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introduction
introduction
The transport of gases, nutrients, and wastes into and out of the cell is essential for the cell's survival. The cell membrane is the organelle responsible for transport. The substances that enter and leave the cell may be ions or molecules or, in some cases, micro-organisms or other cells.
The particle model of matter
The particle model of matter
The substances that enter and leave the cell can be regarded as particles, and their behaviour can be examined with reference to the particle model of matter.
Read Page 274
All matter is made up of particles
The particles of matter are constantly moving or vibrating
Particles of matter are attracted to one another or are bonded together
Particles have spaces between them that are smallest in solids and greatest in gases.
types of transport
types of transport
Pages 275-278
There are two different categories of cell transport:
Passive Transport: Movement of particles by the process of diffusion which requires no added energy for the movement to occur.
a. diffusion
b. facilitated diffusion
Active Transport: Transport of particles by way of protein carriers in the cell membrane which requires energy input because, in some cases, it is necessary for the cell to move particles against the concentration gradient.
Passive transport: DIFFUSSION
Passive transport: DIFFUSSION
Pages 275-278
Many people, young and old, enjoy a nice cup of tea now and then; but how many view making a cup of tea from a scientific point of view? Have you ever watched what happens when you place a tea bag into a cup of hot water? Even without stirring, color immediately begins to seep from the tea bag to the water and spread throughout the cup. This movement of color is evidence of diffusion - particles of tea moving from an area of higher tea concentration to an area of lower tea concentration.
Diffusion also plays an important role in the movement of various substances into and out of the cell through the cell membrane. You can better understand diffusion and other methods of transport through the cell membrane if you relate them to the particle model of matter.
Diffusion is when particles spread out.
Particles will always move from an area of high concentration to an area of low concentration.
A concentration gradient is a difference in concentration between two areas
Particles naturally move down the concentration gradient which means that they always move from high concentration to a low concentration
learning activities
learning activities
Turn to page 275 of the textbook and read “Diffusion.” You will study more about diffusion and how it occurs through the cell membrane.
What happens to the coffee aroma molecules released into a room after a period of time?
i. What is rate of diffusion?
ii. How can rate of diffusion be changed?
Define concentration gradient.
Why is the movement of a substance through diffusion called passive transport?
Why is the cell membrane considered to be a selectively permeable membrane?
State three conditions that determine whether materials will pass through a cell membrane.
Why does carbon dioxide leave a cell and oxygen enter a cell?
special type of diffusion- Osmosis
special type of diffusion- Osmosis
Read Pages 277-278
Diffusion of water through a semipermeable membrane.
The membrane blocks the diffusion of solute particles. Water flows instead.
Solute Sucks!- The side with more solute "sucks" the water from the other side.
Water always flows to where there is more solute in an attempt to even out the solute concentrations.
predicting movement of water by osmosis
predicting movement of water by osmosis
To predict the direction in which a net movement of water will occur, we need to compare the solute concentration.
Isotonic - the solute concentration between two areas is equal
Hypertonic - an area that has a higher solute concentration than another.
Hypotonic - an area that has a lower solute concentration than another.
learning activities
learning activities
Read the information in “Osmosis” on pages 277 and 278 of the textbook.
Carefully examine Figure C2.16.
Explain, in terms of water concentrations, why water flows from left to right in Figure C2.16.
2. Define the following terms with reference to concentration of solutions outside and inside a cell.
• hypertonic
• isotonic
• hypotonic
3. Answer questions 1 to 4 of “Skill Practice: Linking Conclusions to Hypotheses,” on page 279 of the textbook.
passive transport: Facilitated diffusion
passive transport: Facilitated diffusion
The lipid bilayer in the cell membrane allows only molecules of substances that are soluble in lipids to pass through. Substances that are not soluble in lipids need some other mechanism to pass through the membrane.
The protein part of the membrane is involved.
Channel proteins create pores or channels through which small water-soluble particles are able to move. The movement happens in response to the concentration gradient.
Carrier proteins: have ability to attach to larger molecules. Carrier proteins change shape and physically move the molecules across the membrane into teh cell.
Overview of passive transport
Overview of passive transport
active transport
active transport
Sometimes transport by protein carriers in the cell membrane require energy input to move particles against the concentration gradient, from an area of low concentration to an area of high concentration- this method is called active transport.
The energy needed for this movement is produced by the mitochondria through a process called cellular respiration and comes from a substance called Adenosine Triphosphate (ATP).
what if molecules that need to be taken in by the cell, or secreted by itm are too large to cross the cell membrane even with help of protein carriers?
what if molecules that need to be taken in by the cell, or secreted by itm are too large to cross the cell membrane even with help of protein carriers?
ENDOCYTOSIS
ENDOCYTOSIS
A vesicle forms around the particle and the cell membrane pinches off around it so that the vesicle is inside the cell.
exocytosis
exocytosis
When the cel wants to get rid of large waste particles, or needs to release a product molecule- A vesicle surrounds the particle, then moves to the plasma membrane and fuses with it. The vesicle then ruptures, releasing its contents into the surroundings.
learning activities
learning activities
Read pages 278 and 279 of the textbook and read the information in, “Facilitated Diffusion” and “Active Transport.” You will study different ways substances can pass through the cell membrane.
Define the terms channel proteins, carrier proteins, and facilitated diffusion.
What is active transport?
Where does the energy for active transport come from?
5d) How is active transport different from diffusion and facilitated diffusion?
Complete Check and Reflect on Page 283
Once you have completed the required readings and learning activities for sections C2.1-C2.2, you are now ready to complete the following lab:
Lab:
"C2 Cell Structure and Cell Function"
Next: You are now ready to move on to complete section C2.3
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