Class: Name: Date: 3 Movement of substances across cell ...bio662.dyndns.info/DSE/WS/ws_ch03_e.pdf · Different substances move across the cell ... of the carrier proteins can be

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New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)

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3 Movement of substances

across cell membrane

3.1 Cell membrane (Book 1A, p. 3-3)

A Structure of the cell membrane (Book 1A, p. 3-3)

� Singer and Nicolson proposed the (1) ______________ _______________ _______________

(流動鑲嵌模型) in 1972, which suggests that:

- the cell membrane is mainly made up of (2) _______________ (磷脂) and

(3) _______________

- phospholipid molecules are arranged in a (4) _______________ and protein molecules

are (5) _______________ (散佈) among them.

Meaning

Fluid Phospholipid molecules can move (6) ______________ (橫向地).

Mosaic Protein molecules are interspersed among the (7) _______________ molecules in

a mosaic pattern.

protein molecules

protein molecules

carbohydrate molecule

glycoprotein (糖蛋白)

phospholipid bilayer

outside of cell

inside of cell (cytoplasm)

▲ The fluid mosaic model of the cell membrane


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1 Phospholipids

� Phospholipids are a type of lipid. Their structure is similar to that of triglycerides except one

of the fatty acid molecules is replaced by a (8) _____________ _____________ (磷酸鹽基團).

Triglyceride molecule Phospholipid molecule

one glycerol molecule

three fatty acid molecules

glycerol

two fatty acid molecules

phosphate group

� Features of a phospholipid molecule:

Phosphate group Fatty acid

� (9) ______________ (Polar / Non-polar)

� Forms the (10) _______________ ‘head’

� (11) _____________ (Attracted / Repelled)

by water molecules

� (12) ______________ (Polar / Non-polar)

� Forms the (13) _______________ ‘tails’

� (14) _____________ (Attracted / Repelled)

by water molecules

� Arrangement of phospholipid molecules in the cell membrane:

The (15) _____________

heads face the aqueous

environment inside and

outside of cell.

The (16) ___________

tails point inwards.

outside of cell

inside of cell

▲ Phospholipid molecules arranged in a bilayer


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2 Proteins

� Some proteins are attached to the surface of the phospholipid bilayer, some are

(17) _______________ half-way in the bilayer and others (18) _______________ the entire

bilayer.

� Carbohydrates are attached to some proteins to form (19) _______________, which may act

as antigens or receptors.

Membrane protein Function

I Channel protein a Involved in active transport to carry substances across the membrane

II Carrier protein b Receives chemical messengers (e.g. hormones) outside the cell

III Antigen c Provides channels across the membrane for transporting certain ions

IV Receptor and small, polar molecules

V Enzyme d Speeds up reactions in the cell

e For cell recognition (識別)

I: (20) _______________ II: (21) _______________ III: (22) _______________

IV: (23) _______________ V: (24) _______________

B How is the membrane structure related to its properties and

functions? (Book 1A, p. 3-6)

small, non-polar molecule

small, polar molecules and

certain ions

large molecule

channel protein

carrier protein

outside of cell

inside of cell

▲ Different substances move across the cell membrane along different paths


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Structure of cell membrane Property and function

� The cell membrane is mainly

made up of (25) ______________

and (26) _______________.

� The phospholipid molecules are

arranged in a (27) ____________.

� Some protein molecules act as

channels or carriers.

� This makes the cell membrane (28) ____________

permeable.

� Only small, (29) _____________ molecules can

move across the phospholipid bilayer.

� Small, (30) _____________ molecules and certain

ions can move across the membrane through

channel proteins or carrier proteins.

� The phospholipid molecules can

move laterally, i.e. the cell

membrane is (31)______________

in nature.

� This makes the cell membrane (32) ___________,

so that it can change its (33) _____________ and

fuse during phagocytosis and cell division.

� (34) _______________ molecules

are interspersed among the

phospholipid bilayer.

� This makes the cell membrane strong enough to

(35)_____________ the cell contents.

3.2 Movement of substances across membranes (Book 1A, p. 3-9)

A Diffusion (Book 1A, p. 3-9)

� Particles of liquids and gases can move about freely. They tend to distribute evenly.

� Diffusion (擴散) is the net movement of particles down a (1) ____________ _____________,

i.e. from a region of (2)_____________ (higher / lower) concentration to a region of

(3)_____________ (higher / lower) concentration, until the particles become evenly

distributed.

� When the particles are evenly distributed, there is no (4)_____________ movement of

particles between the two regions but the particles are still moving (5)_____________ in all

directions.

� Diffusion is a (6)_____________ process and does not require (7)_____________.


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� Factors affecting the rate of diffusion:

Factor Effect on the rate of diffusion

Concentration gradient The steeper the concentration gradient is, the (8) _____________ the

rate of diffusion.

Temperature At higher temperatures, particles have (9)_____________ kinetic

energy and collide (10)_____________ frequently, resulting in a

(11)_____________ rate of diffusion.

Size of particles Small particles diffuse (12) _____________ than large particles.

Distance The (13) _____________ the distance is between two regions of

different concentrations, the higher the rate of diffusion.

Surface area For the diffusion through a membrane, the (14) _____________ the

surface area of the membrane is, the higher the rate of diffusion.

Diffusion is important for:

� (15) _____________ of materials between the cell and the environment, e.g. obtaining

(16) _____________ and nutrients, and removing (17) _____________ like carbon dioxide

� allowing substances in cells to be (18) _____________ throughout the cytoplasm.

concentration gradient exists particles are evenly distributed

▲ Diffusion

higher concentration

lower concentration

particles move randomly in all directions

net movement of particles


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B Osmosis (Book 1A, p. 3-11)

� Osmosis (滲透) is the net movement of (19) _____________ molecules through a

(20)_____________ _____________ membrane from a less concentrated solution to a more

concentrated solution.

� It is a (21) _____________ process and does not require (22) _____________.

� (23) _____________ _____________ (水勢) describes the tendency of water molecules to

move from one place to another. Pure water has the (24) _____________ (highest / lowest)

water potential which is defined as (25) _____________.

� The presence of solute particles (26) _____________ (raises / lowers) the water potential of a

solution. All solutions have a water potential lower than that of pure water, i.e. a

(27)_____________ value.

� Osmosis can be redefined as the net movement of water molecules from a region of

(28)_____________ (higher / lower) water potential to a region of (29) _____________

(higher / lower) water potential.

water molecule

sucrose molecule

higher water potential (dilute sucrose solution)

lower water potential (concentrated sucrose

solution)

▲ Osmosis

differentially permeable membrane

net movement of water molecules


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� Go to

Practical 3.1 Demonstration of osmosis using dialysis tubing

(Book 1A, p. 3-12; Practical Workbook for SBA 1A, p. 3-1)

Practical 3.2 Demonstration of osmosis using living animal tissue


� Cells and osmosis:

Net movement of

water Animal cell Plant cell

In hypotonic

(低滲的) solution

(30) _____________

(Enters / Leaves) the

cell

(31)_______________ and

finally (32) ___________

(爆裂)

Becomes

(33) ____________ (膨脹)

In hypertonic

(高滲的) solution

(34) _____________

(Enters / Leaves) the

cell

(35) _______________

(萎縮) and becomes

wrinkled (皺褶)

Becomes flaccid (軟縮)

and (36) ______________

(質壁分離)

In isotonic

(等滲的) solution

No net movement Remains the same

Remains the same

� Osmosis is important for the movement of (37) _____________ in and out of cells, e.g. during

absorption of water in small intestines and plant roots.


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� Go to

Practical 3.3 Study of osmosis in red blood cells


Practical 3.4 Study of osmosis in living plant cells


Practical 3.5 Study of osmosis in living plant tissue


C Active transport (Book 1A, p. 3-21)

� Active transport (主動轉運) is the transport of substances across the cell membrane

(38) ______________ a concentration gradient.

� It involves (39) ______________ proteins. Only substances that fit the (40) _____________

of the carrier proteins can be transported by active transport.

� It is an (41) ______________ process and requires energy. Therefore it only occurs in

(42) ______________ cells which can release energy by (43) ______________.

Active transport is important for obtaining useful substances, e.g.

� the absorption of (44) _____________ in human small intestines

� the absorption of (45) _____________ from the soil into the roots of plants.

lower concentration

higher concentration

carrier protein

The substance to be transported binds to a carrier protein.

The carrier protein changes its shape using energy.

The substance is released on the other side of the cell membrane.

▲ Active transport


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D Phagocytosis (Book 1A, p. 3-22)

� Phagocytosis (吞噬) is the uptake of large particles into the cell by the formation of a

(46) _______________ or (47) _______________ (偽足) at the cell membrane.

� It is an (48) _____________ process and requires energy.

Phagocytosis is important for:

� (49) _______________ of some unicellular organisms, e.g. Amoeba engulfs food particles

� body defence against diseases, e.g. in humans and other mammals, certain

(50) _____________ _____________ cells engulf harmful microorganisms.

1 At the cell membrane, a pit or pseudopodium is formed to engulf the target particle

2 The particle is enclosed in a small vacuole.

3 The cell releases enzymes to digest the particle in the vacuole.

4 The digested products diffuse to the cytoplasm.

outside of cell

inside of cell

cell membrane

enzyme

▲ A particle is taken into a cell by phagocytosis and is then digested

digested products


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Answers

Ch 3 Movement of substances across cell membrane

3.1 1 fluid mosaic model 2 phospholipids 3 proteins 4 bilayer 5 interspersed

6 laterally 7 phospholipid 8 phosphate group 9 Polar 10 hydrophilic

11 Attracted 12 Non-polar 13 hydrophobic 14 Repelled 15 hydrophilic

16 hydrophobic 17 embedded 18 span 19 glycoproteins 20 c

21 a 22 e 23 b 24 d 25 phospholipids

26 proteins 27 bilayer 28 differentially 29 non-polar 30 polar

31 fluid 32 flexible 33 shape 34 Protein 35 support

3.2 1 concentration gradient 2 higher 3 lower 4 net

5 randomly 6 all 7 energy 8 higher 9 more

10 more 11 higher 12 faster 13 shorter 14 larger

15 exchange 16 oxygen 17 waste 18 distributed 19 water

20 differentially permeable 21 passive 22 energy 23 Water potential

24 highest 25 zero 26 lowers 27 negative 28 higher

29 lower 30 Enters 31 Swells 32 bursts 33 turgid

34 Leaves 35 Shrinks 36 plasmolysed 37 water 38 against

39 carrier 40 shape 41 active 42 living 43 respiration

44 glucose 45 minerals 46 pit 47 pseudopodium 48 active

49 nutrition 50 white blood

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Class: Name: Date: 3 Movement of substances across cell ...bio662.dyndns.info/DSE/WS/ws_ch03_e.pdf · Different substances move across the cell ... of the carrier proteins can be