Cells

IS3

Life•Possible origins:• Extraterrestrial• Supernatural (religious)• Chemical Evolution (inorganic → organic → cells)

•Requirements for life:• C, H, O, N, P, S• Sunlight/chemical energy• UV radiation protection• Water

“Found: first amino acid on a comet” 17 August 2009 by Maggie McKeehttp://www.newscientist.com/article/dn17628-first-amino-acid-on-a-comet-found.html

Cell Discovery

•Linked to microscope development

•1595 – Hans Janssen + son Zacharias (Dutch): credited with microscope invention

•Two main types: light and electron

Light Microscope

•Light passes through an object and 2 or more lenses•Possible to see living cells – not a lot of detail

•Advantages: • Object: can be living• Staining not required• Real colors visible• Easy to work with• But low resolution: up to 200 nm +low magnification: up to 2000X

Electron Microscope

•Two types• Scanning Electron (SEM)– uses electron beams that bounce off

the specimen

• Transmission Electron (TEM)– Used electron beams that pass

through specimen

•Advantages: • more detail / higher resolution (0.2nm) /

magnification: close to 1 million X• But specimen must be dead + colors aren’t

real.

Transmission Microscope (guess what these structures are...)

Scanning Microscope

Timeline•Anton van Leeuwenhoek (Dutch – 1632-1723)•Improved simple microscope (single lens – magnification up to 270 X)•First to see living cell (red blood cells, sperm cells, single celled organisms)

Timeline•Robert Hooke (English – 1635-1703) •Looked at a piece of cork – first to use the term "cell“•Improved microscope: compound (2 lenses)•1800 – scientists knew cells had a cell membrane, a nucleus, cytoplasm and cell wall

Timeline

•Mathias Schleiden – (German botanist – 1804-1881) • all plants are made of cells

•Theodor Schwann (German zoologist – 1810-1882) • all animals are made of cells

•Rudolf Virchow (German physician – 1821-1902)• concluded that all cells come from other cells

Cell Theory

•All organisms are made up of one or more cells.•Cells are the basic units of structure and function in all organisms.•All cells come from cells that already exist.

•Exception:–Viruses are non-cellular structures of DNA or RNA that are

surrounded by a protein coat

Single-cell x Multicellular

•Organisms can be made up of one cell (single-celled) or many cells (multicellular).

•Single-celled organisms are the bottom of the food chain

•There are more single-celled organisms than multicellular organisms in the world.

Single Cell OrganismsOne cell carries out all functions:•Metabolism: all chemical reactions happening at the same time•Response: sense environment•Homeostasis: regulate/balance reactions in the body according to the environment conditions•Growth: production of new organelles•Reproduction: division •Nutrition: release energy from food

Amoeba Paramecium

Multicellular Organisms

•Interaction•Communication•Cells specialize: they differentiate because some genes are expressed and some are not (on/off) depending on the type of cell.• Neuron• Muscle cell• Skin cell

•Stem cells = not specialized = ability to differentiate into specialized cells

Trypanosoma

Diatoms

Why are cells small?•Surface area to volume ratio limits cell size•Rate of heat production/waste/resource consumption – volume•Rate or exchange material/energy – surface area•As cell size increases, the surface area to volume ratio decreases•Metabolic rates increase faster than the surface area’s ability to exchange nutrients, hence a maximum size is reached.•Cell size, therefore, remains small

SIZE OF VARIOUS CELLS AND STRUCTURES

Molecules: 1 nmMembranes (on organelles): 10 nm

Viruses: 100 nmBacteria: 1 um

Organelles: up to 10 umMost cells: up to 100 um

Measurements above in 2d, remember all structures have 3d shape.

Cell Organization

Cells differ:•Size•Shape

Types of CellsTypes:•Prokaryotic (no nucleus + naked DNA in cytoplasm + only ribosomes)Example: Bacteria

•Eukaryotic (with nucleus + organelles)Example: Animals, Plants, Fungi, Protists

Cell Membrane•Outer boundary: phospholipid bilayer•Communication between cells•Selects what goes in and out (using energy – active transport or without using energy – passive transport)•Animal cells have cholesterol in the membrane

Cell OrganellesOrganelle - structure within a cell that has a specific function.

•Endoplasmic Reticulum – membranes that move materials around in the cell (“transport system”)

•Ribosomes – make proteins (“factories”)

•Centrioles (animals only) – coordinate cell division

Cell Organelles•Mitochondria – produce ATP (“power plant”)•Golgi apparatus – makes, packages and releases products inside/outside cell (“factories”)

Cell Organelles•Lysosome (animal only) – contain digestive enzymes. Breaks down and recycles substance (“garbage company”)

•Vacuoles – (mainly plants) store waste, food, pigments (“storage”)

More parts...Cytoplasm – gel-like mixture inside cell. Many chemicals are dissolved in it.

Nucleus - largest structure in the cytoplasm (“command center”)•Has a nuclear membrane (with pores – materials enter and leave the nucleus)•Contains chromosomes (made of DNA – deoxyribonucleic acid)

Plant Cells•Cell wall – rigid structure that provides support/protection for the cell

•Chloroplasts – contain chlorophyll – green pigment responsible for photosynthesis

Stem Cells

• Unspecialized: pluripotent or multipotent• Self-renewing• Give rise to mature, specialized cells

Sources: • Embryonic – cells from human blastocysts• Fetal – cells from aborted fetuses• Umbilical cord stem cells – cells from the umbilical cord of newborns• Placenta derived stem cells – cells from the placenta and amniotic fluid of

newborns• Adult – cells from adult tissue (bone marrow, fat...)

Example

• Adult stem cell found in bone marrow• red blood cells, white cells, platelets

http://www.csa.com/discoveryguides/stemcell/overview.php

Types of Stem Cells:

• Totipotent – each cell can develop into a new individual (cells from early embryos – 1-3 days)

• Pluripotent – cells can form any cell type (over 200) – some cells of blastocyst (5 to 14 days)

• Multipotent – cells differentiated, but can form other tissues – fetal tissue, cord blood, adult stem cells

ImportanceUse: • Cancer therapy: + 400,000 – leukemia, lymphoma, breast cancer, multiple myeloma• Bone marrow/immune regeneration: 2 million – autoimmune diseases, immunodeficiencies, solid organ transplants• Tissue repair/regeneration: 18 million – heart and vascular problems, diabetes, liver disease, arthritis, neurodegenerative

Potential Therapeutic Applications: • Cardiac – following heart damage• Nervous system – stroke/spinal cord, Parkinson’s, Alzheimer’s • Burns• Diabetes• Solid organ regeneration

Issues

• Embryo destruction: ethics/religion• Tissue rejection• Government funding• Uncontrolled cell division / misdirected

growth

http://www.youtube.com/watch?v=3Axkn8G18t8&feature=related