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Cells. Why are cells so tiny?. Larger cells do not function as efficiently The surface is the only way cells interact with the environment Surface-area-to-volume ratio As cell size increases, volume grows much more rapidly. Cell Theory. Schleiden and Schwann Three principles - PowerPoint PPT Presentation

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Page 1: Cells
Page 2: Cells

• Larger cells do not function as efficiently– The surface is the only way cells interact with the

environment– Surface-area-to-volume ratio• As cell size increases, volume grows much more rapidly

Why are cells so tiny?

Cell radius (r) Surface area (4πr2) Volume ((4/3)πr3)

1 units 12.57 units2 4.189 units3

10 units 1,257 units2 4,189 units3

Page 3: Cells

Cell Theory• Schleiden and Schwann• Three principles– All living things are composed of cells– Cells are the smallest living things (Functional units of the body)– Cells come from pre-existing cells

Page 4: Cells

• Prokaryotes – Lack a nucleus and

membrane bound organelles

– MUCH smaller than eukaryotes

– Bacteria

• Eukaryotes – Have a nucleus and

organelles– Much bigger than

prokaryotes

Cell Types

Page 5: Cells

• Cell membrane– Semi-permeable

• Cytoplasm— “cell blood”– Fluid matrix surrounding

nucleus– Surrounded by a cell

membrane• Nucleus— “cell brain”– Contains chromatin (loosely

coiled DNA)

Cell Organelles

Page 6: Cells

• Interconnected membranes forming canals and flattened sac-like spaces

• Functions:– Communications system– Rough ER: studded with

ribosomes • Involved in protein synthesis

– Smooth ER: has no ribosomes• Involved in synthesizing lipid

Endoplasmic reticulum

Page 7: Cells

• Composed of protein and RNA

• May be free in the cytoplasm or attached to ER

• Function:– Involved in protein

synthesis

Ribosomes

Page 8: Cells

• Stack of flattened membranes

• Function:– Package and transports

proteins from the cell

Golgi apparatus

Page 9: Cells

• “Cell powerhouse”• Contains its own DNA– Capable of self-reproduction

• Composed of 2 membranes• Contains enzymes used in cell

respiration• Function:– Produce ATP for cellular energy

(cell respiration)

Mitochondria

Page 10: Cells

• Small sacs from the Golgi apparatus

• Contains enzymes capable of breaking down breaking down nutrients or toxins

• Function:– Digestion

Lysosomes

Page 11: Cells

• Twin hollow cylinders (centrioles)

• Function:– Involved in cell division

Centriole

Page 12: Cells

• Tiny sacs formed by the cell membrane folding in and pinching off

• Function:– Intake or excretion of

large materials (endocytosis and exocytosis)

Vesicles

Page 13: Cells

• Tiny rods usually arranged in meshes or bundles

• Function:– Involved in cell

movement– Provides structure to

the cell

Microfilaments and

Microtubules

Page 14: Cells

• Fine, long, threadlike organelles protruding from the cell surface

• Function:– Cell movement

Cillia and Flagella

Page 15: Cells

nucleus

smooth ER

lysosomeGolgi

apparatus vesicles

centrosome

mitochondria

flagella

rough ER

Page 16: Cells

• Selectively permeable (semi-permeable)– Allows some substances in, excludes others

• Composed of phospholipid bilayer (containing cholesterol) and protein inclusions– Fat soluble molecules pass through the lipid part– Water soluble molecules must move through

protein component • Pores, channels or receptors

Cell Membrane

Page 17: Cells
Page 18: Cells

Passive Transport

• Movement of a material into or out of a cell without the use of energy.– Diffusion– Osmosis– Facilitated diffusion

– *** NO ENERGY REQUIRED***

Page 19: Cells

• The process by which molecules move down a concentration gradient– Move from area where there is more

concentration to areas that are less concentrated

– Rate limited by concentration

Diffusion

Page 20: Cells

• Diffusion using special carrier molecules to allow usually non-permeable molecules to pass through a selectively permeable membrane– Example: Insulin facilitates glucose movement

• Rate of passage is limited by the number of carrier molecules and concentration

Facilitated Diffusion

Page 21: Cells

• The diffusion of water through a selectively permeable membrane which may not allow dissolved substances to pass

• May result in changing volumes on either side of the membrane

• Osmotic pressure– The amount of pressure needed to stop osmosis

Osmosis

Page 22: Cells

• Hypertonic– A solution which has a greater concentration

of solute particles than a given cell or solution

• Hypotonic– A solution which has a lesser concentration

solute particles than a given cell or solution

• Isotonic– A solution which has an identical concentration

of solute particles to a given cell or solution

Concentration Types

Page 23: Cells

• The forcing of permeable molecules through a membrane by hydrostatic pressure– Example: Blood pressure

Filtration

Page 24: Cells

• The movement of molecules against a concentration gradient using cellular energy and carrier molecules– Proton pump– Sodium-potassium pump

Active Transport

***ENERGY REQUIRED***

Page 25: Cells

• Endocytosis– The inward movement of

molecules through a membrane by infolding and pinching off vesicles• Pinocytosis: taking in tiny

droplets of liquid• Phagocytosis: taking in solid

material• Receptor Mediated:

molecule bonds with receptor protein

• Exocytosis

Bulk Passage

Page 26: Cells

• Prokaryotes– Binary fision• DNA replicated in parent • Parent divides• Fast

• Eukaryotes– Mitosis• Complicated• Lots of DNA

– Form chromosomes (compact structures, composed of DNA and histone proteins, that can be manipulated easily during cell division

Cell division

Page 27: Cells

• Interphase– Period

“Inbetween” cell division

– Majority of cell’s life• Cell growth• Protein synthesis

Cell cycle

Page 28: Cells

• Cell division that Is Mighty Common

• Makes all cells EXCEPT gametes (reproductive cells)

• DNA is doubled then– Cells divide once

Mitosis

Page 29: Cells

• Cells Prepares to divide

• Chromatin condenses into chromosomes

• Nuclear membrane disappears

Prophase

Page 30: Cells

• Chromosomes line up in the Middle

• Spindle Apparatus stretches from pole to pole

Metaphase

Page 31: Cells

• Sister chromatids move Away to opposite poles

Anaphase

Page 32: Cells

• Cell “Tears” in two• Nuclear membrane reforms• Chromosomes disperse into

chromatin• Cytokinesis (cytoplasmic

division) (separate phase?) – Produces 2 identical “daughter

cells”

Telophase

Page 33: Cells

• Process by which cells develop different characteristics in structure and function

• Differences in outcome– Directed by cell’s DNA– Determined by cell’s

position in the body and its chemical environment

Cell differentiati

on

Page 34: Cells