biology

Biology

A Tour of the Cell

http://www-micro.msb.le.ac.uk/MBChB/bloodmap/Blood.gif

• 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

(COMPOUND)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

http://www.nims.go.jp/htm21/MA/tem.jpg

SEM

http://img72.imageshack.us/img72/2392/071003100546198ddedh5.jpg http://www.st-andrews.ac.uk/~dclogan/Fig3.jpg

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).



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.



• 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.



• 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



• 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!



• The nucleus contains the nucleolus

(if more than 1, nucleoli).

• Nucleolus: makes ribosomes

• Ribosomes make proteins.



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 Kingdoms Archaebacteria and Eubacteria).

– 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.

– These have a nucleus (as well as a cell membrane and the majority of the organelles being discussed, depending on the type of organism).



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.

• The golgi apparatus is composed of flat membranous save that modify, package and distribute molecules (warehouse of the cell).



• 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



• 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



• 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.



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



• Plants LACK lysosomes and centrioles.• 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.

• http://www.sumanasinc.com/webcontent/animations/content/diffusion.html

http://www.sumanasinc.com/webcontent/animations/content/diffusion.html

http://www.sumanasinc.com/webcontent/animations/content/diffusion.html

• 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, DYNAMICequilibrium is reached and diffusion stops.

CLICK ON LINK:

http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html




• Diffusion is the movement of molecules from a higher concentration to a lower concentration.

Passive Transport



• Facilitated diffusion is the diffusion of molecules with the help of a carrier protein embedded within a cell membrane. CLICK ON LINK:

• http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html


http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html





• 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

http://road-to-rn.tumblr.com/post/127238852030/hypotonic-hypertonic-isotonic-solutions-videos




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

biology

Documents

cell http

cell membrane cell wall

gifa cell

sem http

cell theory virchow

preexisting cells

simple light microscope

human nucleus