Homeostasis and cell transport

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Homeostasis and cell transport

• Biology class
• Pg 96-111

A macrophage consuming a fungal spore shows off
modo's subsurface
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Key Terms

• Diffusion
• Facilitated diffusion
• Osmosis
• Isotonic
• Hypertonic
• Osmotic pressure
• Active transport
• Passive transport
• Homeostasis
• Endocytosis
• Exocytosis
• Hypotonic
• Equilibrium
• Contractile vacuole

• Plasmolysis
• Cytolysis
• Pinocytosis
• Phagocytosis
• Concentration gradient

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What to know

• Explain how an equilibrium is established as a
  result of diffusion.
• Distinguish between diffusion and osmosis.
• Explain how substances cross the cell membrane
  through facilitated diffusion.
• Explain how ion channels assist the diffusion of
  ions across the cell membrane.
• Distinguish between passive and active transport.
• Compare endocytosis and exocytosis

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Q and A

• QWhat is phagocytosis?
• A phago to eat, cyto cell
• Q How this kind of phagocytosis is useful to
  animal. (96)
• A the immune system cells may stop tumors from
  growing
• Q What is Energy? Potential and Kinetic
• A ability to do work, stored E, in motion E
• Q 2 main components of cell membranes
• A lipids and proteins
• Q What does it mean to say a cell is selectively
  permeable?
• A Only some substances can cross the membrane

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Passive Transport

• Homeostasis the maintenance of a stable level of
  internal conditions even though environmental
  conditions are constantly changing. (temp, water
  content, pH)
• Cell membranes help organisms maintain
  homeostasis by controlling what substances may
  enter or leave cells. Some substances can cross
  the cell membrane without any input of energy by
  the cell in a process know as passive transport.

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Types of Passive Transport

1. Diffusion
2. Osmosis
3. Facilitated diffusion
4. Diffusion through ion channels

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1. Diffusion

• Is the movement of molecules from one area of
  higher concentration to an area of lower
  concentration.
• The difference in the concentration of molecules
  across a distance is called a concentration
  gradient.
• It is driven by kinetic energy of molecules
  (constant motion)
• Move from High to low or down the gradient
• Equilibrium when the concentration of the
  molecules are the same throughout the space

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Diffusion across a membrane

• Cell membranes allow some molecules to pass
  through- but not all
• Goes from high to low- simple diffusion till it
  reaches an equilibrium
• Diffusion of molecules depends on
• Size and type of molecule
• Chemical nature
• Polar or nonpolar- (carbon dioxide and oxygen are
  nonpolar dissolve in lipids)
• http//www.wisc-online.com/objects/ViewObject.aspx
  ?IDAP1903

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2. Osmosis

• Water molecules diffuse across a cell membrane
  from H to L
• Osmosis does not require cells to expend energy
  (passive)
• Directions
• HypOtonic- water is higher on outside- swell
• Hypertonic-water is higher inside cell- shrink
• Isotonic-at equilibrium
• http//www.tvdsb.on.ca/westmin/science/sbi3a1/Cell
  s/Osmosis.htm
• http//www.wisc-online.com/objects/ViewObject.asp
  x?IDAP11003
• http//www.goldiesroom.org/Shockwave_Pages/osmosis
  20demo.htm

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How cells deal with Osmosis

• If they are in a isotonic environment no
  difficulty keeping movement of water
• If in a hypotonic environment- water is
  constantly diffuses into these organisms- they
  use a contractile vacuoles to rid the excess
  water- this pumping action requires energy and is
  not passive
• 3 reactions to environments
• 1. Turgor pressure- pressure of water pushing
  cell walls, swelling
• 2. Plasmolysis- loss of water, cell shrink, plant
  wilt
• 3. Cytolysis- bursting of a cell
• www.linkpublishing.com/video-transport.htm

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3. Facilitated Diffusion

• Used in molecules that can not easily diffuse
  through cell membranes
• May be too large or not soluble in lipids
• Special proteins called carriers (specific) will
  assist the molecules across- molecules attached
  themselves to the carriers and are brought into
  the cells (glucose is too large)

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4. Diffusion through ion channels

• Transport ions from H to L
• They are not soluble in lipids and can not be
  passed in the membranes- must travel through the
  specific channels
• The channels can have gates to allow some ions to
  pass and keep others out

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Active Transport

• In many cases, cells must move materials from an
  area of lower concentration to an area of higher
  concentration, or up their concentration
  gradient. Such movement of materials is know as
  active transport. Unlike passive transport, AT
  requires a cell to expend ENERGY.

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Cell membrane pumps

• Move substance from Lower to Higher
  concentrations- requires energy (going up a hill
  requires work)
• Sodium-potassium pump-in animals and used a
  carrier protein organisms need a high Na
  outside the cell while having higher K inside
  the cells this pump maintains the differences
• http//www.goldiesroom.org/Shockwave_Pages/active
  20transport.htm

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Movement in Vesicles

• Some molecules are too large to pass through the
  cell membrane- How do you get the larger
  molecules into the cells?
• Two ways
• 1. endocytosis
• 2 exocytosis

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1. Endocytosis- In cell

• The process by which cells ingest external fluid,
  macromolecules, and large particles
• Materials are enclosed by a portion of the cells
  membrane than the pouch pinches off from the
  cells and becomes a membrane-bound organelle
  called a vesicle.
• Two types
• 1. Pinocytosis- solutes or fluids (drinking
  cell)
• http//www.youtube.com/watch?vXV8jawQwRagfeature
  related
• 2. Phagocytosis- large particles, whole cells
  (eating cell)
• http//www.youtube.com/watch?v7VQU28itVVwfeature
  related
• Phagocytes- are organisms that used phagocytosis

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• Phagocytosis - Pinocytosis

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2. Exocytosis- out cell

• The process by which a substance is released from
  the cell through a vesicle that transports the
  substance out of the cell
• Used to release large molecules such as proteins,
  waste products or toxins
• Demo http//www.youtube.com/watch?v1w10R9lv7eQf
  eaturerelated

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Do you know?

• 4 types of passive transport
• 2. Types of active transport
• 3. Active vs. Passive

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websites

• Interactive transport
• http//www.wiley.com/legacy/college/boyer/04700037
  90/animations/membrane_transport/membrane_transpor
  t.htm
• Lab bench
• http//www.phschool.com/science/biology_place/labb
  ench/lab1/intro.html
• Conditions
• http//www.glencoe.com/sites/common_assets/science
  /virtual_labs/LS03/LS03.html