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Transcript
Cells – the building blocks of life What is a cell? • Basic unit of all living things • Fully alive • Capable of reproduction and respiration* • Many chemical reactions take place within the cell • Contains the elements carbon, hydrogen and oxygen Trivia: How did the cell get its name? • Robert Hooke • 1665 – used the 1st microscope ever invented to look at a thin piece of cork • Box-like cells reminded him of the cells of a monastery • What he actually saw were the cell walls in cork tissue Cells from cork tissue of tree bark Visualising Cells • Cells are very small • Largest cell in the human body – human egg 0.1 mm Unicellular organisms • Uni – “one” • Living things that are only made up of one cell yeast paramecium amoeba bacteria Multicellular organisms • • • • Multi – “many” Plants Animals Human adult – 10 trillion cells! – Are all the cells the same? – Different sizes, shapes, functions – Certain similar characteristics Typical animal cell ** Nucleus Cytoplasm Cell membrane Vacuoles Is it THAT simple? Structure of an Animal Cell Animal cell Typical animal cell ** Nucleus Cytoplasm Cell membrane Vacuoles • Nucleus – Controls all chemical reactions and activities in the cell, including reproduction and cell repair – Contains chromosomes Sidetrack: Chromosomes • http://www.youtube.com/watch?v=eOvMNOMRRm8 nucleus chromosomes genes on a chromosome each chromosome is made up of many genes; each gene contains instructions for a different feature of an organism Sidetrack: Chromosomes • Found in the nucleus • Made of DNA (deoxyribonucleic acid) and proteins • Contains genes – chemical instructions to build the cell and control its functions • Genes are passed down from 1 generation to another hereditary Human cells have 23 pairs of chromosomes except the sperm and the egg (23 individual chromosomes) Sex chromosomes Genetic Diseases • Down’s Syndrome – Extra chromosome in each cell in his/her body – 47 chromosomes instead of 46 chromosomes – Result of unusual cell division when egg/sperm was made, or during fertilisation – Happens by chance, can happen to anyone Typical animal cell ** Nucleus Cytoplasm Cell membrane Vacuoles • Cell membrane – Thin layer around the cell – Allows shape of cell to change – Partially permeable, controls movement of materials in and out of the cell – Carbon dioxide, oxygen, water can pass through Typical animal cell ** Nucleus Cytoplasm Cell membrane Vacuoles • Cytoplasm – jelly-like substance that fills the cell – contains water and many other substances – chemical reactions take place here Typical animal cell ** Nucleus Cytoplasm Cell membrane Vacuoles • Vacuoles – small spaces in the cytoplasm containing water, food, waste materials etc – small and numerous in animal cells Typical plant cell ** Vacuole Chloroplasts Nucleus Cytoplasm Cellulose cell wall Cell membrane Functions similar to that of an Animal Cell Plant cell Typical plant cell ** Vacuole Cytoplasm • Vacuole − Single large vacuole − Biggest part of the cell − Filled with cell sap (contains substances such as sugars and salts dissolved in water) − Cell sap keeps the cell firm by taking in water Typical plant cell ** Vacuole Cytoplasm • Vacuole − When the plant loses water, plasmolysis occurs Click here to find out more Typical plant cell ** Vacuole Cytoplasm • Cytoplasm − Reduced to a thin lining − Still contains water and other substances, still a place for chemical reactions Typical plant cell ** • Chloroplasts Chloroplasts Cellulose cell wall – Tiny disc-like structures containing a green pigment called chlorophyll – Chlorophyll traps light energy from the sun so that plants can make food during photosynthesis – Absent in animal cells Typical plant cell ** • Cellulose cell wall – Surrounds the plant cell Chloroplasts Cellulose cell wall – Supports the plant cell and gives it a regular shape – Absent in animal cells Sidetrack: Cellulose • Compound containing carbon, hydrogen and oxygen • A type of fibre – Dietary fibre present in fruits and vegetables – Manufacture of cardboard and papers (from wood pulp) Animal Cell Plant Cell Does it have a cellulose cell wall? No Yes Does it have a cell membrane? Yes Yes Does it have a nucleus? Yes Yes Does it have cytoplasm? Yes – it fills the cell Yes – a thin lining only Does it have vacuoles? Yes – many, but small Yes – one, or a few, and large Does it have chloroplasts? No Present only in cells of green plants Shape? Can change Regular (doesn’t change)