biology chapter 7.31 homeostasis and cell transport biology class pg 96-111 a macrophage consuming a...

Biology Chapter 7.3 1

Homeostasis and cell transport

Biology classPg 96-111

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

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 AQ:What is phagocytosis?

A: phago+ to eat, cyto = cellQ: 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 KineticA: ability to do work, stored E, in motion E

Q: 2 main components of cell membranesA: 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 equilibriumDiffusion of molecules depends on:1. Size and type of molecule2. Chemical nature 3. Polar or nonpolar- (carbon dioxide and

oxygen are nonpolar dissolve in lipids)http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP1903

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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:1. HypOtonic- water is higher on outside- swell2. Hypertonic-water is higher inside cell- shrink3. Isotonic-at equilibriumhttp://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP11003http://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,

swelling2. Plasmolysis- loss of water, cell shrink, plant wilt3. Cytolysis- bursting of a cellwww.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 ways1. endocytosis2 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 cell’s

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?v=XV8jawQwRag&feature=related

2. Phagocytosis- large particles, whole cells (eating cell)

http://www.youtube.com/watch?v=7VQU28itVVw&feature=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?v=1w10R9lv7eQ&feature=related

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Do you know?1. 4 types of passive transport

2. Types of active transport

3. Active vs. Passive

websites• Interactive transport

– http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm

• Lab bench– http://www.phschool.com/science/

biology_place/labbench/lab1/intro.html• Conditions

- http://www.glencoe.com/sites/common_assets/science/virtual_labs/LS03/LS03.html

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