Topics 2.1, 2.2 and 2.3

Cells

IB Biology I

LifePossible origins:

Extraterrestrial Supernatural Chemical Evolution (inorganic → organic → cells)

Requirements for life: C, H, O, N, P, S Sunlight/chemical energy UV radiation protection Gravity 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 DiscoveryLinked to microscope development

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

Two main types: light and electron

Light MicroscopeLight passes through an object and 2 or more lensesPossible 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 MicroscopeTwo 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

TimelineAnton 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)

TimelineRobert 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

TimelineMathias 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 timeResponse: sense environmentHomeostasis: regulate/balance reactions in the body according to the environment conditionsGrowth: production of new organellesReproduction: division Nutrition: release energy from food

Amoeba Paramecium

Multicellular Organisms

InteractionCommunicationCells 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 sizeRate of heat production/waste/resource consumption – volumeRate or exchange material/energy – surface areaAs cell size increases, the surface area to volume ratio decreasesMetabolic 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.

The Metric SystemKnow how to convert from one unit to another.

Basic Unit

Kilo-1000Units

Hecto-100 units

Deka-10

unitsDeci-0.1

unitsCenti-0.01 units

Milli-0.001units

Multiply

Divide

What units are used to measure cells?

1 mm = 1000 micrometers (um)1 mm = 1,000,000 nanometers (nm)Or…

A micrometer is 1 x 10-3 mm (0. 001) A nanometer is 1 x 10-6 mm (0.000001 mm)

Calculating Linear Magnification

What is the actual size of this specimen in um?60mm/5 = 12mm12mm x 1000 um =

12,000 um

60 mm

Measuring picture

Magnification x 5

Cell OrganizationCells differ:SizeShape

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

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

Cell MembraneOuter boundary: phospholipid bilayerCommunication between cellsSelects 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 OrganellesMitochondria – produce ATP (“power plant”)Golgi apparatus – makes, packages and releases products inside/outside cell (“factories”)

Cell OrganellesLysosome (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 CellsCell 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: hematopoietic rare – have markers 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