Chapter 2: cells

Cells as the basic structural feature of life on Earth, including the distinction between prokaryotic and eukaryotic cells // Surface area to volume ratio as an important factor in the limitations of cell size and the need for internal compartments (organelles) with specific cellular functions

cell theory

1. all living things are made of cells

2. cells are the smallest and most basic unit of life

3. all cells come from pre-existing cells

MRS GREEN

• Movement

• Respiration

• Sensitivity to Stimuli

• Growth

• Reproduction

• Equilibrium (homeostasis)

• Excretion

• Nutrition

are viruses considered an organism?

no

• no movement

• no respiration / metabolism

• no growth

• cannot reproduce independently

prokaryotes

• no membrane-bound organelles

• minimal defined internal structure

• no defined structure to hold DNA (e.g. nucleus)

• forms unicellular organisms

  • e.g. bacteria, archaea

eukaryotes

• more complex

• membrane-bound structures (organelles)

• unicellular / multicellular

  • multicellular = animalia, plantae, fungi, protista

  • unicellular = paramecium

• organelles held by cytoskeleton

differences between prokaryotes and eukaryotes

similarities between prokaryotes and eukaryotes

• both have cell membrane / plasma membrane

• cytoplasm

• both use DNA as genetic blueprint

• ribosomes

animal vs plant cells

surface area

the area of the plasma membrane

• nutrient exchange, waste removal, communication

• increased SA = increased efficiency of molecule exchange with external environment

volume

cytoplasm

• increased volume = increased metabolic needs

as the cell gets larger…

SA:V decreases

how do larger cells overcome size?

• grow more nuclei for proteins

• cell protrusions —> folds —> increased SA

• divide into smaller cells

effective shapes of cells

• highest in flattened

• lowest in spheres

purpose of SA:V

exchange of materials (e.g. glucose, oxygen) between cell and environment can be exchanged quickly

electron microscopes

• powerful

• uses beams of electrons, not light

• transmission = inside

• scanning = surface

• x million magnification

types of microscopes

steps for using a light microscope

1. select lowest power objective lens

2. specimen must be in the center

3. adjust coarse focus knob

4. adjust fine focus knob

5. zoom in (highest power objective lens)

6. re-adjust fine focus lens