1.1 Characteristics common to organisms

Size: px

Start display at page:

Download "1.1 Characteristics common to organisms"

Moses Henderson
5 years ago
Views:

1 Biology Form 3 Page 5 Ms. R. Buttigieg 1.1 Characteristics common to organisms see GCSE Biology pg. 292 Biology is the study of living things. We call living things organisms. Plants and animals are ALL living organisms. But how do we decide if something is living or non-living? If something is alive it will carry out all these 7 life processes: 1. Feeding: - Food is needed for energy and growth. a. Plants make their own food by the process of photosynthesis. b. Animals eat plants or other animals. 2. Respiration: - This means getting the energy from the food you eat. All living things respire because they need energy. Oxygen is usually needed for respiration to happen. This energy is used for moving, growing and repairing the body. 3. Movement: - Plants move slowly when they grow. Roots move down into the soil. Stems move up towards the light. Animals move their whole bodies. They can move to get their food or avoid being caught. 4. Growth: - a permanent increase in body size. All living organisms grow. a. Plants carry on growing all their lives (mostly at the roots and shoot). b. Animals stop growing when they reach a certain size. 5. Excretion: - This means getting rid of waste produced during chemical reactions in cells. All living things produce waste. a. Plants store waste substances in their leaves. The waste is removed when the leaves fall off. b. Animals breathe out waste carbon dioxide. Other waste leaves the body in the urine and in the sweat. 6. Sensitivity: - Living organisms react to things happening around them. a. Plants will move their leaves to face the light. b. Animals have different sense organs like sight, smell, hearing etc. 7. Reproduction: - If a particular animal or plant did not reproduce it would die out. a. Plants make seeds that grow into new plants b. Animals lay eggs or have babies.

Biology Form 3 Page 6 Ms. R. Buttigieg 1.2 The Cell Houses are built up of bricks stuck together. Plants and animals are built up of cells stuck together.

There are different types of cells: E.g. All the cells have the same general plan depending on whether they are animal or plant cells.

part that cannot be observed with the light microscope is the mitochondrion.

2 Biology Form 3 Page 6 Ms. R. Buttigieg 1.2 The Cell Houses are built up of bricks stuck together. Plants and animals are built up of cells stuck together. Cells are tiny building blocks that make up living things. Some organisms are made up of just 1 cell e.g. bacteria. Other organisms like insects have millions of cells e.g. fly Human beings like you have billions and billions of cells. There are different types of cells: E.g. All the cells have the same general plan depending on whether they are animal or plant cells. cytoplasm Cell membrane Cell wall stored food Vacuole cytoplasm nucleus Chloroplast cell membrane nucleus stored food Typical Animal cell (above) Typical plant cell (right) a mitochondrion A cell part that cannot be observed with the light microscope is the mitochondrion. With a very powerful microscope the mitochondria (plural) may be observed as small dots and with still more powerful microscopes they look like the diagram on the left. Respiration happens inside a mitochondrion to release energy from food molecules. Work to do (on file paper) a. List a function of each of the following organelles (cell parts): nucleus, cytoplasm, vacuole, cell membrane, cell wall, chloroplasts, mitochondrion b. List 3 differences between plant and animal cells. c. Draw a labelled plant cell.

Cytoplasm - The liquid part filling up the cell - Contains particles called organelles, which float in it. 3.

3 Biology Form 3 Page 7 Ms. R. Buttigieg Description & Function of the main cell structures 1. Cell membrane Keeps the contents of the cell inside - Controls what substances leave or enter the cell - It is selectively permeable 2. Cytoplasm - The liquid part filling up the cell - Contains particles called organelles, which float in it. 3. Nucleus - The largest organelle in the cell - Controls all the cell activities - Contains a number of thread-like structures in it called chromosomes - Filled with a fluid called nucleoplasm 4. Mitochondrion - A lot are present in one cell. - Break down food material to provide the cell with energy - respiration - They are very small sausage shaped structure (cannot be seen with light microscope) The following are only found in plant cells 5. Cell Wall - Strong layer made of cellulose found outside the cell membrane - Non-living and substances can pass freely from it - Gives plant cells shape and makes them rigid 6. Large Vacuole - Fluid filled bubbles in the cytoplasm - Surrounded by a small membrane called tonoplast - In plants it is filled with sap containing sugars, salts, water etc. - Note that animal cells have very small vacuoles 7. Chloroplasts - Small spherical structures in the cytoplasm - Contain a green pigment called chlorophyll - Chlorophyll gives plants their green colour - The place where plants build their food from water and CO 2 (photosynthesis) The Main Differences between plant & animal cells Plant Cells Animal Cells 1. large cells smaller cells 2. cellulose cell walls not present 3. chloroplasts and chloropyll not present 4. large central permanent vacuole small, temporary vacuoles 5. nucleus is at the side nucleus usually more central 6. cells rectangular or cuboid in shape cells are round in shape 7. food is present as starch food is present as glycogen

4 Biology Form 3 Page 8 Ms. R. Buttigieg 1.3 Movement of substances in and out of cells a) DIFFUSION When a purple crystal is placed in water, it results in all the water turning purple after a couple of hours. This happens because the crystal breaks into tiny particles that spread out and fit between water molecules by diffusion. This also happens when sugar is dissolved in water. Remember: - Solution is made up of solvent (e.g. water) and solute (e.g. sugar). The solute is dissolved in the solvent. Molecules shown spreading in all directions. When food is being cooked in the kitchen you can smell it in other rooms in the house. This is because molecules are leaving the food as a gas and moving around at high speed, eventually reaching all parts of the house. This is also called diffusion. DIFFUSION is the movement of particles from a high concentration to a low concentration until they are spread out evenly. Diffusion in our body Our body cells need food and oxygen. These are carried to our cells in the blood. When blood reaches the cells, the molecules of food and oxygen diffuse out of the blood and into the cells. blood vessel blood vessel cell cell As cells use up food and oxygen they make waste: - carbon dioxide and waste chemicals. These will poison the cells if they build up. So they diffuse out of the cells into the blood.

Biology Form 3 Page 9 Ms. R. Buttigieg b) OSMOSIS A special kind of diffusion involving water molecules. It occurs when 2 solutions are separated by a partially permeable membrane.

Water molecules diffuse from a high water concentration to a lower water concentration partially permeable membrane partially permeable membrane partially permeable membrane The tiny holes in the

5 Biology Form 3 Page 9 Ms. R. Buttigieg b) OSMOSIS A special kind of diffusion involving water molecules. It occurs when 2 solutions are separated by a partially permeable membrane. OSMOSIS is the movement of water molecules from a weaker solution into a stronger solution through a partially permeable membrane. Water molecules diffuse from a high water concentration to a lower water concentration partially permeable membrane partially permeable membrane partially permeable membrane The tiny holes in the membrane allow small water molecules to pass but stop the large solute molecules. Osmosis in plant cells Osmosis is the way in which many living things like plants take up water. Water moves into plant cells by osmosis. o The plant cell membrane acts as a partially permeable membrane. o The cell sap inside the vacuole is a strong solution. o As water enters into the cell sap, the solution becomes weaker. o Water passes from the weak solution (lot of water) into a strong solution (little water) in the next cell by osmosis. weak solution strong solution As water enters the cell it swells up as water pushes against the cell wall. When it contains as much water as possible, we say it is turgid. It s like a blown up balloon. What keeps the cell from bursting with all this water? Turgid cells are important because - They give plant support They keep the plant stems upright

Biology Form 3 Page 10 Ms. R. Buttigieg Osmosis in animal cells: If animal cells are put into a weak solution they take in water and burst. E.g. When placed in water the blood cells swell up and burst (haemolysis) This does not happen in animals that have certain adaptations like the Amoeba.

Eventually the contractile vacuole becomes so full of water that it moves to the cell membrane and bursts.

They can even take in more particles against a concentration gradient.

ACTIVE TRANSPORT is the uptake of particles by cells against a concentration gradient. This process needs energy.

6 Biology Form 3 Page 10 Ms. R. Buttigieg Osmosis in animal cells: If animal cells are put into a weak solution they take in water and burst. E.g. When placed in water the blood cells swell up and burst (haemolysis) This does not happen in animals that have certain adaptations like the Amoeba. Water enters the Amoeba by osmosis but it goes into a contractile vacuole. Eventually the contractile vacuole becomes so full of water that it moves to the cell membrane and bursts. c) ACTIVE TRANSPORT Sometimes cells can take up some particles and keep them in high concentrations without letting them diffuse out. They can even take in more particles against a concentration gradient. For example although there are a lot of magnesium ions in a plant root cell compared with the soil, it still takes up magnesium by means of active transport. ACTIVE TRANSPORT is the uptake of particles by cells against a concentration gradient. This process needs energy. outside cell outside cell cell membrane cell membrane inside cell inside cell Carrier proteins use energy (from respiration) to transport molecules or ions across the membrane. Sugars can be absorbed from the intestine and from the kidney tubules by active transport. Magnesium ions are absorbed into the root hair cell by active transport.

7 Biology Form 3 Page 11 Ms. R. Buttigieg Diffusion, osmosis and active transport compared Diffusion Osmosis Active Transport Random movement From higher to lower concentration Along the concentration gradient No energy needed from the cell Remember: Random movement of water Selective movement From higher to lower concentration Along the concentration gradient No energy needed from the cell From lower to higher concentration Against the concentration gradient Energy needed from the cell Molecules move in all directions in diffusion and osmosis. Osmosis is the diffusion of water. Diffusion continues even after the particles have spread out equally. Even when a system is in equilibrium movement of particles continues, with as many particles leaving as are arriving in any one place. In diffusion and osmosis molecules move by kinetic energy alone. In active transport, metabolic energy (energy made by respiration in the cells) is required. GCSE Biology relevant pages for this topic Chapter 1 - pages pages 9-10 (practical work) Chapter 4 - pages pages (Practical work)

8 Biology Form 3 Page 12 Ms. R. Buttigieg Answer the following Questions: - 1. Give the meaning of the following terms in the space below: (8 marks) Osmosis Diffusion Active Transport Give 1 example of the occurrence of active transport in: o Plant cells o Animal cells 2. Fill in: (10 marks) Molecules move from a concentration to a concentration by. Osmosis is the movement of molecules from a solution into a solution across a permeable membrane. When plant cells take up water by osmosis they become. Turgid cells help support parts of a plant like the. If plant cells lose water the stem lacks support and. 3. Answer the following: (10 marks) (a) Which diffuses faster, a liquid or a gas?. Why is this? (b) What would heating do to the rate of diffusion of a salt crystal in water? (c) What things diffuse Into cells (d) What things diffuse Out of cells (e) Is a cell membrane permeable, impermeable or partially permeable? (f) Is a cell wall permeable, impermeable or partially permeable? (g) Some plant cells are put into a solution. They neither take up water nor lose water. What can you say about the strength of the cell sap and the external solution?

CELLS. Structure and Function

CELLS. Structure and Function CELLS Structure and Function Cell Structure All plant and animal tissue consist of cells. Cells are microscopic in size. In general, each cell performs all the characteristics of life and, though in reality