The cell. The cell theory. So what is a cell? 9/20/2010. Chapter 3

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Erica Patterson
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1 The cell Chapter 3 The cell theory all living organisms are made up of one or more cells, and all cells arise from other, pre-existing cells So what is a cell? The most basic unit of any organism The smallest unit of life that can perform all the necessary functions of life A three-dimensional structure where the essential chemical reactions of life take place All cells have: plasma membrane encompasses the cell cytoplasm the jelly-like fluid that fills the inside of the cell ribosomes cellular structures where proteins are made DNA Only two kinds of cells prokaryotic eukaryotic 1

Characteristics of prokaryotic cells No nucleus No membrane-bound

capsule for protection & adhesion pili: hair-like projections to

locomotion Only single celled organisms bacteria & archaea

prokaryotic cells Nucleus & other membranebound organelles with

simultaneously DNA is linear Single celled organisms protists

2 Characteristics of prokaryotic cells No nucleus No membrane-bound organelles DNA is circular Rigid cell wall Some have: sticky capsule for protection & adhesion pili: hair-like projections to help attach to surfaces flagellum: long, thin, whip-like tail for locomotion Only single celled organisms bacteria & archaea Characteristics of eukaryotic cells Larger & more complex than prokaryotic cells Nucleus & other membranebound organelles with specific functions allows different chemical reactions to occur simultaneously DNA is linear Single celled organisms protists Multicellular organisms animals, plants & fungi Two kinds of eukaryotic cells Animal cells Plant cells 2

Differences b/w plant & animal cells Animal cells have lysosomes centrioles some

chloroplasts central vacuole What cells do... they re busy!

stuff lysosomes & vacuoles Process energy mitochondria & chloroplasts Maintain

membrane & cell wall Cell parts: plasma membrane Made of a phospholipid bilayer

3 Differences b/w plant & animal cells Animal cells have lysosomes centrioles some have flagella or cilia Plant cells have cell wall with plasmodesmata chloroplasts central vacuole What cells do... they re busy! Manufacture & package stuff nucleus, ribosomes, ER & Golgi apparatus Breakdown stuff lysosomes & vacuoles Process energy mitochondria & chloroplasts Maintain structural support, movement & communication systems cytoskeleton, plasma membrane & cell wall Cell parts: plasma membrane Made of a phospholipid bilayer Separates the inside of the cell (cytoplasm) from outside environment Controls what molecules move into or out of the cell 3

Embedded molecules of the plasma membrane Carbohydrates: help with cell to cell recognition Lipids (cholesterol): helps membrane remain flexible

membrane proteins There are many, but the main four types are: 1 2 3 4 Movement of molecules across the plasma membrane Passive transport

4 Embedded molecules of the plasma membrane Carbohydrates: help with cell to cell recognition Lipids (cholesterol): helps membrane remain flexible without becoming too loose or too rigid only in animal cells Proteins surface or transmembrane tertiary structure determines location Plasma membrane proteins There are many, but the main four types are: Movement of molecules across the plasma membrane Passive transport molecules move down a concentration gradient requires no cellular energy Active transport molecules move against concentration gradient requires cellular energy 4

Passive transport Simple diffusion small molecules without any charge pass right through the membrane

diffusion of water to equalize the amount of water on both sides of a membrane hypertonic hypotonic

Requires use of transport protein Moving large molecules across a plasma membrane Exocytosis

5 Passive transport Simple diffusion small molecules without any charge pass right through the membrane Facilitated diffusion polar or larger molecules need the help of a transport protein Osmosis diffusion of water to equalize the amount of water on both sides of a membrane hypertonic hypotonic isotonic Active transport Molecules move against concentration gradient Requires cellular energy! Requires use of transport protein Moving large molecules across a plasma membrane Exocytosis exporting material Endocytosis importing material phagocytosis pinocytosis receptor-mediated Both require cellular energy! 5

6 Exocytosis Endocytosis Endocytosis, cont. White blood cell engulfing a yeast cell An amoeba showing pinocytosis 6

Intercellular junctions, animal cells Allows for cell to cell communication and to adhere to each other Intercellular junctions, plant

herbivory have plasmodesmata channels that allow for communication and transport of material between cells A few important organelles

information structure nuclear membrane made of TWO phospholipid bilayers with pores to allow passages of materials inside has chromatin,

7 Intercellular junctions, animal cells Allows for cell to cell communication and to adhere to each other Intercellular junctions, plant cells Cell walls surround the plasma membrane made of cellulose allows plant to grow tall helps prevent water loss helps protect from herbivory have plasmodesmata channels that allow for communication and transport of material between cells A few important organelles Nucleus, the largest organelle functions controls most cellular activities by directing the production of molecules stores genetic information structure nuclear membrane made of TWO phospholipid bilayers with pores to allow passages of materials inside has chromatin, long thin strands of DNA & associated proteins inside has nucleolus where ribosomes are assembled Ribosomes are the site of protein synthesis in the cytoplasm 7

A few important organelles Mitochondria makes energy molecule ATP to fuel cellular work site of

(an inner & outer) contains circular DNA with instructions for making proteins necessary for

chemical energy site of photosynthesis two membranes similar in structure to mitochondria

little organ membrane bound There are important cellular structures that are not true

8 A few important organelles Mitochondria makes energy molecule ATP to fuel cellular work site of cellular respiration found in nearly every eukaryotic cell; #s vary by cell type two membranes (an inner & outer) contains circular DNA with instructions for making proteins necessary for energy conversion A few important organelles Chloroplasts; in plants converts light energy into chemical energy site of photosynthesis two membranes similar in structure to mitochondria contains circular DNA with genes essential for photosynthesis Remember what an organelle is little organ membrane bound There are important cellular structures that are not true organelles ribosomes centrioles (in animal cells) cytoskeleton How did organelles get inside the eukaryotic cell? 8

Endosymbiosis theory Mitochondria & chloroplasts were once small prokaryotes that began living in larger prokaryotes may have been undigested prey or parasites Over time, the endosymbiont & the host

9 Endosymbiosis theory Mitochondria & chloroplasts were once small prokaryotes that began living in larger prokaryotes may have been undigested prey or parasites Over time, the endosymbiont & the host both benefited from the relationship Eventually, they grew increasingly dependent on each other until they could not live w/o each other became a single, more complex organism Mitochondria & chloroplasts are different from other organelles Both are similar in size to prokaryotes Both are surrounded by a double membrane inner membrane has many similarities to prokaryotic membranes Both contain their own DNA DNA is circular like prokaryotic DNA Both contain their own ribosomes more similar to prokaryotic ribosomes than to eukaryotic ribosomes Both reproduce by a splitting process similar to some prokaryotes 9

Cellular Biology. Cells: theory, types, form & function, evolution

Cellular Biology. Cells: theory, types, form & function, evolution Cellular Biology Cells: theory, types, form & function, evolution The Cell Theory Problems with the Cell Theory? The cell theory has three components: 1. all living organisms are made up of one or more