Ch 3 - the cell

who is Aristotle & what did he do?

• articulates theory of spontaneous generation

  • notion that life can arise from nonliving matter

• proporsed that life arose from nonliving material if material contained pneuma (spirit)

who is Francesco Redi & what did he do?

• performed an experiment that was 1 of the 1st to refute idea that maggots spontaneously generate on meat left out in open air

• predicted that preventing flies touching meat prevents maggots

who is John Needham & what did he do?

• published report of experiments where he briefly boiled broth infused w plant or animal matter in hopes to kill all preexisting microbes

  • observed that the broth had become cloudy & single drop contained many microscopic creatures

  • argued that new microbes must have arisen spontaneously

who is Lazzaro Spallanzani & what did he do?

• conducted Needham’s broth experiment

  • found that heated broth remained clear unless flasks were opened to air

• argued that life originates from a “life force“ that was destroyed during his extended boiling

who are the spontaneous generation?

• Aristotle

• Francesco Redi

• John Needham

• Lazzaro Spallanzani

who are the disproving spontaneous generation?

• Louis Pasteur

• Swan Neck Flask Experiment

who is Louis Pasteur & what is the swan neck flask experiment?

• filtered air through gun-cotton filter & found it full of microorganisms

• found that exposure to air wasn’t introducing a “life force“ to broth but rather airborne micoorganisms

• kept broths sterilized in swan neck flasks

• found that it stayed sterile unless flask was broken

what is a cell?

smallest unit of living organisms

what is the cell theory?

• all living things are made of cells

• all cells come from pre-existing cells

who is Robert hooke?

• 1st used term “cell“ to describe small chambers within cork that he observed under his own microscope

  • thin sections resembled honey comb pattern

    • each section was distinct from others

    • wasn’t aware that the cork cells were already dead

who is Robert Remak?

published convincing evidence that cells are derived from other cells as a result of cell division

who is Rudolfe Virchow?

• published editorial that popularized concept of cell theory - “omnis cellula a cellula“

  • is 2nd tenet of modern cell theory

what is germ theory?

states that diseases may result from microbial infection

what do greeks have to do w the germ theory?

• proposed miasma theory which held that diseases originated from particles emanating from decomposing matter

• ex: sewage or cesspits

who is Girolamo Fracastoro?

proposed that seed-like spores may transfer between individuals through direct contact, exposure to contaminated clothing, or through the air

who is Ignaz Semmelweis?

observed that people who gave birth in hospital wards staffed by physicians & medical students were more likely to suffer & die from puerperal fever after childbirth than those w midwives

what are Ignaz Semmelweis’ findings on puerperal fever? (1/2)

• saw medical students performing autopsies & then go on to carry out vaginal examinations w/o washing their hands

• didn’t know true cause of puerperal fever

what are Ignaz Semmelweis’ findings on puerperal fever? (2/2)

• proposed that physicians were transferring the causative agent to patients

• suggested cases would drop if medical staff washed their hands w chlorinated lime water b4 & after examining every patient

who is John Snow? (1/2)

• conducted studies to track source of cholera outbreaks in London

• traced to two specific water sources that were contaminated by sewage

who is John Snow? (2/2)

• showed cholera bacteria transferred via drinking water

• represents 1st known epidemiological study

• resulted in 1st known public health response to epidemic

who is Louis Pasteur?

• discovered properties of fermentation by microorganisms

• showed airborne microbes were cause of food spoilage

• proposed that they could also be responsible for causing infection

• foundation for germ theory of disease

who is Joseph Lister?

• trying to determine causes of postsurgical infections

• insisted on handwashing & practicing extreme cleanliness during surgery

• began to spray carbolic acid (disinfectant/antiseptic) during surgery

who is Robert Koch? (1/2)

• proposed series of postulates based on idea that the cause of a specific disease could be attributed to a specific microbe

  • able to ID causative pathogens of specific diseases such as anthrax, tuberculosis, & cholera

who is Robert Koch? (2/2)

• “one microbe, one disease“ concept

  • shifts away from miasma theory & into germ theory

what is the endosymbiotic theory?

• states that key organelles inside complex eukaryotic cells (esp mitochondria & chloroplasts) started as independent prokaryotic bacteria

• have symbiotic relationship w eukaryotic host

who is Konstantin Mereschkowski?

• suggested that chloroplasts may originate from ancestral photosynthetic bacteria living symbiotically inside eukaryotic cell

• proposed similar origin for nucleus of plant cells

• 1st articulation of endosymbiotic hypothesis & would explain how eukaryotic cells evolved from ancestral bacteria

who is Ivan Wallin?

• began to experimentally examine similarities between mitochondria, chloroplasts, bacteria to put endosymbiotic theory to test

• published series of papers supporting the theory

• claims to culture mitochondria as resulting from bacterial contamination

who is Lynn Margulis?

• published ideas that endosymbiotic hypothesis of origins of mitochondria & chloroplasts

• argued that eukaryotic organelles like mitochondria & chloroplasts are of prokaryotic origin

• presented growing body of microscopic, genetic, molecular biology, fossil, & geological data to support her claims

what are prokaryotes?

• small, simple, no nucleus, binary fission

• includes domain, bacteria, & archaea

what do all prokaryote cells have?

• plasma membrane

• ribosomes

• nucleic acid (nuceloid)

• cytoplasm

what are some other possible structures that prokaryotes have?

• capsule, cell wall, inclusion

• plasmid, flagellum, pilus

• fimbriae, endospores

what is the structure of phospholipids?

• hydrophilic head

  • water loving

• hydrophobic tails

  • water fearing

how is the plasma membrane structure of most bacterial & eukaryotic cell types?

bilayer composed mainly of phospholipids formed w ester linkages & proteins

what are the structures of plasma membrane?

• Bilayer

• Sterols

• Proteins

• Fluid Mosaic Model

• Regulation/Transport

what is the fluid mosaic model?

refers to ability of membrane components to move fluidly within plane of membrane

how do cells transport through the plasma membrane?

• passive transport

  • molecules moving from higher concentration to lower concentration w concentration gradient are transported by simple diffusion

• active transport

  • cells move molecules across their membrane against concentration gradients

  • requires ATP to move

what is passive transport?

• “w the gradient“

• simple

• facilitated

what is active transport?

• “against the gradient“

• membrane pumps

• group translocation

• endo & exo cytosis

what is gram positive cell wall?

• two layers

• thick peptidoglycan

what is gram negative cell wall?

• three layers

• outer membrane

• lipopolysaccharide

• porins

how do prokaryotic cells maintain morphology?

• by cell wall in combo w cytoskeletal elements

• cell walls help maintain turgor pressure & prevent plasmolysis

what happens during plasmolysis?

• cells w cell wall undergo plasmolysis

  • plasma membrane contracts & detaches from cell wall

  • there’s decrease in interior volume but cell wall remains intact

  • allows cell to maintain some shape & integrity for a period of time

what are eukaryotes? (1/2)

• larger, more complicated

• more recently evolved

• defining feature = Nuclei

what are eukaryotes? (2/2)

• membrane bound organelles

• both single celled & multi-celled organisms

• mitosis & meiosis (sexual)

• multiple, linear chromosomes

what is the appendage - flagella?

• run

  • long & linear movement

  • moving toward or away from chemical

• tumble

  • not responding to chemoatrractant or repellant

what is the appendage - fimbriae?

• commonly refers to short bristle-like proteins projecting from cell surface by hundreds

• enable cell to attach to surfaces & other cells

what is the appendage - pili?

commonly refers to longer, less numerous protein appendages that aid in attachment to surfaces

what is isotonic solution?

• has same solute concentration as another solution

• no net movement of water particles & overall concentration on both sides of cell membrane remains constant

what is hypertonic solution?

• has higher solute concentration than another solution

• water particles will move out of cell, causing crenation

what is hypotonic solution?

• has lower solute concentration than another solution

• water particles will move into cell, causing cell to expand & eventually lyse