ROUGH ENDOPLASMIC RETICULUM• System of interconnected tubes covered with
ribosomes• Ribosomes make it look “rough”
• Area where some proteins are made
SMOOTH ENDOPLASMIC RETICULUM• Lacks ribosomes and looks smooth• Builds lipids like cholesterol and hormones
for the body• Helps detoxify drugs and poisons• Liver cells contain a high amount or smooth ER
cells • Long-term drug and alcohol users also increase
their smooth ER organelles in their cells
GOLGI APPARATUS
• System of flattened sacs• Sacs near the nucleus receive vesicles from
the ER that contain newly made proteins and lipids• Vesicles travels through the Golgi
• Golgi apparatus “stamps” the vesicles to where they need to travel to in the cell• Like address labels
VESICLES• Small sphere like sacs that are surrounded by a
single membrane• Lysosomes
• Vesicles that bud from the Golgi and contain enzymes that break down large molecules
• Also help break down cells when it is time for the cell to die
• Peroxisomes• Similar to lysosomes except contain different enzymes• Neutralize radicals and detoxify alcohol and drugs• Produce hydrogen peroxide as a product in their chemical
reactions
http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/microtubuletransport.swf
CYTOSKELETON
• Network of thin tubes and filaments that crisscross the cytosol• Give the cell its shape
• Like poles in a tent
• Internal tracks where items in the cell move around the cell• Three different types of tubes found in the
cytoskeleton• Microtubules• Microfilaments• Intermediate filaments
MICROTUBULES
• Hollow tubes made of protein called tubulin• Radiate outward from the center called centrosome
near the nucleus• Hold organelles in place• Maintain cell shape• Act as tracks to guide organelles and molecules as
they move within the cell
MICROFILAMENTS
• Smaller than microtubules• Long threads of bead like protein called actin• Contribute to cell movement• Crawling white blood cells• Muscle contraction
INTERMEDIATE FILAMENTS
• Rods that anchor the nucleus and organelles in place• Maintain internal shape of the nucleus• Make up most of the hair shaft
CILIA AND FLAGELLA
• Hair like structures that extend from the surface of the cell• Assist in movement• Cilia• Short and present in large numbers
• Flagella• Long extensions of the cell, usually one that
helps with the cell moving
CENTRIOLES
• Two short cylinders of microtubules at right angles to each other• Near the nuclear envelope• Occur only in animal cells• Organize microtubules of cytoskeleton during
cell division
PLANT CELLS• Most of the organelles and parts of the cell are in all
eukaryotic cells• Plants have three additional structures
• Cell wall• Central vacuole• Plastids
CELL WALL• Rigid layer that lies outside the cell’s plasma
membrane• This cell wall is composed of the
polysaccharide cellulose• Primary cell wall• On top of the plasma membrane• Can grow in one direction
• Secondary cell wall• Between the plasma membrane and the primary
cell wall• Does not grow
CENTRAL VACUOLE
• Reservoir that stores large amounts of water, enzymes, wastes, and other materials• Large, fluid filled organelle• May take up 90% of the cell’s volume• When there is a lot of water the
vacuole fills up • When there is little water the vacuole
deflates
PLASTIDS• Double membrane organelles and contain
their own DNA• Chloroplasts• Use light energy and water to make food and
oxygen• Used in photosynthesis
COMPARING CELLSPROKARYOTE• Lack a nucleus• No membrane-
bound organelles• Region called
nucleoid• Bacteria and
archaea
EUKARYOTE• Have a nucleus• Membrane-bound
organelles• Plant and animal cells
COMPARING CELLS
PLANT CELL• Cell wall• Large central vacuole• Contain plastids
ANIMAL CELL• No cell wall• No vacuole• Contain centrioles
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