Ch. 6 Warm-Up What are the 2 main types of cells? Which Domains do they consist of? List 3 ways that eukaryotes differ from prokaryotes.

Ch. 6 Warm-Up How is the size of a cell related to its function? Name 5 organelles or cell structures and their function.

Pick up handout on back counter. Warm-Up Activity: Pick up handout on back counter. Complete this handout for your warm-up activity.

Compare and contrast Animal vs. Plant Cells Animal Cell Plant Cell Ch. 6 Warm-Up Compare and contrast Animal vs. Plant Cells Animal Cell Plant Cell

Ch. 6 Warm-Up What is the structure & function of: Microtubules Microfilaments Intermediate filaments

Ch. 6 Warm-Up What is the function of: Plasmodesmata Gap junctions Tight junctions Desmosomes

Chapter 6 A Tour of the Cell

Three differences between prokaryotic and eukaryotic cells. You Must Know Three differences between prokaryotic and eukaryotic cells. The structure and function of organelles common to plant and animal cells. The structure and function of organelles found only in plant cells or only in animal cells.

How We Study Cells Biologists use microscopes and the tools of biochemistry to study cells

Size range of cells Note that light microscopes can not magnify as well as electron microscopes

Light Microscopy (LM) vs. Electron Microscopy (EM)

Cell Size and Scale http://learn.genetics.utah.edu/content/begin/cells/scale/ Scale of the Universe: http://www.onemorelevel.com/game/scale_of_the_unive rse_2012

Cells must be small to maintain a large surface area to volume ratio Large S.A. allows  rates of chemical exchange between cell and environment

Limits to cell size Metabolic requirements set upper limit aa aa aa aa in large cell, cannot move material in & out of cell fast enough to support life aa aa What process is this? CH NH3 aa CHO O2 CH CHO CO2 CHO CO2 CO2 What process is this? diffusion What’s the solution? cell divides make a multi-celled creature = lots of little cell, rather than one BIG cell aa NH3 O2 NH3 O2 CHO NH3 aa CO2 CH aa CH O2 aa O2 2005-2006 What’s the solution?

How to get bigger? aa aa aa O2 aa aa aa Become multi-cellular (cell divides) But what challenges do you have to solve now? CO2 CO2 O2 NH3 aa NH3 aa CO2 NH3 O2 CO2 CO2 CH CHO CO2 NH3 Larger organisms do not generally have larger cells than smaller organisms — simply more cells What’s challenges do you have to solve now? how to bathe all cells in fluid that brings nutrients to each & removes wastes from each aa O2 NH3 NH3 CO2 CO2 CO2 CHO aa NH3 NH3 NH3 CH CHO CO2 CO2 O2 aa aa CH 2005-2006

Surface Area Example (Animal): Small Intestine: highly folded surface to increase absorption of nutrients Villi: finger-like projections on SI wall Microvilli: projections on each cell

Folds  Villi  Microvilli

Surface Area Example (Plant): Root hairs: extensions of root epidermal cells; increase surface area for absorbing water and minerals

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

2 Types of Cells: Prokaryotes: Domain Bacteria & Archaea Eukaryotes (Domain Eukarya): Protists, Fungi, Plants, Animals

A Prokaryotic Cell (bacteria)

Prokaryote Vs. Eukaryote “before” “kernel” No nucleus DNA in a nucleoid Cytosol No organelles other than ribosomes Small size Primitive i.e. Bacteria & Archaea “true” “kernel” Has nucleus and nuclear envelope Cytosol Membrane-bound organelles with specialized structure/function Much larger in size More complex i.e. plant/animal cell

Why organelles? Specialized structures specialized functions mitochondria Specialized structures specialized functions cilia or flagella for locomotion Containers partition cell into compartments create different local environments separate pH, or concentration of materials distinct & incompatible functions lysosome & its digestive enzymes Membranes as sites for chemical reactions unique combinations of lipids & proteins embedded enzymes & reaction centers chloroplasts & mitochondria chloroplast Golgi Why organelles? There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions. Organelles as specialized structures An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move. Organelles as Containers Nothing ever invented by man is as complex as a living cell. At any one time hundreds of incompatible chemical reactions may be occurring in a cell. If the cell contained a uniform mixture of all the chemicals it would not be able to survive. Organelles surrounded by membranes act as individual compartments for these chemical reactions. An example of the second type of organelle is the lysosome. This structure contains digestive enzymes, these enzymes if allowed to float free in the cell would kill it. Organelle membranes as sites for chemical reactions An example of the third type of organelle is the chloroplast. The molecules that conduct the light reactions of photosynthesis are found embedded in the membranes of the chloroplast. ER

Nucleus Function: control center of cell Contains DNA Surrounded by double membrane (nuclear envelope) Continuous with the rough ER Nuclear pores: control what enters/leaves nucleus Chromatin: complex of DNA + proteins; makes up chromosomes Nucleolus: region where ribosomal subunits are formed

Nucleus Contains DNA Function: control center of cell Surrounded by double membrane (nuclear envelope) Continuous with the rough ER Nuclear pores: control what enters/leaves nucleus Chromatin: complex of DNA + proteins; makes up chromosomes Nucleolus: region where ribosomal subunits are formed

Ribosomes Function: protein synthesis Composed of rRNA + protein Large subunit + small subunit Types: Free ribosomes: float in cytosol, produce proteins used within cell Bound ribosomes: attached to ER, make proteins for export from cell

Endomembrane System: Regulates protein traffic & performs metabolic functions

Endoplasmic Reticulum (ER) Network of membranes and sacs Types: Rough ER: ribosomes on surface Function: package proteins for secretion, send transport vesicles to Golgi, make replacement membrane Smooth ER: no ribosomes on surface Function: synthesize lipids, metabolize carbs, detox drugs & poisons, store Ca2+

Endoplasmic Reticulum (ER)

Golgi Apparatus Function: synthesis & packaging of materials (small molecules) for transport (in vesicles); produce lysosomes Series of flattened membrane sacs (cisternae) Cis face: receives vesicles Trans face: ships vesicles

Lysosomes Function: intracellular digestion; recycle cell’s materials; programmed cell death (apoptosis) Contains hydrolytic enzymes

Vacuoles Function: storage of materials (food, water, minerals, pigments, poisons) Membrane-bound vesicles Eg. food vacuoles, contractile vacuoles Plants: large central vacuole -- stores water, ions

Parts of plant & animal cell p 108-109

Mitochondria Function: site of cellular respiration Double membrane: outer and inner membrane Cristae: folds of inner membrane; contains enzymes for ATP production; increased surface area to  ATP made Matrix: fluid-filled inner compartment

Chloroplasts Function: site of photosynthesis Double membrane Thylakoid disks in stacks (grana); stroma (fluid) Contains chlorophylls (pigments) for capturing sunlight energy

Endosymbiont theory Mitochondria & chloroplasts share similar origin Prokaryotic cells engulfed by ancestors of eukaryotic cells Evidence: Double-membrane structure Have own ribosomes & DNA Reproduce independently within cell

Peroxisomes Functions: break down fatty acids; detox alcohol Involves production of hydrogen peroxide (H2O2)

Cytoskeleton: network of protein fibers Function: support, motility, regulate biochemical activities

Extracellular Matrix (ECM) Outside plasma membrane Composed of glycoproteins (ex. collagen) Function: Strengthens tissues and transmits external signals to cell

Intercellular Junctions (Animal cells) Tight junctions: 2 cells are fused to form watertight seal Desmosomes: “rivets” that fasten cells into strong sheets Gap junctions: channels through which ions, sugar, small molecules can pass

Plant Cells Cell wall: protect plant, maintain shape Composed of cellulose Plasmodesmata: channels between cells to allow passage of molecules

Plant Cells Only Animals Cells Only Central vacuoles Lysosomes Chloroplasts Centrioles Cell wall of cellulose Flagella, cilia Plasmodesmata Desmosomes, tight and gap junctions Extracellular matrix (ECM)

Harvard cell video http://multimedia.mcb.harvard.edu/anim_innerlife .html