CH. 3 ~ CELLS

Robert Hooke 1665 Looked at thin slices of cork under a microscope Did not know at the time about their structure and function. What IS a cell?

A cell is the smallest unit of life that can carry out all the activities necessary for life. 1670’s Van Leeuwenhoek….hand lens

THE CELL THEORY One of the foundations of modern biology. It states: 1.All living things are made up of one or more cells 2.Cells are the most basic unit of structure and function in an organism 3.Cells originate only from pre-existing cells 4. Energy Flow (metabolism) occurs within cells; must maintain an internal balance (homeostasis) 5. Cells contain DNA (hereditary information) -reproduce. Schleiden + Schwann + Virchow

VIRCHOW “Omnis cellula e cellula” 1855: New cells arise from pre-existing cells Tremendous controversy….against the prevailing theory at the time “Spontaneous Generation” aka Vitalism Ponds dry up…..teeming with life again Rotting meats ‘spontaneously’ give rise to maggots

“Spontaneous Generation” (Life evolves from non-life) (Francesco Redi 1688)

Spallanzani 1700’S Still did not believe….Blocking the “vital force”….. Who ultimately disproved spontaneous generation?

PASTEUR 1860’S

TYPES OF CELLS

1 meter = 1000 millimeters (mm) 1 mm = 1000 micrometers (um) 1 um = 1000 nanometers (nm) Cell Size

Why are cells so different? Specialized Functions! 1m

What Limits the Size of a Cell? Human Body consists of about 100 trillion cells (A string 100 trillion inches long could be wrapped around Earth more than 63,000 times) Cell grows- needs to take in food and get rid of waste through the cell membrane. Cell cannot grow so large that their surface area becomes too small to take in enough food and remove enough wastes Cells volume increases faster than its surface area. Surface area = 6s 2 Volume = l x w x h

DEFINITIONS/DESCRIPTIONPROKARYOTIC CELL EUKARYOTIC CELL SIZEVery small.2-10 um Varies, generally much larger um ORGANISMSBacteria, cyanobacteriaPlants, animals and fungi CILIA AND FLAGELLAYes (pili)Yes CELL WALLYes Yes (Plants and Fungi) No (Animals) PLAMA (CELL) MEMBRANEYes CYTOPLASMYes CHROMOSOMES, DNA Strand of DNA (nuceloid,plasmid) Yes RIBOSOMESYes MEMBRANE BOUND ORGANELLES NoYes

Every bacterial cell – Eubacteria – Archeabacteria Every organisms that is not bacteria: Animals – Plants – Fungus - Protists

Inner Life of the Cell Animation 3.12

Cell Membrane Surrounds ALL cells Semi-permeable – Selective; only allows certain substances to pass through Contains proteins that help to pass materials through, for identification, anchoring. “Phospholipid bilayer” Flexible and “fluid”

Cytosol/Cytoplasm Semi fluid portion of the cell; contains the organelles and allows reaction to occur Composed mostly of water and plays a role in diffusion of materials across the cell membrane. Amoeba Cytoplasmic Streaming 1.52Elodea Cytoplasmic Streaming 1.12

Nucleus Membrane-bound organelle; Surrounded by the nuclear envelope aka membrane Found only in Eukaryotes Controls the cell functions and processes Contains DNA that directs the formation of necessary proteins. (genetic blueprint)

Nucleolus An organelle within the nucleus that produces ribosomes and RNA

Ribosomes small organelles that are sites of protein synthesis Made by the nucleolus Take information from the DNA (delivered to the ribosome by RNA) and use it to make protein Sometimes found on the ER (or the rough endoplasmic reticulum), but also found in the cytoplasm of ALL cells

Endoplasmic reticulum (ER) – detoxification and transport; works closely with the golgi apparatus Attached to the nuclear membrane and zigzags through the cell Rough or smooth – Rough = has ribosomes *protein synthesis & folding – Smooth = no ribosomes *Lipids/detox

Golgi Apparatus (Bodies) Packaging and distribution “UPS center” Flattened, layered, sac-like organelles which are located near the nucleus. Works w/ ER….receives proteins, lipids- modifies and packages into vesicles for transport to: – Lysomes – Plasma membrane – Other organelles

TRANSPORTTRANSPORT lysosome ER and Golgi

MITOCHONDRIA “Powerhouse” of the cell Converts food into energy (ATP) (Site of cellular respiration) Inner and outer membrane Has it’s own DNA (endosymbiotic theory) Found in Eukaryotes Only

VACUOLE Contains water (Can also store nutrients, waste products) Large in plants, small in animals Controls “turgor pressure” in plants.

Lysosomes Contain hydrolytic enzymes to break down old organelles (may also play a role in programmed cell death….apoptosis) Centrioles Only in animals cells. Two structures near the nucleus, give rise to the spindle apparatus needed for cell reproduction. 9/3 Triplet Microtubule arrangement Peroxisomes Contain enzymes (catalase) that produce (for detox purposes) or degrade (if needed- so not released into the cell) hydrogen peroxide

Flagella – long whip-like tail for movement Cilia – short hairs for movement Microtubule “9 + 2” arrangement

PLANT CELL

CHLOROPLASTS Converts sunlight, water and carbon dioxide to sugar and oxygen through photosynthesis – Has chlorophyll – pigment that captures the sun’s light. Inner and outer membrane Found in Eukaryotes only Found only in plants (producers/autotrophs)

Cell Wall A rigid structure found on the outside of plant, fungal and bacterial cells Permeable – allows most substances to enter freely Composed of cellulose and protein Located OUTSIDE of the cell membrane Structure relates to function: – The rigid structure of the cell wall provides support and structure for the organisms – Allows for turgor pressure in plants

Animal No cell wall No chloroplast Small vacuoles Has centrioles Plant Cell wall Chloroplasts Large vacuole No centrioles