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Chapter 2: Cells Activity 2.1 1 A B C D E F G Eyepiece or ocular lens Objective lens Stage Mirror Coarse focus Fine focus Body 2 a Eyepiece Part of the microscope on which the specimen is placed Sharpens the focus on high power b Coarse focus knob Unit used to measure microscopic objects c Stage Equipment used to make a wet mount d Objective lens The object being studied using the microscope e Micrometre f Specimen The lens of the microscope closest to the specimen The part of the microscope you look through g Mirror Used to reflect light through the specimen h Fine focus knob Used to focus the microscope on low power i Slide and coverslip Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 1 Activity 2.2 1 a Cell wall The skin that holds the cell together b Cell membrane A watery, jelly-like mixture that contains many smaller parts where the work of the cell takes place The powerhouse of the cell where the energy we need is released from the food we eat The skeleton of a plant c Nucleus d Cytoplasm e Vacuole f Mitochondria g Ribosome h Endoplasmic reticulum i Lysosome j Chloroplast 2 The garbage disposal units that get rid of wastes from the cell Part of the cell where photosynthesis takes place Control centre of the cell Contains wastes or chemicals that are being moved around the cell Microscopic factories that produce the proteins we use to grow and repair our bodies Pathways that allow materials to move quickly and easily through the cell From the top: Cell membrane; nucleus; cytoplasm; chloroplast; vacuole; cell wall Activity 2.3 1 a Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 2 2 b They would fall down into a heap. c They would remain on top of one another like a tower of bricks. It would be very easy to burst the animal cell because it is only protected by a thin cell membrane. The plant cell would be more difficult to burst because the cell membrane is protected by the cell wall. 3 a b The animal cell is most easily able to change its shape. 4 The tree would collapse to the ground. 5 The runner would not be able to move as the muscles would all become rigid and inflexible. The tissues of the joints would not be elastic. 6 a List the advantages and disadvantages of having cells like animal cells. Advantages The shape can be changed—muscles can stretch and relax. The cells are elastic to some extent and withstand some pressure without damage. b Disadvantages The body needs some form of support. The cells are easily damaged by sharp objects and abrasion. Many animals have skeletons that support the body—which may be internal or external. Some animals such as humans have an internal skeleton to support and protect our tissues and organs. Some animals have shells and external skeletons to provide protection. Antennae and other sense organs warn them of potential danger, allowing them to avoid it. 7 a List the advantages and disadvantages of having cells like plant cells. Advantages The rigid outer surface provides both protection for the internal contents and structure. There is no need for a separate skeleton. Disadvantages The cells cannot change shape and therefore movement is not possible. Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 3 b Individual plants cannot move. However, the seeds of many plants are adapted to move away from the parent plant. Activity 2.4 1 cm 0.03 0.7 0.2 0.0045 0.03 0.013 0.004 0.0078 2 3 a 3 cm b 30 µm mm 0.3 7 2 0.045 0.3 0.13 0.04 0.078 µm 300 7000 2000 45 300 130 4 78 a Question What is the diameter of the red blood cell? What is the diameter of the human cheek cell? What is the length of the cell from the leaf? What is the width of the cell from the leaf? What is the length of the onion skin cell? What is the width of the onion skin cell? What is the length of the body of the Vibrio bacterium? What is the diameter of the body of the Vibrio bacterium? What is the length of the tail of the Vibrio bacterium? What is the diameter of the Streptococcus bacterium? Measurement (cm) Scale Calculation Actual size (µm) 1 1 cm = 5 µm 1 × 5 µm 5 2.5 1 cm = 20 µm 2.5 × 20 µm 50 5.5 1 cm = 10 µm 5.5 × 10 µm 55 1.3 1 cm = 10 µm 1.3 × 10 µm 13 5.3 1 cm = 20 µm 5.3 × 20 µm 106 2.7 1 cm = 20 µm 2.7 × 20 µm 54 2 1 cm = 1 µm 2 × 1 µm 2 0.5 1 cm = 1 µm 0.5 × 1 µm 0.5 3 1 cm = 1 µm 3 × 1 µm 3 0.5 1 cm = 1 µm 0.5 × 1 µm 0.5 Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 4 b 50 ÷ 0.5 = 100 c 555 ÷ 5 = 11 Activity 2.5 1 a – Sunflower pollen b – Paper c – Eye of a fly d – Salt crystals e – Foot of a housefly f – Cotton fibres g – Tip of ballpoint pen h – Rust on a rusty nail 2 It is difficult to know how to look at the image, to make the correct parts come forward or go into the background as your brain creates the three dimensions. You cannot tell which parts are important. Early scientists did not know what was really there in a cell and what may be an artefact created by the processing of the materials for the microscope. When you look at something new you try to relate it to something familiar. However, in some situations there is nothing familiar. Activity 2.6 1 a Human skin cell: The flat shape with cells overlapping means that the cells can form a complete cover for the body with no gaps between the cells. b Nerve cell in brain: The many branching axons are able to make connections between many cells of the brain. c Nerve cell in body: The long axons mean that the nerve message can travel for long distances within the body. d Cell from small intestine: The cells have a large surface area through which food can be absorbed. Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 5 2 a The cell wall has progressively become thicker and the cell has lost its contents. b The thick cell wall would provide support for the plant as it became larger and heavier. 3 Feature of cell How the feature helps the cell do its job a Cells in the upper layers of leaves have large numbers of chloroplasts. b Muscle cells in the human leg have large numbers of mitochondria. The upper layers are exposed to the Sun. The large numbers of chloroplasts would use the Sun’s energy for photosynthesis. The muscles require energy for movement. The energy would be supplied by the mitochondria. c The cells in plant stems that carry water from the roots have no cross walls so they form a continuous tube like a drinking straw. d Cells in bone can produce a hard substance that completely surrounds them. The lack of cross walls means that the water can flow up the stem with nothing to stop it. The hard substance would add strength to the bone, making the whole skeleton stronger to support the body. Activity 2.7 1 Length of side (cm) 2 1 0.5 a b c e 24 6 1.5 g Number of cubes 1 8 64 Total surface area (cm2) 24 48 96 The surface area doubles at each stage. 0.25 0.125 f Surface area of cube (cm2) 0.375 0.09375 512 4096 192 387 Four times faster because the total surface area of 64 0.5 cm cubes is 96 cm2, and the total surface area of one 2 cm cube is 24 cm2. 96 ÷ 24 = 4. 2 They have a larger surface area, so they can absorb more water. 3 The cells shown in Figure 2.7.2b have a large surface area, so the small intestine is probably where absorption of food takes place. 4 Figure 2.7.3a would carry out gas exchange more efficiently because more of the surface area of the cells is exposed to the air pockets. Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 6 Activity 2.8 1 Growing cells separately from the organism they came from. 2 Cultured cells are used to produce vaccines that protect you from diseases; to produce anticancer agents; to produce new skin for grafting on to wounds; and to produce new organs. 3 Muscle cells can only produce new muscle cells, whereas stem cells are able to become different types of cells under special conditions. 4 The flow diagram should include the following steps: Extract cells from the bladder and extract muscle cells → Grow cells in culture solution → Place cells on the bladder-shaped shell (muscle cells to the outside; bladder cells to the inside) → Continue to grow cells for 7 weeks → Stitch new bladder into position. 5. Without the shell the cells would not form an organ of the correct shape. 6 Cells from the bladder lining and muscle cells 7 The two types of cells have different functions, both of which are essential for the functioning of the bladder. Activity 2.9 Cells crossword Answers M M E C U H O I M U C A L R G T M K L R C T I A O G Y I T R R A O N I O T S O Y O N M I C R O S C O P E E F E G P U H T L L T I L A L E O I A L R E L N A N C S E E D U L S M D R A R I A T The letters in the bolded column spell MICROSCOPE. Definition of microscope: an instrument used to make very small things look bigger. Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 7 Cells wordfind 2 S P E C I M E N A C G L B E R R E T I C U L U M L P N E N T I S S U E S F I E L D O F V I E W N B T W R O O F A M A R E T H A H P R O C U L A R C E L L L G G U N E F V L L L C A A H O S N F E U I A R S N E L O S E C V U F I M A G E L A G E D M U S I S I M F U C L O T N U C L E U S R L L Key term Cell wall Endoplasmic reticulum Epithelium Field of view Image Nerve cell Nucleus Ocular lens Organ Specimen Tissue Vacuole Definition The skeleton of the plant Pathways along which materials move through the cell Another name for skin The amount of the specimen seen through a microscope What is seen using the microscope Cells that carry information in the body. The control centre of the cell The lens of the microscope that you look through Structures that contains at least two different types of tissues that work together to complete a task The object being looked at through a microscope Groups of cells that perform the same function in the body Small structures in animal cells that may contain wastes or chemicals. Large sap-filled structures in plant cells that stores water, wastes and nutrients Copyright © Pearson Australia 2011 (a division of Pearson Australia Group Pty Ltd) ISBN 978 1 4425 2356 2 Page 8