biology a tour of the cell
TRANSCRIPT
Biology
A Tour of the Cell
http://www-micro.msb.le.ac.uk/MBChB/bloodmap/Blood.gif
Microscopy
• A cell is the smallest unit of life. • They can vary in size, shape and
function (structure determines function).
• The light microscope led the way to knowledge of the cell.
http://www.microscope-microscope.org/basic/microscope-images/138-microscopes-lg.jpg
Microscopes:
• A light microscope magnifies objects (specimens) ~1000x their size. Most cellular structures CANNOT be seen.
• You will work with a light microscope in the lab.
http://www.dsbn.edu.on.ca/schools/Westlane/Science/simon/SBI3C1/micro.gif
• Electron microscopes give more detail and magnify a million times the object’s size.
• However, the organism dies when using an electron microscope.
There are 2 types of electron microscopes: • A scanning electron microscope (SEM) gives
a 3D image of a specimen/object.
• A transmission electron microscope (TEM) transmits electrons to view the interior of an object.
http://w3.salemstate.edu/~pkelly/sem/image003.jpg
SEM
How the Scanning Electron Microscope works:
TEM How the Transmission Electron Microscope works:
http://img72.imageshack.us/img72/2392/071003100546198ddedh5.jpg http://www.st-andrews.ac.uk/~dclogan/Fig3.jpg
SEMTEM
A history lesson:
• Robert Hooke (1665) named the cell after looking at cork under the microscope.
http://www.google.com/imgres
• Anton van Leeuwenhoek (LAY-von-hohk) (1670’s) developed a simple light microscope & discovered unicellular organisms and called them “little beasties”.
• Rudolf Virchow (1855) stated that all cells came from pre-existing cells (a.k.a. Cell Theory).
http://www.google.com/imgres
The Cell Theory (Virchow) has 3 basic
principles:
1. Cells are the basic units of life.
2. All organisms are made of 1 or more cells.
3. All cells arise from existing cells.
http://www.leksikon.org/images/virchow_rudolf.jpg
http://www.dmturner.org/Teacher/Pictures/Cell%20reproduction.jpg
Cell Structures: • All cells have an
enclosure called a cell, or plasma membrane.
• This functions as the gate keeper and controls what enters and exits the cell.
• It is mainly composed of phospholipids and proteins.
http://www.google.com/imgres
• Within the cell is the cytoplasm. This is a semifluid substance that contains the organelles.
• The organelles are small structures that have specific functions within the cells.
http://www.google.com/imgres
• The cytoskeleton is a protein network within the cytoplasm that helps support the cell and helps the cell maintain or change its shape. It also
– Anchors organelles
– Enables the cell to move
– Allows materials to move throughout the cell
– Composed of microtubules & microfilaments
http://www.google.com/imgres
• The nucleus is the control center of the cell
– It is surrounded by the nuclear envelope
– It contains the chromosomes. There are 46 chromosomes in the human nucleus (in every cell of the human body). The chromosomes are the DNA (genetic material).
• The nucleus is only found in eukaryotic cells!
http://www.google.com/imgres
• The nucleus contains the nucleolus
(if more than 1, nucleoli).
• Nucleolus: makes ribosomes
• Ribosomes
make proteins.
http://www.google.com/imgres
2 Types of CellsProkaryotic Cells • Bacteria• NO organelles
(membrane-bound structures)
• Contained w/in cell membrane & cell wall, contain ribosomes, 1 circular chromosome in nucleoid region (NO nucleus) & plasmids (extra pieces of DNA)
Eukaryotic Cells• Protists, Fungi, Plants,
& Animals• Contained w/in cell
membrane (may have a cell wall)
• Contain nucleus & other membrane-bound organelles
• Means ‘true kernel’
There are 2 types of cells:
1. Prokaryotes: These are bacteria (in Kingdom Monera).
– They are unicellular organisms.
– These were the first cells. They are very small cells and are very simple cells.
http://www.singleton-associates.org/gifs/cell.jpg
2. Eukaryotes: found in all other kingdoms except Monera.
– These have a nucleus (as well as a cell membrane and the majority of the organelles being discussed, depending on the type of organism).
http://www.google.com/imgres
Animal Cell: http://www.animalport.com/img/Animal-Cell.jpg
http://micro.magnet.fsu.edu/cells/plants/images/plantcell.jpg
• Ribosomes make proteins from amino acids; can be found suspended within the cytoplasm or attached to the endoplasmic reticulum. (not really organelles; these are cellular components)
• The endoplasmic reticulum (ER) is a network of membrane that produces materials for the cell. There are 2 types:
– The rough ER contains ribosomes and functions in protein synthesis and makes new cell membrane.
– The smooth ER makes lipids, process carbohydrates and breaks down toxins.
http://www.google.com/imgres
• The golgi apparatus is composed of flat membranous save that modify, package and distribute molecules (warehouse of the cell).
http://www.google.com/imgres
• Vacuoles are membrane-bound organelles that have various functions. – Some store food, water,
proteins, ions, or wastes. Generally these are large and centralized.
• Lysosomes contain digestive enzymes that break down large molecules and old organelles that the cell no longer needs.
Vacuole
http://www.google.com/imgres
• Chloroplasts, double-membrane-bound organelles, perform photosynthesis. – This is the process of
making sugar (synthesis) in the presence of light (photo).
– Plants (some bacteria & protists) make their own food (a.k.a. autotrophic).
http://www.daviddarling.info/images/chloroplast.jpg
• The mitochondria is the “powerhouse of the cell” b/c it changes stored enter from food into useable chemical energy (ATP) for chemical reactions. – ATP = adenosine triphosphate (energy ‘currency’
of cells)
– The chemical reactions are cellular respiration.
http://scienceblogs.com/worldsfair/Mitochondria.jpg
• Cilia are short hair-like projections that are in the surface on the cell usually in large number. (NOT organelles)
– Beat in unison and aid in the cell’s movement or in the movement of fluid over the cell.
Cellular Structures
http://www.google.com/imgres
• Flagella are long tail-like projections that are on the surface of the cell. (NOT organelles)
– Usually 1 to 3 of these.
– In prokaryotic cells, they spin like propellers.
– In eukaryotic cells, they move like whips.
http://www.google.com/imgres
Plants differ from animal cells. In plants:
• A cell wall surrounds the cell membrane.
• The cell wall is a rigid outer covering that protects and maintains the shape of the plant cell.
• Fungi, algae (a type of protist) and bacteria also have cell walls but the composition is different.
Cell Wall
http://www.google.com/imgres
• Plants LACK lysosomes.• Animals are heterotrophic, meaning
they must consume food.
Animal cells:• LACK a cell wall but have cytoskeletons
for structural support. • LACK chloroplasts• Contain small vacuoles (instead of a
large centralized one)• Have lysosomes
BOTH Animal and Plant Cells Contain:
• Organelles previously mentioned (nucleus, ER, mitochondria, ER, ribosomes, etc)
• Cell membranes• DNA (in chromosomes)
SEMI-PERMEABLE MEMBRANE
• Cell/plasma membrane is composed of a phospholipid bilayer (2 layers of phospholipids) with proteins interspersed.
• Phospholipids have a hydrophilic head & hydrophobic tail
• Fluid & flexible
http://www.bioteach.ubc.ca/Bio-industry/Inex/graphics/phospholipid.gif
http://www.hallym.ac.kr/~de1610/histology/cell-3.jpg
Cell Membrane
Membrane Functions • Cell membranes are semipermeable. This
means that some things pass through the membrane while others cannot pass through (this depends on the size & charge of the molecule).
• Passive transport is the movement of a substance across a membrane without energy input.
• Active transport is the movement of a substance across a membrane with the input of energy.
• Concentration=[ ].
• Molecules move from a higher [ ] gradient to a lower [ ] gradient.
• A [ ] gradient is the difference between the [ ] of a particular molecule in 1 area and its [ ] in an adjacent area.
• The rate of diffusion depends on temperature and size of molecules involved (molecules move faster at higher temperatures and smaller molecules move faster than larger molecules).
• Once molecules are dispersed evenly, equilibrium is reached and diffusion stops.
• Diffusion is the movement of molecules from a higher concentration to a lower concentration.
Passive Transport
http://www.google.com/imgres
• Facilitated diffusion is the diffusion of molecules with the help of a carrier protein embedded within a cell membrane.
http://www.google.com/imgres
• Osmosis is the diffusion of water.
• Diffusion, facilitated diffusion and osmosis are all type of passive transport. These do NOT require energy (occur spontaneously).
http://www.biologycorner.com/resources/osmosis.jpg
• Active transport in cells usually occurs with the help of carrier proteins but REQUIRE energy. An example is the sodium-potassium pump (Na+/K+ pump).
http://web.ahc.umn.edu/~mwd/cell_www/images/Na-Kpump.png
• When comparing 2 solutions with a membrane between them, there are 3 types of solutions:
• Hypertonic: the fluid outside a cell has a higher [solute] than the cytoplasm inside the cell. In this case, water diffuses out of the cell.
• Isotonic: the [solute] outside the cell= the [solute] inside the cell. In this case, no osmosis will occur.
• Hypotonic: the fluid outside a cell has a lower [solute] than the cytoplasm inside the cell. In this case, water will move inside the cell.
http://kentsimmons.uwinnipeg.ca/cm1504/Image130.gif
Bulk Transport:1. Exocytosis:
exo=exit; cyto=cell• Wastes and cell
products are packaged in vesicles by the golgi apparatus.
• The vesicles fuse with the cell membrane and leave the cell
http://www.octc.kctcs.edu/gcaplan/anat/images/Image152.gif
2. Endocytosis: endo=within; cyto=cell
• A portion of the cell membrane surrounds a substance outside of the cell & pinches off to form a vesicle
• The vesicle moves inward and fuses with other organelles
• This includes
– Pinocytosis: cell drinking
– Phagocytosis: cell eating
http://www.gla.ac.uk/~jmb17n/Teaching/L2teaching/Agpres/Figures/Endocytosis.jpg
To review cell structures and reproduction, click on these links and do some activities:
http://www.cellsalive.com/cells/cell_model.htm
http://biolabs.wikispaces.com/Cell+Drawings