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Class: ( Name: ) Date: 3 Movement of substances across cell membrane 3.1 A Cell membrane (Book 1A, p. 3-3) 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. protein molecules carbohydrate molecule outside of cell glycoprotein (糖蛋白) phospholipid bilayer inside of cell (cytoplasm) protein molecules ▲ The fluid mosaic model of the cell membrane Meaning Fluid Phospholipid molecules can move (6) ______________ (橫向地). Mosaic Protein molecules are interspersed among the (7) _______________ molecules in a mosaic pattern. New Senior Secondary Mastering Biology (Second Edition) - 18 - Oxford University Press 2014 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 phosphate group one glycerol molecule three fatty acid molecules glycerol two fatty acid molecules Features of a phospholipid molecule: Phosphate group Fatty acid (9) ______________ (Polar / Non-polar) (12) ______________ (Polar / Non-polar) Forms the (10) _______________ ‘head’ Forms the (13) _______________ ‘tails’ (11) _____________ (Attracted / Repelled) (14) _____________ (Attracted / Repelled) by water molecules by water molecules Arrangement of phospholipid molecules in the cell membrane: outside of cell The (15) _____________ heads face the aqueous environment inside and outside of cell. The (16) ___________ tails point inwards. inside of cell ▲ Phospholipid molecules arranged in a bilayer New Senior Secondary Mastering Biology (Second Edition) - 19 - Oxford University Press 2014 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 and small, polar molecules IV Receptor 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 outside of cell inside of cell channel protein carrier protein ▲ Different substances move across the cell membrane along different paths New Senior Secondary Mastering Biology (Second Edition) - 20 - Oxford University Press 2014 Structure of cell membrane Property and function The cell membrane is mainly This makes the cell membrane (28) ____________ made up of (25) ______________ permeable. and (26) _______________. Only small, (29) _____________ molecules can The phospholipid molecules are move across the phospholipid bilayer. arranged in a (27) ____________. Small, (30) _____________ molecules and certain Some protein molecules act as ions can move across the membrane through channels or carriers. channel proteins or carrier proteins. The phospholipid molecules can This makes the cell membrane (32) ___________, move laterally, i.e. the cell so that it can change its (33) _____________ and membrane is (31)______________ fuse during phagocytosis and cell division. in nature. (34) _______________ molecules This makes the cell membrane strong enough to are interspersed among the (35)_____________ the cell contents. phospholipid bilayer. 3.2 Movement of substances across membranes A Diffusion (Book 1A, p. 3-9) (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)_____________. New Senior Secondary Mastering Biology (Second Edition) - 21 - Oxford University Press 2014 concentration gradient exists particles are evenly distributed higher lower concentration concentration net movement of particles particles move randomly in all directions ▲ Diffusion Factors affecting the rate of diffusion: Factor Concentration gradient Effect on the rate of diffusion 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. New Senior Secondary Mastering Biology (Second Edition) - 22 - Oxford University Press 2014 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. differentially permeable membrane water molecule sucrose molecule higher water potential (dilute sucrose solution) lower water potential (concentrated sucrose solution) net movement of water molecules ▲ Osmosis New Senior Secondary Mastering Biology (Second Edition) - 23 - Oxford University Press 2014 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 (Book 1A, p. 3-13; Practical Workbook for SBA 1A, p. 3-5) Cells and osmosis: Net movement of water In hypotonic (低滲的) solution (高滲的) solution In isotonic (等滲的) Plant cell (30) _____________ (31)_______________ and Becomes (Enters / Leaves) the finally (32) ___________ (33) ____________ (膨脹) cell In hypertonic Animal cell (爆裂) (34) _____________ (35) _______________ Becomes flaccid (軟縮) (Enters / Leaves) the (萎縮) and becomes and (36) ______________ cell wrinkled (皺褶) (質壁分離) No net movement Remains the same Remains the same solution 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. New Senior Secondary Mastering Biology (Second Edition) - 24 - Oxford University Press 2014 Go to Practical 3.3 Study of osmosis in red blood cells (Book 1A, p. 3-16; Practical Workbook for SBA 1A, p. 3-8) Practical 3.4 Study of osmosis in living plant cells (Book 1A, p. 3-17; Practical Workbook for SBA 1A, p. 3-10) Practical 3.5 Study of osmosis in living plant tissue (Book 1A, p. 3-18; Practical Workbook for SBA 1A, p. 3-13) 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) ______________. lower concentration carrier protein higher concentration 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 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. New Senior Secondary Mastering Biology (Second Edition) - 25 - Oxford University Press 2014 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. cell membrane 1 At the cell membrane, a pit or pseudopodium is formed to engulf the target particle outside of cell inside of cell digested products 2 The particle is enclosed in a small vacuole. 4 The digested products diffuse to the cytoplasm. 3 The cell releases enzymes to digest the particle in the vacuole. enzyme ▲ A particle is taken into a cell by phagocytosis and is then digested 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. New Senior Secondary Mastering Biology (Second Edition) - 26 - Oxford University Press 2014 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 2 higher 3 lower 4 net 3.2 1 concentration gradient 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 New Senior Secondary Mastering Biology (Second Edition) - 27 - Oxford University Press 2014