Transcript Cells
Cells 1 of 31 © Boardworks Ltd 2011 2 of 31 © Boardworks Ltd 2011 Where in the world? How does a cell resemble a city? 3 of 31 © Boardworks Ltd 2011 What is a cell? A cell is the basic unit of life, from which larger structures such as tissue and organs are made. Unicellular organisms, such as bacteria, consist of just a single cell. Multicellular organisms consist of many cells – humans are made from an estimated 50 trillion cells! 4 of 31 © Boardworks Ltd 2011 How big is a cell? Most plant and animal cells are between 10 µm and 100 µm in size – around the diameter of a human hair – and too small to see without a microscope. The largest cell in the human body is the female egg cell, (ovum) at around 100 µm in diameter. The smallest human cell is the sperm cell – the head is around 5 µm long. 5 of 31 © Boardworks Ltd 2011 Comparing micro-organisms 6 of 31 © Boardworks Ltd 2011 Microscopes Thanks to advances in microscope technology, we can see micro-organisms with far greater detail and clarity than was possible in the past. magnification = size of image actual size of the object When Antonie van Leeuwenhoek discovered singlecelled organisms in 1676, his microscope could magnify an image up to 500 times. Now, with the use of electron microscopes, scientists can attain a magnification as high as 2×106. 7 of 31 © Boardworks Ltd 2011 Specialized cells Most plants and animals are multicellular. The human body is made up of around 200 different types of cell, all working together. Most cells are specialized, meaning that each type of cell has a specific structure and function. All cells with a nucleus contain the same genes, but different cells activate different genes so they only produce the proteins they need. However, all cells have certain common features and structures called organelles. 8 of 31 © Boardworks Ltd 2011 What do cells contain? 9 of 31 © Boardworks Ltd 2011 Animal or plant? 10 of 31 © Boardworks Ltd 2011 Microbial cells 11 of 31 © Boardworks Ltd 2011 Bacteria Unlike other cells, bacteria have no distinct nucleus. Instead, their genetic material is contained within a coiled cluster of chromosomal DNA and a single circular strand of plasmid DNA. Plasmid DNA can reproduce independently of chromosomal DNA, and can be transferred to other cells. Bacteria also lack mitochondria and chloroplasts. Some bacteria have one or more flagella, which are used for locomotion. 12 of 31 © Boardworks Ltd 2011 13 of 31 © Boardworks Ltd 2011 A closer look at animal cells 14 of 31 © Boardworks Ltd 2011 Exploring animal cells 15 of 31 © Boardworks Ltd 2011 How are animal cells adapted? 16 of 31 © Boardworks Ltd 2011 Animal cells: fit for a purpose 17 of 31 © Boardworks Ltd 2011 18 of 31 © Boardworks Ltd 2011 A closer look at plant cells 19 of 31 © Boardworks Ltd 2011 Exploring plant cells 20 of 31 © Boardworks Ltd 2011 How are plant cells adapted? 21 of 31 © Boardworks Ltd 2011 Plant cells: fit for a purpose 22 of 31 © Boardworks Ltd 2011 What is a cell wall? All plant cells have a cell wall – a rigid layer that surrounds the cell membrane. The plant cell wall is made from cellulose, a carbohydrate polymer. The purpose of the cell wall is to: maintain the shape and structure of the cell protect the cell’s contents from pathogens prevent damage to the cell caused by excess water intake. Unlike the cell membrane, the cell wall is freely permeable to water and other molecules. 23 of 31 © Boardworks Ltd 2011 What is a vacuole? The vacuole is a fluid–filled sac found within plant cells and some bacteria. The vacuole has a range of functions, including: storing waste products maintaining the water and pH balance of the cell maintaining the shape of the cell. The size of vacuoles depend on how much water the plant has absorbed. 24 of 31 © Boardworks Ltd 2011 What are chloroplasts? Chloroplasts are the site of photosynthesis in plant cells. A green pigment in chloroplasts called chlorophyll absorbs the energy in sunlight. This energy is used to convert carbon dioxide and water into glucose and oxygen. 25 of 31 © Boardworks Ltd 2011 Which organelle? 26 of 31 © Boardworks Ltd 2011 Make a cell model You can make your own 3-D cell using the following items: a plastic bag clear gelatin small objects to suspend in the cellulose paste (these will represent the internal structures of the cell). Can you make a model of a typical plant or animal cell? 27 of 31 © Boardworks Ltd 2011 28 of 31 © Boardworks Ltd 2011 Glossary 29 of 31 © Boardworks Ltd 2011 Anagrams 30 of 31 © Boardworks Ltd 2011 Multiple-choice quiz 31 of 31 © Boardworks Ltd 2011