IGCSE Biology Section 1/A

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Name and explain the eight processes of life
Movement, respiration, sensitivity, nutrition, excretion, reproduction, growth and HOMEOSTASIS. + explain
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Name the levels of organisation, starting with the smallest structure first.
Organelles < Cells < Tissues
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What are organelles and cells?
Organelles- tiny structures within the cell for example nucleus and mitochondrion. Cells- are mostly specialized to carry out a function example red blood cells for transporting oxygen.
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What are tissues, organs and organ systems?
Tissues- are when similar specialized cells group together (not necessarily the same type of cell.) Example- xylem which carries water and minerals. Organ- varying tissues working together example the lungs. Organ systems,organs work together
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Name two organelles in both animal and plant cells, and their function.
Nucleus- Most living cells have this, contains the chromosomes and thus controls the activity of the cell. Genes control which protein the cell can make. Mitochondria- Carry out respiration reactions (which releases energy.) Found in cytoplasm.
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Name another two organelles in both animal and plant cells, and their function.
Cell membrane- Is selectively permeable, controls what goes in and out of the cell. Cytoplasm- Is living material, makes up a cell. Chemical reactions happen here.
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Name three organelles, only found in plant cells.
Cell wall- made of cellulose, surrounds the membrane and provides support. Vacuole- Contains cell sap, and supports the cell. Chloroplasts- contain chlorophyll so photosynthesis happens.
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Name the six groups of living organisms
Plants, animals, fungi, virus, bacteria, protoctists.
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Explain the structure, function and characteristics of ANIMALS.
Multicellular. No cell wall. Have nervous coordination. Can move around. Store carbohydrates as glycogen.
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Explain the structure, function and characteristics of PLANTS.
Multicellular. Have chloroplasts and can photosynthesise. Their cell walls are made up of cellulose. They store carbohydrates as sucrose or starch.
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Explain the structure, function and characteristics of PROTOCTISTS.
Single celled. Some are more like plant cells with chlorophyll (algae,) some are more like animals cells (amoeba.)
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Explain the structure, function and characteristics of FUNGI.
Multi-cellular, yeasts are single celled. Mushroom/toadstool is the reproductive structure (fruiting body.) Under soil=thread like filaments (hypae,) the whole network = mycelium. Cell walls made of chitin. Carbohydrates are stored as glycogen.
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Explain the structure, function and characteristics of BACTERIA.
Single celled. Spheres, rods or spirals. cell wall (maintain structure.) Cell wall made of polysaccharides and proteins. No nucleus, single loop of DNA. Some propelled in water by flagellum. Plasmids carry genes. Decomposers, and some are pathogens.
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Explain the structure, function and characteristics of VIRUSES.
Particles not cells, not species. Smaller than bacteria. Reproduce inside host cell. DNA OR RNA SURROUNDED BY PROTEIN CAPSID, SOMETIMES SOURROUNDED BY ENVELOPE. Take over host cell's genetic machinery, host cell dies and it infects other cells.
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Explain saprophytic/saprotrophic nutrition.
Extra-cellular enzymes used. mould spores in air land on a surface. Hypae branches on food, and mycelium covers the surface. Hypae secretes enzymes onto the dead organism which breaks it down into soluable structures e.g sugar. Re-absorbed by mould.
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What is a pathogen?
Organisms that cause disease, some fungi, bacteria viruses etc.
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What are enzymes?
Biological catalysts (proteins) which speed up metabolic reactions, without being used up.
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How is it possible that there are so many types of enzymes?
Because they are proteins, and there are many combinations of amino acids, forming various proteins.
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Why are enzymes needed?
Temperatures inside organisms are low, many many reactions wouldn't take place. If you raised the temperature, unwanted reactions would speed up too.
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How do enzymes work?
The substrate joins onto the active site of the enzyme ( a small area of the surface.) This lowers the energy needed to start the reaction, meaning products can be formed more easily. The substrat has to be the right shape to fit into the active site
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How does temperature affect enzymes?
Heat energy =enzymes and substrate particles have more kinetic energy, a higher collision rate, thus the reaction is quicker. If the enzyme gets too hot, the enzyme's bonds will break, the active site will denature.The site= useless, reaction stops.
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PAPER TWO- how does pH affect enzyme activity?
Similar to temperature, if it becomes too acidic or alkaline, the bonds will break, it will denature and the active site becomes useless. This is irreversible and the reaction ceases.
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Name experiments to show the effects of temperature on enzyme activity.
measure how fast product appears. hydrogen peroxide-> oxygen and water. water displacement method, measure volume of oxygen given off in time frame. independent variable= temperature of water bath which H2O2 lies in.
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Name experiments to show the effects of temperature on enzyme activity.
measure how fast a substrate disappears. Amylase into starch and maltose. You can see if starch is present by using iodine. Therefore time how long it takes for the solution to turn back from black. Independent variable=temperature of water bath
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What is diffusion?
It can occur in liquids and gases as the particles are free to move. (when they have kinetic energy.) It is the movement of atoms from an area of high concentration to an area of low concentration. Eventually there is an equilibrium.
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How do cell membranes work?
They are semi/selectively permeable, they allow certain ions and soluble molecules through. Only small molecules e.g water, not proteins or starch.
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Explain osmosis.
The movement of WATER MOLECULES across an partially permeable membrane, from an area of high concentration (high water potential) to low concentration (low water potential.)
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PAPER TWO- What are turgid cells?
The tough cellulose cell wall around the cell keeps the shape of the cell and can resist against pressure changes. If outside the cell, there is high water potential, water will pass through the membrane=pressure in cell, pushes cell wall 'plump'
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PAPER TWO- What are flaccid and plasmolysed cells?
higher water potential in the cell, the water leaves cell by osmosis. There is less pressure in the cell, and the cytoplasm doesn't push against the wall (flaccid.) Plasmolysed is to the extent where the membrane breaks from the wall.
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What is the state of 'turgor' and why is it useful?
When many of the plant cells are turgis, it supports the less wooden parts of the plant for example the leaves. Thus leaves can photosynthesise properly. If left without water, plant will wilt and droop to expose less surface area to loose less water
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Explain active transport
The opposite of diffusion where particles move against the concentration gradient, USING ENERGY RELEASED FROM RESPIRATION. The cells use energy to pump particles through to the cell, using proteins the the cell membrane/wall.
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How to test for osmosis and diffusion.
Osmosis- potato, identical cylinders, varying sugar solutions. Measure length before and after . If longer, water gained by osmosis. Diffusion- agar jelly with phenolphalein, cubed, beaker. dilute HCl, cubes turn colourless. acid diffuses into agar.
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Card 2

Front

Name the levels of organisation, starting with the smallest structure first.

Back

Organelles < Cells < Tissues

Card 3

Front

What are organelles and cells?

Back

Preview of the front of card 3

Card 4

Front

What are tissues, organs and organ systems?

Back

Preview of the front of card 4

Card 5

Front

Name two organelles in both animal and plant cells, and their function.

Back

Preview of the front of card 5
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