Download Cells

Cells
Structure and Function
What We Will Learn
• How were cells discovered?
• What are the basic differences between
types of cells?
• How are cells structured?
• What are the functions of different cell
structures – how do they work?
Cellular Basis of Life
• Cell
– Smallest living unit of any organism
– Capable of carrying out all life functions
• Uni-cellular life – single cell
• Multi-cellular life – many cells with different functions
History of Cell Discovery
• Most cells too small to
see with naked eye
• Invention of
microscope enabled
scientists to discover
and study cells
Scientists and Cell Study
Leewenhoek:
– Simple microscope
– Observed organisms in pond
water, blood cells, bacteria
Hooke:
– Crude compound microscope
– Observed cell walls of cork
– Coined term “cells”
Schleiden: (Botanist)
– Stated all plants are made of cells
Schwann: (Zoologist)
– Stated all animals made of cells
Virchow:
– Stated all cells come from
pre-existing cells
Brown:
– First to identify an internal
cell structure (nucleus)
From this research and observation of living
things a scientific theory was developed
(took over 200 years!)
Cell Theory
1. All living things made up of cells
2. Cells are the basic units of structure
and function in living things
2. New cells come from existing cells
Exceptions to Cell Theory
Viruses:
– Need host cell to carry out life processes
Exceptions to Cell Theory
Mitochondria & Chloroplasts:
– Organelles that reproduce inside cell
– Have own unique genetic material
– Can’t survive outside of cell
Exceptions to Cell Theory
The First Cell
• Where did it come from?
• What was it like?
2 Basic Types of Cells
• Prokaryotes
• Eukaryotes
Both Types:
– Contain DNA
– Are surrounded by cell (plasma) membrane
– Carry out all life functions
Prokaryotes
– No nucleus
– Lack internal
membrane bound
organelles
– DNA in cytoplasm
– Metabolic functions
take place in cytoplasm
– Smaller, simpler more
primitive cells
• Ex: bacteria
Eukaryotes
– Nucleus encloses DNA
– Specialized membrane
bound organelles (more
compartmentalized)
– Larger, more complex
• Ex: protists, plants,
animals, fungi
Cell Structure and Organelles
The Cell as a Factory
• Each organelle carries out a specialized
function.
• Ex:
– Oversee cell activities
– Provide energy
– Produce products
– Get rid of wastes
Cell as Factory
Cell Membrane
• Also called “plasma
membrane”
• Separates inside of
cell from outside
environment
• Made of lipid and protein bi-layer
• Called the “fluid mosaic model”
• Controls substances going in and
out of cell (selectively permeable)
http://youtu.be/Rl5EmUQdkuI
Channel Proteins:
allow for selective movement of materials in and out
of cell membrane
Phospholipids: molecules that line up in a bi-layer
(two layers) to make cell membrane
Hydrophilic = “water loving” end
Hydrophobic = “water fearing” end
Cell Wall
• Found in plants, fungi,
some bacteria and protists
• NOT in animal cells
• Inflexible structure
• Made of cellulose fibers
woven together
– In fungi made of chitin
• Protect cell and give it
support and shape
Liquid, gel-like
substance inside
cell membrane
(75% water)
Many substances
dissolved in it
Most chemical
reactions take place
here.
Cytoplasm
“Cyclosis”: the movement of
materials through cytoplasm
http://youtu.be/7jw-N82tHjc
Cytoskeleton
• Internal framework
inside cytoplasm
• Made of fibrous rods
– microfilaments
– microtubules
• Maintains cell shape
• Supports and moves
organelles
Images of Cytoskeleton
Nucleus
• Directs cell activities
• Eukaryotic Cells ONLY!!
• Control center for metabolic functions and
reproduction
• Provides instructions for making proteins and
other molecules for the cell
Structure of
the Nucleus
Nuclear envelope: membrane surrounding nucleus
Nuclear pores: allow materials to leave or enter
Nucleolus: dark inner area. Ribosomes formed here
Chromatin:
• coiled DNA, in the
nucleus
• contains instructions
for building proteins
• unwound and spread
out
• Communicates with rest of cell by
movement of molecules through nuclear
pores
• During cell division, chromatin condenses
to form chromosomes that replicate and
divide
Endoplasmic Reticulum (E.R.)
• Channels to move materials inside cell
• Highly folded (increases surface area)
Rough ER:
“bumpy” with ribosomes
attached to surface
Smooth ER:
doesn’t have ribosomes
on surface
Ribosomes
• Site of protein synthesis
• Small round structures
• Cell has a lot of them
(needs proteins!)
• May be free floating in
cytoplasm or attached to
the “rough” E.R.
Golgi Bodies
• Stack of
membranes
(like pancakes)
• Involved in
modifying,
packaging,
storing and
releasing
products
Vesicles:
packages containing proteins that are
pinched off to be used inside cell or
transported out.
Lysosomes
• Membrane enclosed vesicles
• Hydrolytic digestive enzymes
• Breaks down food and worn out cell parts
• Formed by Golgi Bodies
http://youtu.be/ekdIEpSf-1I
Vacuoles
• Stores water, food,
wastes
• Much larger in plant
cells
– Used to help give cell
shape, structure
• Food Vacuoles: merge with lysosomes to
digest food
Contractile Vacuoles:
– Found in single celled freshwater
organisms like paramecium
– “contract” to pump out excess water
from cell
Energy and the Cell
Mitochondria
• Powerhouse of the cell
• Site of cellular respiration
• Makes usable energy
(ATP)
• Simple sugars are broken down to release
energy as ATP
• The more energy a cell needs the more
mitochondria it has!
Cristae:
Highly folded inner membrane that allows for
increased surface area for cellular respiration
reactions
Chloroplasts
• FOUND IN PLANT CELLS ONLY!!
• Site of photosynthesis
Light energy is transformed to chemical
energy in the form of sugar
• Chlorophyll: (green pigment) that
captures sunlight
• Grana: Inner
membranes in
“coin” stacks
containing
chlorophyll
• Stroma: enzyme
filled fluid
surrounding
grana
Endosymbiotic Theory
• Mitochondria and chloroplasts have own DNA
and can reproduce on their own.
• Perhaps they were a primitive type of prokayotic
cell that became incorporated into another
• Symbiotic relationship = both cells benefit
Evolution of Complex Life
http://youtu.be/q71DWYJD-dI
Centrioles
• FOUND IN ANIMAL CELLS ONLY!!
• Pair of small cylindrical organelles found
near nucleus
• Function in cell division to pull
chromosomes apart
Cell Movement
• Cilia: short hair like projections used for
locomotion
• Flagella: long whip-like tail used for
locomotion
• http://youtu.be/QGAm6hMysTA
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Pseudopods: “false foot”
Projections of the cell membrane
Used for locomotion
Used to surround and engulf food
Limitations of Cell Size
• Size is limited by the cell’s need to intake
nutrients and excrete wastes
• Smaller the cell is, the closer all parts are
to the external environment.
• Surface area to volume ratio
• http://www.youtube.com/watch?v=rnNAcLJNc3s&feature
=share&list=ULrnNAcLJNc3s
• http://youtu.be/LP7xAr2FDFU
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Passive transport
http://youtu.be/JShwXBWGMyY
Osmosis
http://youtu.be/XclGRjnilsk
Membrane
http://youtu.be/GW0lqf4Fqpg
Cellular Organization
• In multicelluar organisms cells are just the
start of how things are organized.
– Cells
– Tissues: groups of cells that function together
to perform an activity
– Organs: groups of tissues performing one
main function
– Organ Systems: organs working together
– Organism