National 5 Biology | Unit 1 | Key Area 2: Transport Across Cell Membranes

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1
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Why treat the cell membrane in high temperatures?
The extreme heat ==denatures the proteins== present in the cell membrane.
2
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Give examples of internal cell structures surrounded by a cell membrane:
Nucleus, mitochondria, sap vacuole, chloroplast
3
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What is the function of the cell membrane?
-Controls what enters and exits the cell (selectively permeable)
-Allows different sets of conditions to be maintained in different 'compartments'.
4
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Why treat the cell membrane with acid?
The acid pH conditions ==denature the proteins and the overall shape==.
5
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Why treat the cell membrane with alcohol?
The alcohol ==dissolves the (phospho)lipids== present in the cell membrane.
6
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The cell membrane consists of _____ and _____ molecules.
Protein; phospholipid
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What is a phospholipid?
A molecule made from phosphorus (phospho-) and fat (-lipid)
8
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Diffusion
The process by which ==molecules move from an area of higher concentration to an area of lower concentration== until the concentration becomes equal.
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Concentration gradient
The ==difference in concentration== that exists between an area of higher concentration and an area of lower concentration.
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During diffusion, the movement of molecules always occurs _____ a concentration gradient from _____ to _____ concentration.
Down; higher; lower
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All solids, liquids and gases are made of _____. In liquids and gases, these can move around _____. In solids, they are _____ free to move.
Molecules; freely; less
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Diffusion requires a _____ _____ of the substance.
Concentration gradient
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Diffusible substances are _____, _____ and _____ solids.
Gases; liquids; dissolved
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During diffusion, there must not be any form of _____ between the regions of differing concentration.
Barrier
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Diffusion is a _____ process and will occur in _____ or _____ systems.
Passive; living; dead
16
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Factors to increase the rate of diffusion include:
-Increasing the temperature
-Increasing the concentration gradient
-Increasing the surface area
17
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Diffusion is used by cells for the entry of useful substances such as _____ and _____, as well as for the removal of _____ substances such as carbon dioxide.
Oxygen; glucose; waste
18
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Movement of materials between cells in multicellular organisms is normally carried out by _____ _____ _____, eg. the bloodstream.
Special transport systems
19
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As cells become _____, diffusion cannot occur fast enough to transport all the materials required. This is because the _____ _____ becomes relatively small compared to the overall _____.
Larger; surface area; volume
20
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Larger objects have _____ surface area:volume ratios than smaller objects. Therefore a cell cannot become too large, otherwise its _____ _____ would be too small for adequate _____ of molecules in and out.
Smaller; surface area; transport
21
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The cell membrane contains tiny _____ through which molecules can diffuse. The molecules have to be _____ than these in order for them to pass through the cell membrane.
Pores; smaller
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The cell membrane is _____ to _____ molecules such as protein and _____ substances such as starch.
Impermeable; large; insoluble
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The cell membrane is _____ permeable to _____ molecules such as oxygen, glucose, water and carbon dioxide.
Fully; small
24
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The cell wall (of plant cells) have very large _____, which means it is _____ permeable to dissolved substances, regardless of size.
Pores; fully
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Osmosis
The movement of ==water molecules== from an ==area of higher water concentration to an area of lower water concentration== ==through a selectively permeable membrane==.
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During osmosis, the movement of molecules always occurs _____ a concentration gradient from _____ to _____ concentration.
Down; higher; lower
27
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For water to enter a cell via osmosis, it must be _____.
Alive
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If water enters a cell via osmosis, it means the water concentration outside of the cell is _____ than the water concentration inside the cell. The water molecules move along the _____ _____.
Greater; concentration gradient
29
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If water exits a cell via osmosis, it means that the water concentration outside the cell is _____ than the water concentration inside the cell. The water molecules move to _____ the concentration in both areas.
Lower; equalise/neutralise
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If there is no overall movement of water in the cell and its surroundings, then the concentration gradient is _____ in both areas.
Even
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Even if the concentration gradient is even, molecules will still _____ to move.
Continue
32
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If an animal cell is placed in a concentrated salt solution, what would happen?
==Water would leave the cell==, since there is a lower water concentration outside of the cell than inside. Since there is no cell wall to retain the shape, ==the whole cell would shrink==.
33
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If a plant cell was placed in a concentrated salt solution, what would happen?
==Water would diffuse out the cell by osmosis==, since there is a lower water concentration outside of the cell than inside. Most of the water lost comes from the vacuole and cytoplasm, so the ==contents of the cell shrinks==, but the ==cell wall retains its shape==.
34
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Plasmolysis
This happens when ==a cell shrinks inside its cell wall due to extreme water loss==, while the cell wall itself remains intact. This is a ==reversible change== (pure water).
35
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If an animal cell was placed in pure water, what would happen?
==Water would pass into the cell==, since there is a higher water concentration outside the cell than inside. Since there is no cell wall, ==the cell would eventually burst==.
36
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If a plant cell was placed in pure water, what would happen?
==Water would diffuse into the cell by osmosis==, since there is a higher water concentration outside the cell wall than inside. The ==cell wall prevents the cell from taking in too much water== and bursting.
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When no more water can enter a cell via osmosis, the cell is said to be _____
Turgid
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Turgor is very important to plants, as turgid cells provide _____ for the stem. If a non-woody plant loses too much water it will _____.
Support; wilt
39
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Water will constantly enter an amoeba via _____. The unicellular animal uses a _____ ____ to constantly remove water. It is an energy-required process, since water is moved _____ its concentration gradient.

Osmosis; contractile vacuole; against

40
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Active transport requires _____ from the cell's _____.
Energy; metabolism
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Active transport uses _____ in the cell membrane to transport substances across the membrane.
Proteins
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Active transport moves molecules _____ the concentration gradient. Molecules are moved from an area of _____ concentration to an area of _____ concentration.
Against; lower; higher
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During active transport, an _____ concentration of molecules or ions can be maintained on one side of the membrane.
Uneven
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What are the benefits of active transport?
-Useful molecules can be kept inside a cell (eg. glucose)
-Unwanted molecules can be kept outside of a cell (eg. carbon dioxide)