Download Homeostasis and the cell membrane

Homeostasis
Standard
 SB1. Students will analyze the nature of the
relationships between structures and functions in
living cells.
 a. Explain the role of cell organelles for both
prokaryotic and eukaryotic cells, including the cell
membrane, in maintaining homeostasis and cell
reproduction.
 d. Explain the impact of water on life processes (i.e.,
osmosis, diffusion)
Essential Question
How does the cell membrane
help maintain homeostasis?
What is Homeostasis
 The ability of the body, or a cell, to maintain a constant internal
environment in response to external changes.
 Examples:
 Body temperature 98.6 degrees
 Shiver when cold
 Sweat when hot
 Apoptosis
 Cell self destructs in response to stress
 Keeps issues within that cell from spreading to other cells
 Hormone signals
 Release of insulin in response to high glucose levels
 This reduces high blood sugar
 Epinephrine-increases heart rate, muscle strength, and sugar
metabolism
 Cortisol-increases sugar in bloodstream
Cell membrane and homeostasis
 Cell membrane
 Phospholipid bilayer
 Selectively permeable
 controls what goes in an out of cell thru
channels, carriers and pumps
 Water flows freely by diffusion
 Controls hormone release, nutrient
flow, and water flow
 Two ways thru:
 Passive transport
 High concentration to low
concentration
 Active transport
 Low concentration to high
concentration
 Requires energy
Passive Transport
 Two types
 Diffusion
 Facilitated diffusion
 Facilitated Diffusion
 Examples:
 Glucose entering the
cell for respiration
 Amino acids entering
and leaving the cell for
protein synthesis
 Diffusion
 Examples:
 Gas exchange for
photosynthesis
 carbon dioxide from air to leaf,
oxygen from leaf to air.
 Gas exchange for respiration
 oxygen from blood to tissue
cells, carbon dioxide in
 Water sucked up by roots
 Osmosis
Diffusion Example
Active Transport
 Three types
 Endocytosis
 Exocytosis
 Ion pumps
 Endocytosis
 Examples
 Pinocytosis (‘cell drinking’)
 Uptake of large molecules
(DNA, protein) from solution
 Phagocytosis (‘cell eating’)
 Uptake of solid particles by a
cell
 Amoebas feeding
 Phagocytes engulfing
bacteria.
 Exocytosis
 Examples
 Protein packaging into
vesicles and delivery to
other cells
 Removal of waste
 Ion pumps
 Examples
 Re-absorption of glucose,
amino acids and salts by the
kidneys.
 Sodium/potassium pump in
cell membranes (especially
nerve cells)
Ion pump
Let’s Review the details
Grab a cell transport worksheet