2009 Marshall Cavendish International Singapore Private Limited Questions

Questions to think about… What are the different parts of a plant cell and

Cells • All living things are made of cells. • A cell is the

Cells • We can look at cells and study them with the help of

Cells • Some living things are made of fewer cells, like certain algae, mosses

Cells • Some other living things are made up of only one cell. •

Different types of cells • Plants are made up of cells too. • There

Different types of cells • Some cells in a leaf make food for the

Different types of cells • Some cells in the stem transport food and water

Non-living things • Unlike living things, non-living things do not have cells. © 2009

Different types of cells • What is inside a typical animal cell? Nucleus Cytoplasm

Different types of cells • What is inside a typical plant cell? A plant

Different types of cells • What is inside a typical plant cell? Sap wall

Different types of cells • Cells come in different shapes and sizes. • Different

Different types of cells • Other cells such as red and white blood cells

Producing new cells • Our bodies increase in size as we grow. • This

Producing new cells • Single-cell organisms, such as paramecium, yeast and bacteria, multiply by

Producing new cells • Cells do not live forever. • Old cells die and

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Questions to think about… What are the different parts of a plant cell and an animal cell and what are their functions? What forms the basic unit of life? How is an animal cell different from a plant cell? What are the different types of cells? How do cells produce new cells? © 2009 Marshall Cavendish International (Singapore) Private Limited

Cells • All living things are made of cells. • A cell is the smallest unit of life in the body. • Most living things like people, cows and trees are made up of millions of cells. © 2009 Marshall Cavendish International (Singapore) Private Limited

Cells • Some other living things are made up of only one cell. • These are single-cell organisms, such as bacteria, yeast and paramecium. • The cells can only be seen under a microscope. paramecium bacteria yeast © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • Plants are made up of cells too. • There are cells in all parts of a plant – the leaves, the stem, the roots. © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • Some cells in a leaf make food for the plant. • These cells contain chlorophyll. • Chlorophyll traps light energy from the Sun to allow plants to carry out photosynthesis. • There also cells that control the size of the stoma cells in a leaf © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • Some cells in the stem transport food and water within the plant. • The xylem and phloem tubes are made up of such cells. xylem phloem cells in a stem © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • What is inside a typical animal cell? Nucleus Cytoplasm Cell membrane • In Allboth Surrounding cellsplant is made the andcytoplasm up animal of a jelly-like is cells, a soft there and substance isthin a nucleus cell called the cytoplasm. membrane. found in the cytoplasm. • The nucleus cytoplasm cell membrane is a allows very holds substances the important cytoplasm part such of inside aascell. food it. oxygen to move around • and It controls also controls everything substances that within cells. that gothe happens ininside or out the of acell. • Many activities of the cells take place in the cytoplasm © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • What is inside a typical plant cell? A plant cell has cytoplasm, a cell membrane, and nucleus, just like the animal cell. o However, a plant cell has other parts that are not found in an animal cell. o nucleus cytoplasm cell membrane © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • What is inside a typical plant cell? Sap wall Chloroplast Cell • • A fills cavity chloroplast is athe A liquid plantwhich cell has a tiny cell in the centre of most plant green structure that is wall outside the cells. found in the cytoplasm of a membrane. • The plantsap cell. keeps the cell firm. • • The cell wall is made up Firm cells helpcontain the plant to Chloroplasts of a stiff material thatdo stand upright plants chlorophyll, aas pigment that gives a plant cell system its not have a skeletal to traps sunlight for provide support. shape. photosynthesis. • • Animal cellsare do not have Cell walls not found Chloroplasts are not such cavities in them. present in animal cells. © 2009 Marshall Cavendish International (Singapore) Private Limited

Different types of cells • Cells come in different shapes and sizes. • Different types of cells have different functions. • In the human body, cells work in groups, like those in the heart and the brain. • They form the organs in the body. a brain cell heart muscle cells © 2009 Marshall Cavendish International (Singapore) Private Limited

Producing new cells • Our bodies increase in size as we grow. • This is due to an increase in the number of cells in the body. • Cells increase in number by dividing themselves. • The nucleus and cytoplasm of one cell divide to produce two cells. • The two new cells later divide into four cells. • These four cells can divide to form more cells. • This process is known as cell division. • It takes place all the time to allow cells to multiply. cell division © 2009 Marshall Cavendish International (Singapore) Private Limited

Producing new cells • Single-cell organisms, such as paramecium, yeast and bacteria, multiply by cell division. • The new cells produced are identical to the original cell. • Yeast multiplies by a special cell division method called budding (see below). In budding, a small bud grows from a yeast cell. o The bud slowly increases in size and then breaks away. o bud growing © 2009 Marshall Cavendish International (Singapore) Private Limited

Producing new cells • Cells do not live forever. • Old cells die and new ones are produced to replace them. • This takes place in our bodies all the time. • Our skin cells can live for 3 weeks while the cells lining out intestines are replaced after 3 days. • Some cells also divide to help repair damaged parts of our bodies. © 2009 Marshall Cavendish International (Singapore) Private Limited