Cellular Functions

• Chapter 1– The Cell Theory– Cell Structure– Organelles– Animal and Plant Cells

• Chapter 2– Nutrients– Nucleic Acids– Cell Membrane– Transport– Respiration and Photosynthesis

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• Biology is a natural science concerned with the study of life and living organisms, including their:– Structure, – Function, – Growth,– Evolution,– Distribution and – Taxonomy

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http://en.wikipedia.org/wiki/Biology

• Biology as a Science progressed by observation.

• The hypotheses proposed by early scientists were rarely tested by experiments.

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• Abiogenesis is the belief that living organisms can be created, or arise, from non living matter.

• Many abiogenesis hypothesis proposed by scientists were rarely tested by experiments.

• For Example:– Pond dries up – no fish or frogs– Rain comes – fish and frogs

Therefore: It rained fish and frogs

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• Proposed by Aristotle who observed rotting meat and flies.

• People Believed this for 2000 years!

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• Biogenesis is the principle that living organisms develop from other living organisms and not from non living matter.

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• There were a number of important Scientists who contributed to the theory of Abiogenesis and Biogenesis. Some of these include:

– Jean Van Helmont– Francesco Redi– John Needham– Lazzaro Spallanzani– Louis Pasteur

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• ~300 years ago

Belgian doctor Jean van Helmont – concluded that mice could be created from a dirty shirt.

• He placed grains of wheat and a dirty shirt in a container and in 21 days mice appeared.

• Conclusion: Sweat caused wheat to ferment into mice. Abiogenesis!

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• In 1668 Francesco Redi (Italian physician) tested Aristotle’s hypothesis (meat flies)

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• 4 sets of jars with meat (snake, eel, fish, veal)

one set was open (experimental group)

one set was sealed (control group)

• Maggots appeared on open jars of meat

• Conclusion: Flies come from flies!

• Biogenesis – life from life.

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• John Needham (1713 – 1781) English botanist

• Reexamined theory of Abiogenesis

• Observed meat broth left unsealed soon changed colour (evidence of microorganisms).

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Experiment:

• Boiled flasks of meat broth to kill microorganisms

• Left the flasks unsealed!

• Flasks soon become murky and full of microbes

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Conclusion:

• Abiogenesis

• This conclusion sent many scientists down the wrong path.

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• 25 years later Spallanzani repeated experiment more carefully

• Boiled flasks longer and sealed flasks

• Critics again objected to sealed flasks!

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• Louis Pasteur (1822-1895)

• Developed the swan neck flask in 1864

• This led to great scientific break through!

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Experiment:

• Boiled broth, air could enter but microbes were trapped in curved flask

• Broth remained clear Biogenesis finally proven!

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Unit 1 Chapter 1

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• All living things are composed of one or more cells.

• The cell is the basic unit of structure and function of all living things.

• All cells arise only from pre-existing cells.

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• What is a prokaryotic cell?

– Prokaryotes and unicellular organisms that lack a nucleus and membrane bound organelles.

– These are the most simple types of living cells.

– Examples: cyanobacteria, E.Coli

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• Eukaryote cells do have a nucleus and membrane bound organelles.

• Eukaryotes can be multicellular– organisms made of many cells

OR

• Eukaryotes can be unicellular– organisms made only of one cell

• Plants, Animals, Fungus and Protists are all eukaryotes.

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• Within cells there is an intricate network of organelles that all have unique functions.

• These organelles allow the cell to function properly.

• Here is a description of common organelles and their location.

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• Nucleus– One or more per cell

-- Control center of the cell– Spherical shape– Denser than surrounding cytoplasm

-- made of DNA (deoxyribonucleic acid)

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Chromosome-Usually in the form of chromatin-Contains genetic information-Composed of DNA-Thicken for cellular division-Set number per species (i.e. 23 pairs for human)

• Nuclear membrane– Surrounds nucleus– Composed of two layers– Numerous openings (pores) for nuclear traffic

• Nucleolus– Spherical shape– Visible when cell is not dividing– Contains RNA for protein manufacture– Makes ribosomes

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• Endoplasmic reticulum– Tubular network fused to nuclear membrane– Goes through cytoplasm onto cell membrane– Stores, separates, and serves as cell's transport system– Smooth type: lacks ribosomes– Rough type (pictured): ribosomes embedded in surface

• Golgi Apparatus– Protein 'packaging plant‘– A membrane structure found near nucleus– Composed of numerous layers forming a sac

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• Ribosomes– Each cell contains thousands– Miniature 'protein factories‘– Composes 25% of cell's mass– Stationary type: embedded in rough endoplasmic

reticulum– Mobile type: injects proteins directly into cytoplasm

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• Cytoplasm– Collective term for cytosol and organelles contained

within– Colloidal suspension– Cytosol mainly composed of water with free-floating

molecules– Viscosity constantly changes

• Centrioles– Paired cylindrical organelles near nucleus– Composed of nine tubes, each with three tubules– Involved in cellular division– Lie at right angles to each other

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• Chloroplasts– A plastid usually found in plant cells– Contain green chlorophyll where

photosynthesis takes place

• Cytoskeleton– Composed of microtubules– Supports cell and provides shape– Aids movement of materials in and out of cells

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Microfilaments Microtubules Cytoskeleton

Mitochondira– Second largest organelle with

unique genetic structure– Double-layered outer membrane with inner folds

called cristae– Energy-producing chemical reactions take place

on cristae– Controls level of water and other materials in cell– Recycles and decomposes proteins, fats, and

carbohydrates, and forms urea

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• Lysosome– Digestive 'plant' for proteins, lipids, and

carbohydrates– Transports undigested material to cell membrane

for removal– Vary in shape depending on process being

carried out– Cell breaks down if lysosome explodes

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Vacuoles-Membrane-bound sacs for storage, digestion, and waste removal-Contains water solution-Contractile vacuoles for water removal (in unicellular organisms)

• Cell Wall– Most commonly found in plant cells– Controls turgity– Extracellular structure surrounding plasma

membrane– Primary cell wall: extremely elastic– Secondary cell wall: forms around primary cell

wall after growth is complete

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Plasma membrane-Outer membrane of cell that controls cellular traffic-Contains proteins (left, gray) that span through the membrane and allow passage of materials-Proteins are surrounded by a phospholipid bi-layer.

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Plant Cells Animal Cells

Have chloroplasts and cell Walls

Do Not have chloroplasts and cell

walls

Do not usually have centrioles

Have centrioles

Have a large central vacuole

Do Not have a large central vacuole

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Video

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