Sec 1 Science Cells Sample

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www.ApexEducators.com 1 Name : _________________________ Date: _________________________ Lower Secondary Sciences: Cells 1. Cells • Cells are the basic building blocks of life. - They take in nutrients from food and convert them into energy. - They can also carry out specialised functions and reproduce. • Living organisms can be classified into unicellular (with only one cell) and multicellular (with many cells). Unicellular Multicellular Amoeba, Protozoa, Algae and Yeast Animals, Fungi and Plants • The size of animal cells and plant cells is very small, in the range of 1 to 100 micrometres (!m). They can only be visible with the help of a microscope. A) Understanding Animal Cells and Plant Cells • All animal cells do not have a cell wall. • The basic structure of a typical animal cell and a plant cell:

www.ApexEducators.com 2 • The table below shows the function for each organelle: Organelle Function Cell membrane • A semi-permeable structure which controls the movement of materials in and out of the cell Nucleus • Controls all the activities of a cell • Contains chromosomes which store heredity materials which pass from parents to offspring • Chromosomes contain many genes. which are made up of DNA. Vacuole • Contains a membrane-enclosed fluid which stores food, water and nutrients needed by the cell. Cytoplasm • Made up of jelly-like material which allows various chemical reactions to take place. Cell Wall* • Made up of cellulose which provides support and maintains regular shape of the cell Chloroplast* • Contains chlorophyll to absorb light energy for photosynthesis *only present in plant cells • In animal cells and plant cells, protoplasm (cytoplasm and nucleus) refers to the ‘living part of the cell’ that is surrounded by the cell membrane. B) Differences between an animal cell and a plant cell Organelle/Characteristics Animal cell Plant cell Cell wall Absent Present Vacuole Small but many Big but one (central vacuole) Chloroplast Absent Present Shape Irregular Regular

www.ApexEducators.com 3 2. Differentiation of Cells • In multicellular organisms, cells are specialized in performing different functions in order for organisms to coordinate and survival better. In animals Specialised cell Specialised feature and function Red Blood Cell • Contains haemoglobin to transport oxygen. • No nucleus (to make more room for haemoglobin). • Biconcave shape to maximize surface area to volume ratio for oxygen diffusion. Muscle Cell • Striated appearance. • Enable the movement of body. Sperm • Contain genetic materials (DNA) for hereditary. • Considered as haploid cells. Egg Nerve cell • Consist of basic cell body with thread-like structures. • Carry electrical messages around the body for action and reaction responses. Bone cell • Maintains the bone tissue so that the bones can support the body.

www.ApexEducators.com 4 In plants Specialised cell Specialised feature and function Root hair cell • Elongated structure to increase the surface area of the cell for absorbing water effectively • Does not contain chloroplasts as it does not carry out photosynthesis. Guard cells • Controls the pores of stomata for gaseous exchange Xylem vessel • Non-living structure that contains lumen for transporting water and mineral salts. 3. Division of labour • Division of labour refers to refers to the specialised functions of cells where cells have a particular function. This ensures the efficient and smooth functioning of the multicellular organisms so that they can survive. • The levels of organisation of cells can be summarized in the following sequence: Level Description Cell • Each cell has a specific function in the body of an organism. Tissue • A group of cells performing similar function. • Examples: Blood, muscle and skin tissue. Organ • A group of tissues performing similar functions. • Examples: Heart, liver, stomach, lungs. Organ system • A group of organs linked together to perform a particular function(s). • Examples: Digestive system, Circulatory system, Respiratory system, Organism • A group of systems working in a systematic and coordinated way to allow the organism to survive. • Examples: Animals and plants

www.ApexEducators.com 5 4. Using a Microscope* • The light microscope makes an object appear bigger by magnifying it. It is useful to see objects which are not visible to the naked eye. • The eye piece of a microscope contains the ocular lens which has a 10 times (10×) magnification and the objective lens – 3 magnifications: scanning, low and high. • Total magnification = #$%&'(')$*'+& +( +)-.$/ .0&1 × +230)*'40 .0&1 Magnification Total magnification Ocular Objective lens Scanning 10× 4× 40× Low power 10× 10× 100× High power 10× 40× 400× • The table below shows the important parts and their functions: Part Function Coarse focus knob • Focus the specimen. Fine focus knob • Fine tune the focus to give a clear image of the specimen. Eye piece • Allow the user to look through. It magnifies the specimen 10×. Objective lens • Allow the users to magnify the specimen to the greatest power. Stage • A flat platform where the slide of the specimen is placed. Mirror • Acts as light source to reflect light shining through the specimen.

www.ApexEducators.com 21 Name : _________________________ Date: _________________________ Cells (Worksheet 2) Section A: MCQ 1. What is the function of the type of cell shown in the diagram below? A. makes strong bones to support the body B. contracts and relaxes to help humans move C. transports oxygen from the lungs to the body D. removes waste materials from the cells 2. Which of the following is not a reason why humans have different types of cells in their body? A. Each type of cell can carry out specific function in the body. B. Each type of cell can take over the function of other cells in the body. C. Different types of cells need to work together to help body function efficiently. D. There is a division of labor among the different cells in the body. 3. Which row matches the part of the cell to its function? part function A B C D cell membrane cell membrane cytoplasm cytoplasm contains genetic material produces energy for the cell contains water and food materials controls all cell activities

www.ApexEducators.com 22 4. Which of the following describes the function of bone cells? A. They provide us with the flexibility of enabling movement of our bodies. B. They allow us to feel pain by sending signals to the brain. C. They transport oxygen around the body. D. They make up the structure that supports our body. 5. The purpose of the cell membrane is to: A. control activities in the cell B. control materials entering and leaving the cell C. multiply and pass genes to the next generation D. provide a medium for cell reactions to occur 6. Which specialized cell is correctly matched to its function? cell function A B C D bone cell brain cell nerve cell red blood cell sends and receives signals supports the body helps the bo