A View of the Cell
Chapter 7The Discovery of CellsThe Plasma MembraneEukaryotic Cell Structure
Web links to study guides
Cell Theory All living things are made up of 1 or more cells.
A cell is the smallest unit that can carry on all of the
processes of life
Before the 17th century, no one knew that cells existed.
One of the 1st microscopes was made by the Dutch drapery store owner Anton von Leewenhoek. 1st person to observe & describe microscopic
organisms & living cells
Animalcules
Robert Hooke
1665 – Robert Hooke used a microscope to examine a thin slice of cork & described what he saw as “a great many little boxes”. He thought the boxes looked like small
rooms in which monks lived, so he called them “Cells”
Hooke’s microscope
Micrographia
Cell Theory
1838 – German botanist Matthies Schleiden concluded all plants are composed of cells.
1839 – German zoologist Theodor Schwann concluded that animals are made up of cells.
1855 – German physician Rudolf Virchow concluded that plant cells come only from a plant and animal cells arise only from an animal Cells only come from other cells!
Cell Theory – three main parts
All living organisms are composed of one or more cells.
Cells are the basic unit of structure & function in an organism.
Cells come only from reproduction of existing cells. This means that all cells came from ONE
original.
Light Microscopes
Light microscopes can magnify up to 1,500X and resolve objects as small as 200 nanometers (2x10-7)
Electron Microscopes
1st built by Ernst Ruska (1986 Nobel Prize) in 1933. He used accelerated electrons & magnetic coils
to make an image. EMS can resolve objects that are 103 time
smaller than the light microscope. Transmission EMS can magnify a sample
up to 50,000x and provide a resolution of 0.1 x 10-9 m.
Prokaryote - Eukaryote
Stuff Cells are made of
Intro Clip
Plasma Membrane Like a
“smart” security blanket for the cell.
Lets some molecules in and keeps others out
Plasma Membrane Lipid bilayers have 2 important characteristics
1. Polar molecules can stick together like magnets, but are not PERMANENTLY stuck like in a chemical bond.
2. Lipid bilayers are fluid.
(imagine life preservers floating on a pool with strings hanging down into the water)
What is a mosaic?
The patterns that the proteins make on the membrane make the surface look like a mosaic.
Phospholipid membrane Basic Building
Block of the cell membrane is the phospholipid.
Double layer of lipids forms a flexible lipid bilayer. (bi = 2)
Passage Ways
Proteins in the cell membrane serve many purposes.
Channels – Proteins act as passage ways through which only certain molecules can pass.
Receptors – Proteins transfer information into the cell by reacting to certain other molecules
Passage Ways
Markers – Proteins are the “name tags” of cells giving them identity.
Cellular Boundaries The plasma membrane
Acts as a selectively permeable membrane
Is flexible The cell wall
Plants, fungi, most bacteria and some protists
Fairly rigid Gives additional support and protection
Plant Cell Wall
Made up of carbohydrate Cellulose Forms a thick mesh Functions to protect the cell and give it
support ONLY Very porous – allows molecules to pass
through DOES NOT select what materials can enter
the cell – that is the cell membrane’s job
Control in the cell
Start with the Nucleus
1. Nucleus – leader of the eukaryotic cell. Contains the directions to make proteins in
chromatin – strands of DNA Remember, the types of proteins a cell produces are
what makes it unique Proteins are necessary for ALL functions of the cell We call this DNA chromosomes when it is all coiled
up before the cell reproduces itself
THIS is where all heredity information is stored
Cell Nucleus
Nucleus cont.
2. Nucleolus - inside the nucleus Assembles ribosomes that will move outside the
nucleus into the cytoplasm(more on ribosomes later, but they are the factories that
make proteins from amino acids)3. Nuclear Envelope – pair of membranes that
surround DNA & nucleolus4. Nuclear Pores – allows material to pass through
nuclear envelope5. Cytoplasm – fluid region between cell
membrane and nucleus
Cytoplasm
5. Cytoplasm surrounds the nucleus, suspends the organelles
Has two main components – Cytosol & organelles Cytosol – consists mostly of water along with
proteins, carbohydrates, salts, minerals, & organic molecules.
Organelles (Endoplasmic reticulum, mitochondria etc.) carry out specific functions in the cell
Ribosomes
6. Ribosomes - manufacturing centersA. This is where proteins are made.B. Free ribosomes – scattered throughout
the cytoplasm. Produces proteins used in the cell.
C. Fixed ribosomes – produce proteins used outside the cell
Endoplasmic Reticulumthe chemical reaction center
7. Endoplasmic Reticulum – a large workspace within the cell
Complex system of membranes that forms a transport system between the nucleus and the cytoplasm
May have ribosomes attached – Rough ER. No ribosomes – Smooth ER
Smooth Endoplasmic Reticulum
7a. Smooth ERA. Builds lipids for cell membraneB. neutralizes poisons (will break down
morphine & amphetamines)
Rough Endoplasmic Reticulum
7b. Rough ERA. Ribosomes attached
B. sites for proteins that are exported
Golgi Bodies8. Molecular mail of
the cellA. saclike pieces of
membrane pinched off that are full of chemicals
Ex – found in cells that produce large number of chemicals – saliva & digestion aids
Mitochondria
9. Power houseA. Releases energy from the nutrients taken inB. Ex – Found in greater numbers in liver cells &
heart cells
Lysosome10. Lysosome -
recycling centers of the cell
A. Contain strong destructive enzymes that break down food & foreign objects
Ex – Found in white blood cells
Stuff for Lysosomes to destroy…
Cytoskeleton11. Maintain the shape of
cell & hold organelles in place Microtubules- hollow
tubes like plumbing pipes
Microfilaments- have a structure that resembles rope and can contract causing movement.
Muscle cells have many microfilaments
Centrioles
12. Centrioles organize the microtubules of the cytoskeleton during cell division in animal cells
Plant cells don’t have centrioles
Cilia & Flagella
13. Cilia & Flagella - Hairlike organelles that extend from the surface of the cell, where they assist in movement Cilia- short hairlike projections Flagella- long whiplike projections
In humans beating cilia line parts of the respiratory system, moving dust particles & bacteria away from the lungs
Vacuoles14. Vacuoles are membrane-bound spaces in the
cell used for storage of materials. Examples of things the vacuole may store are food,
enzymes and waste. Vacuoles are difficult to see in animal cells, since they are
so small.
Plant vs. Animal Cells
1. Both have the same organelles.2. Both are Eukaryotic cells.
Plants have 1. Large vacuoles – may take up to 90%
of the volume of a cellA. gives support to the cellB. stores food or waste material
Animal cell Usually smaller in size Cell wall is absent. Cellulose in any form is absent Cytoplasm is denser, more granular and occupies most of the space in the cell . Vacuoles absent. If present, they are small, temporary and concerned with excretion or secretion Vacuoles are large and prominent. May be one or more Plastids are absent Plastids are usually present Centrosome is present Centrosome is absent. Instead two small clear areas called polar caps are present Prominent and highly complex Golgi bodies present near nucleus Contain several sub units of Golgi apparatus called dictyosomes
Plant cell Usually larger in size Cell wall made up of cellulose is present Cytoplasm is pushed to the periphery and forms a thin lining against the cell wallThe central space in the cell may be occupied by a large, single vacuole
Plant Cells
2. Chloroplasts –contains chlorophyll (gives the plant leaves their green color)
A. site of photosynthesis
Plant Cells
3. Chromoplasts – color pigments found in flower petals (red, orange, and yellow)A. no known chemical function
in the cellB. attracts animals & insects to
the flower
Plant Cells
4. Leucoplasts – colorless vacuolesA. storage for starch and fat molecules
5. Cell Wall – thick outer layer that protects & supports the cell.A. made of cellulose
Top Related