Cells EXAM 2

• reproduce via DNA
• grow and develop
• take energy from environment
• sense and respond to environment (plant towards sun) 
• maintain constant internal conditions (homeostasis)
• evolve over time

smallest units of life

• cell needs a surface area large enough
• to allow for adequate nutrients to enter and to rid its wastes

• Small cells are likey
• to have any adequate surface area

• Originated from the work of Schleiden
• and Schwann in 1838-9 

  Virchow

• 1.All living organisms are composed of one
• or more cells

2.Cells are the smallest units of life

• 3.New cells come only from pre-existing
• cells by cell division

• Magnification
• Resolution
• Contrast

Ratio between the size of an image produced by a microscope and its actual size

• ¨Ability to observe two adjacent objects
• as distinct from one another

• ¨How different one structure looks from
• another – enhanced by dyes

• one uses light another uses electron beam
• electron has more resolution

• transmission - some
• electrons are scattered while others pass through to form an image

• scanning -  Beam
• scans surface to make 3D image

both no live speciment

• Simple cell structure
• Lack a membrane-enclosed nucleus

2 categories- bacteria and archaea

• Plasma membrane
• Cytoplasm
• membrane
• Nucleoid
• Ribosomes

• Cellwall
• Glycocalyx-traps water, protection
• Capsule - may help evade immune system
• Appendages- pilli flagella (locomotion)

• nucleus
• exhibit compartmentalization via organelles
• Shape, size, and organization of cells vary considerably among different species and
• even among different cell types of the same species

• isolate reactions - each part has it's own job
• more surface area

endomembrane system -- organelles that communicate with one another via membrane channels and small vesicles

• Energy related organelles - Mitochondria & chloroplasts (energy independent &
• self-sufficient)