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Structures and functions in living organisms. Revision Notes

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´╗┐Structures and functions in living organisms 2.1 Describe the levels of organisation within organisms: Organelles -> Cells -> Tissues -> Organs -> Organ Systems. Smallest ------------------------------------------->Largest 2.2 Recognise cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole 2.3 Describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole Nucleus ? The largest organelle in the cytoplasm. This controls the cell. It contains chromosomes which carry genes. Cytoplasm ? The living material that makes up a cell. It is made up of many structures called organelles. Cell Membrane ? This is a thin layer on the surface of the cell. It is a partially permeable membrane between the cytoplasm and the outside as it controls which substances pass in either direction. Cell Wall ? This is a layer found outside the cell membrane. It is freely permeable so anything can pass through it. It is responsible to maintain Plant Turgor (the plant?s shape) Chloroplast ? These absorb light energy to make food in the process of photosynthesis Vacuole ? This is filled with cell sap, a store of dissolved sugar and solutes to provide energy for the plant, until it can create its own. 2.4 Describe the differences between plant and animal cells. Plant cells have a cell wall to maintain plant Turgor, whereas animal cells do not have this Plant cells have chloroplasts in order to carry out photosynthesis, whereas animals do not have this Plant cells have a large permanent vacuole, whereas plant cells do not have this. 2.5 Recall the chemical elements present in carbohydrates, proteins and lipids (fats and oils) Carbohydrates - Carbon, Hydrogen, Oxygen Proteins - Carbon, Hydrogen, Oxygen, Nitrogen (Sulphur in two amino acids) Lipids - Carbon, Hydrogen, Oxygen 2.6 Describe the structure of carbohydrates, proteins and lipids They are large molecules made up from smaller basic units: Carbohydrate (starch and glycogen) ...read more.


After 10-15 minutes, the indicator in the covered dish would turn from red to yellow, showing an increase in carbon dioxide because photosynthesis has not occurred. The indicator in the bright light petri dish would turn from red to purple as there would be less carbon dioxide since it is being used up by photosynthesis at a faster rate than it is being produced by respiration 2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes Air enters through the nose and mouth, travelling down the trachea. The trachea then sub divides into bronchi, which further subdivide into bronchioles, which lead to tiny air sacs where gas exchange takes place calls alveoli. Pleural membranes surround the lungs, an inner one attached to the lung surface, an outer one attached to the thoracic wall. Ribs protect the organs underneath, namely the heart and lungs; the ribs are joined together by intercostals muscles. The diaphragm is a large sheet that attaches to the thorax and sits underneath the lungs 2.45 understand the role of the intercostal muscles and the diaphragm in ventilation Inhalation - Diaphragm contracts and flattens in shape. External intercostals muscles contract, making the ribs move upwards and outwards These cause the volume of the thorax to increase, causing pressure to decrease, drawing air into the lungs Expiration - Diaphragm relaxes and returns to its dome shape. External intercostals muscles relax, allowing the ribs to move down and in. These cause the volume of the thorax to decrease and the pressure to increase, forcing air out of the lungs. 2.46 Explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries * Walls are one cell thick, distance over which diffusion takes place is minimum * Moist lining, so the gases dissolve before they cross * A large surface area * High concentration gradient for gases, due to good blood supply 2.47 Understand the biological consequences ...read more.


Describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation Sweat is released on to the surface of the skin. The evaporation of this sweat needs heat energy, which it takes from the skin thus cooling the body down. If you are hot, vasodilation will occur; blood will travel in capillaries closer to the skin and these capillaries will get wider so more heat energy from the blood will be radiated from the skin I you are cold, vasoconstriction will occur; blood will travel through deeper vessels, which will be thinner preventing heat loss through radiation. Shivering may occur - rapid small contractions, which require energy from respiration, releasing heat energy at the same time. Body hair may be raised on the skin by hair erector muscles to trap a layer of warm air around the skin 2.90 Understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen. ADH - Produced in pituitary gland - causes the walls of the collecting duct to beome more/less permeable to water depending on water levels in the blood. Insulin - Produced in the pancreas - Controls blood sugar levels - It converts excess glucose into glycogen, which is insoluble and stored in the liver. When there is not enough glucose in the blood, the pancreas secretes glucagon which turns glycogen back into glucose Adrenaline - Produced in the adrenal glands - Prepares the body for fight or flight, the crucial moment when an animal decide whether to fight or run for its life. Some of the effects of adrenaline are faster pulse, increased sweating, hair standing on end (to appear larger), paling of the skin (blood shunting) Testosterone - Secreted in the testes - Male sex hormone, which causes secondary sexual characteristics in boys and is needed for the production of sperm. Progesterone and Oestrogen - Oestrogen is responsible for secondary sexual characteristics in girls and together with progesterone it controls the menstrual cycle. ...read more.

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