7.4 Homeostasis and Cells
Cells have the same basic composi6on, and the same kinds of organelles, but not all living
things are the same
Unicellular Organisms ! Homeostasis – rela6vely constant internal physical
and chemical condi6ons
! Single-‐celled organisms (protozoans, yeast, algae, bacteria) are living too
! Maintain homeostasis
! Grow
! Respond to the environment
! Transform energy
! Reproduce
Mul6-‐cellular Organisms ! Cells have a certain job in the body and
are specialized for their task
Human trachea epithelial cells -‐ have cilia to catch debris when you breathe in air !
Pollen grains from pine tree -‐ Tiny, lightweight, protec6ve covering . Float in the wind un6l they land on seed cone
Levels of Organiza6on ! Cells make…
! Tissues, which make…
! Organs, which make…
! Organ systems, which makes…
! Organisms
Cellular Communica6on ! Cells are specialized, but
interdependent
! Cells MUST communicate effec6vely and this is done by means of “chemical signals”.
! Some cells form a connec6on to another cell, called cellular junc.ons
! Signals pass through junc6ons, but only if they have the right receptor – specific protein that has specific shape that molds to a specific molecular messenger
Ex: juncAons in the heart – electrical signals pass through junc6ons to make heart contract and pump blood