The Cell Essential Knowledge As cells increase in

The Cell

Essential Knowledge: § As cells increase in volume, the surface area § decreases and demand for material resources increases (more cellular structures are necessary to adequately exchange materials and energy with the environment). These limitations restrict cell size The surface area of the plasma membrane must be large enough to adequately exchange materials; smaller cells have a more favorable surface area-to-volume ratio for exchange of materials with the environment.

CELL THEORY § All organisms are made of one or more cells. § Cells are the basic unit of structure and § function in living things Cells arise by division of pre- existing cells.

Why are cells so small? Why can’t they be as huge as an hippo?

What limits cell size? § Surface to volume ratio u as cell gets bigger its volume increases faster than its surface area § smaller objects have greater ratio of surface area to volume What cell organelle governs this? Why is a huge single-celled creature not possible? s: v 6: 1 2005 -2006 6: 1 ~1: 1

Limits to cell size § Metabolic requirements set upper limit in large cell, cannot move material in & out of cell fast enough to support life aa aa What process is this? CH NH 3 aa u O 2 CH aa CHO CO 2 CHO CH aa aa O 2 CHO NH 3 O 2 NH 3 CHO O 2 CO 2 NH 3 CH 2005 -2006 aa What’s the solution?

How to get bigger? § Become multi-cellular (cell divides) But what challenges do you have to solve now? CO 2 aa O 2 CH aa NH 3 CO 2 CHO NH 3 CHO CH O 2 aa aa O 2 aa CH NH 3 CO 2 NH 3 O 2 NH 3 CO 2 aa CHO 2005 -2006

Check for Understanding § Cell Surface Area Activity

Essential Knowledge § Organelles in eukaryotic cells compartmentalize § metabolic processes and specific reactions. You will need to be able to explain how internal membranes and organelles contribute to cell functions. u E. R, mitochondria, chloroplasts, nucleus, etc. Bacteria generally lack organelles. You will need to use models to describe differences in prokaryotic and eukaryotic cells.

Cell characteristics § All cells: surrounded by a plasma membrane u have cytosol u § semi-fluid substance within the membrane § cytoplasm = cytosol + organelles contain chromosomes which have genes in the form of DNA u have ribosomes u § tiny “organelles” that make proteins using instructions contained in genes

Types of cells Prokaryote bacteria cells - no organelles - organelles Eukaryote animal cells Eukaryote plant cells

Types of cells § Prokaryotic vs. eukaryotic cells Prokaryotic cell § DNA in nucleoid region, without a membrane separating it from rest of cell § Cell wall present in all (type differs) Eukaryotic cell § chromosomes in nucleus, membraneenclosed organelle § Cell walls present in fungi and plants only § More complex § Membrane bound organelles present

The prokaryotic cell is much simpler in structure, lacking a nucleus and the other 2005 -2006 membrane-enclosed organelles of the eukaryotic cell.

Why organelles? § Specialized structures u specialized functions mitochondria § cilia or flagella for locomotion § Containers u u partition cell into compartments create different local environments chloroplast § separate p. H, or concentration of materials u distinct & incompatible functions § lysosome & its digestive enzymes § Membranes as sites for chemical reactions u u unique combinations of lipids & proteins embedded enzymes & reaction centers Golgi § chloroplasts & mitochondria ER

Cells gotta work to live! § What jobs do cells have to do? u make proteins § proteins control every cell function u make energy § for daily life § for growth u make more cells § growth § repair § renewal

Building Proteins § Organelles involved nucleus u ribosomes u endoplasmic reticulum (ER) u Golgi apparatus u vesicles u The Protein Assembly Line nucleus ribosome ER Golgi apparatus vesicles

Synthesizing proteins cisternal space polypeptide signal sequence ribosome m. RNA membrane of endoplasmic reticulum cytoplasm

Nucleolus § Function u ribosome production § build ribosome subunits from r. RNA & proteins § exit through nuclear pores to cytoplasm & combine to form functional ribosomes large subunit small subunit r. RNA & proteins ribosome nucleolus

Types of Ribosomes § Free ribosomes u u suspended in cytosol synthesize proteins that function in cytosol § Bound ribosomes u u attached to endoplasmic reticulum synthesize proteins for export or for membranes membrane proteins

Rough ER function § Finalize protein formation and prepare for export out of cell (protein folding) u protein secreting cells will have lots u packaged into transport vesicles to golgi Which cells have lot of rough ER?

Golgi Apparatus § Function u finishes, sorts, tags & ships cell products § like “UPS shipping department” u Which cells have lots of Golgi? ships products in vesicles § membrane sacs § “UPS trucks” secretory vesicles transport vesicles

Putting it together… nucleus nuclear pore Making proteins cell membrane protein secreted rough ER ribosome vesicle proteins smooth ER transport vesicle cytoplasm Golgi apparatus

Smooth ER function § Membrane production § Many metabolic processes u synthesis § synthesize lipids w oils, phospholipids, steroids & sex hormones u hydrolysis § hydrolyze glycogen into glucose w in liver § detoxify drugs & poisons w in liver w ex. alcohol & barbiturates

Where old organelles go to die! Lysosomes § Function u little “stomach” of the cell § digests macromolecules u “clean up crew” of the cell § cleans up broken down organelles § Structure u vesicles of digestive enzymes synthesized by r. ER, transferred to Golgi only in animal cells

Cellular digestion § Lysosomes fuse with food vacuoles u polymers digested into monomers § pass to cytosol to become nutrients of cell vacuole § lyso– = breaking things apart § –some = body

When cells need to die… § Lysosomes can be used to kill cells when they are supposed to be destroyed u some cells have to die for proper development in an organism § apoptosis w “auto-destruct” process w lysosomes break open & kill cell § ex: tadpole tail gets re-absorbed when it turns into a frog § ex: loss of webbing between your fingers during fetal development

Fetal development syndactyly 6 weeks 15 weeks

Food & water storage food vacuoles plant cells central vacuole animal cells contractile vacuole

Vacuoles & vesicles § Function u little “transfer ships” § Food vacuoles w phagocytosis, fuse with lysosomes § Contractile vacuoles w in freshwater protists, pump excess H 2 O out of cell § Central vacuoles w in many mature plant cells

Vacuoles in plants § Functions u storage stockpiling proteins or inorganic ions depositing metabolic byproducts storing pigments storing defensive compounds against herbivores § selective membrane w control what comes § § in or goes out�

Making Energy § Cells must convert incoming energy to forms that they can use for work mitochondria: ATP from glucose to ATP u chloroplasts: from sunlight to ATP & carbohydrates u § ATP = active energy § carbohydrates = stored energy ATP +

Mitochondria & Chloroplasts § Important to see the similarities u transform energy § generate ATP double membranes = 2 membranes u semi-autonomous organelles u § move, change shape, divide u internal ribosomes, DNA & enzymes

Mitochondria § Function cellular respiration u generate ATP u § from breakdown of sugars, fats & other fuels - catabolism § generate energy in presence of O 2 = aerobic respiration § Semi-autonomous – can replicate itself

Mitochondria § Almost all eukaryotic cells have mitochondria u number of mitochondria is correlated with aerobic metabolic activity § more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria? active cells: • muscle cells • nerve cells

Chloroplasts § Chloroplasts are plant organelles u class of plant structures = plastids § chromoplasts w store pigments for fruits & flowers § chloroplasts w store chlorophyll & function in photosynthesis w in leaves, other green structures of plants & in eukaryotic algae

Chloroplasts § Function photosynthesis u generate ATP & synthesize sugars u § transform solar energy into chemical energy § produce sugars from CO 2 & H 2 O § Semi-autonomous § moving, changing shape & dividing § can reproduce by pinching in two Who else divides like that? bacteria!

Mitochondria & chloroplasts are different from other organelles…how? § Not part of endomembrane system It’s the set of membranes that form a single functional and developmental unit, either being connected directly, or exchanging material through vesicle transport Grow & reproduce Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes Own circular chromosome u directs synthesis of proteins produced by own internal ribosomes § ribosomes like bacterial ribosomes u § § § Who else has a circular chromosome not bound within a nucleus? bacteria

Endosymbiosis theory 1981 § Mitochondria & chloroplasts were once free living bacteria u engulfed by ancestral eukaryote § Endosymbiont u cell that lives within another cell (host) § mutualistic relationship § evolutionary advantage for both w one supplies energy w the other supplies raw materials & protection Lynn Margulis U of M, Amherst

Endosymbiosis theory Evolution of eukaryotes

Putting it all together, try labeling. . animal cells plant cells

Any Questions? ? 2007 -2008