SNAB - Biology - Topic 1

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  • Created by: Katherine
  • Created on: 18-05-15 11:27
What is the purpose of the heart and circulation?
To move substances around the body.
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In very small organisms, how are substances moved?
They are moved by diffusion.
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What is diffusion?
Diffusion is the movement of molecules or ions from a region of their high concentration to a region of their low concentration by relatively slow random movement of molecules.
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Why don't all organisms rely on diffusion?
Most complex multicellular organisms are too large for diffusion to move substances around their bodies quickly enough. These animals have bloood instead.
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What is an open circulatory system?
It is where blood circulates in large open spaces. A simple heart pumps blood out into cavities surrounding the animals organs. Substances diffuse between blood and cells. When the heart muscle relaxes, blood is drawn from the cavity back to heart.
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What is a closed circulatory system?
Blood is enclosed within tubes. This generates higher blood pressures as the blood is forced along fairly narrow channels instead of flowing into large cavities. This means that blood travels faster and the system is more efficient.
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What is a single circulatory system?
This is found in fish. The blood flows through the heart once for each complete circuit of the body.
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What is a double circulatory system?
The right ventricle of the heart pumps deoxygenated blood to the lungs where it recieves oxygen. The oxygenated blood then returns to the heart to be pumped a second time to the rest of the body. Blood flows through the heart twice.
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Mammals with double circulatory systems have higer metabolic rates than those with single. Why?
The heart gives the blood returning from the lungs an extra boost, which reduces the time taken for blood to circulate around the whole body. Oxygen and food substance required for metabolic processes are delievered more rapidly.
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Why do only small animals have an open circulatory system?
Movement of oxygen; carbon dioxide and other products carried by blood relies on diffusion in animals with open circulatory systems. Diffusion is only fast enough for small organisms.
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What are the advantages of having a double circulatory system?
Blood can pass slowly through the region where gaseous exchange takes place; maximising the transfer of oxygen and carbon dioxide; and then be pumped around the rest of the body; enabling the organism to be active.
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What might be the major disadvantage of a three chamber system, such as that found in a frog?
There could be some mixing of oxygenated and deoxygenated blood in the ventricle.
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What are the components of blood?
Plasma (composed of water and contains dissolved substances such as food, oxygen and carbon dioxide), proteins, amino acids, salts, enzymes, hormones, antibodies, urea and cells.
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What are the properties of water that make it an ideal transport medium?
It is a polar molecules with an unevenly distributed electrical charge. Due to this, hydrogen bonding can occur. Hydrogen bonding gives water solvent properties and many chemicals dissolve in water. It has a high specific heat capacity.
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What is the name of the valve between the aorta and the left ventricle?
The semilunar valve
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What is the name of the tube that delivers blood to the right atrium?
The vena cave (superior and inferior)
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What is the name of the thing that separates the two ventricles?
The septum
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Do veins or arteries deliver oxygenated blood to the heart?
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What are the features of a vein?
Wide lumen, thin walls, valves, less collagen & smooth muscle & elastic fibres
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What are the features of an artery?
Narrow lumen, thick walls, no valves, more collagen & smooth muscle & elastic fibres
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What are the features of a capillary?
Thin walls, about 1 cell thick, very narrow.
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How does blood move through the vessels?
Atrial systole, Ventricular systole, Diastole
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What is atrial systole?
Blood is forced into the ventricles as the atria contract.
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What is ventricular systole?
Contraction of the ventricles pushes blood into the arteries
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What is diastole?
The atria and ventricles relax. Elastic recoil as the heart relaxes causes low pressure in the heart, helping to refil the chambers with blood from the veins, closing the semilunar valves.
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What is the role of valves?
To prevent the backflow of blood.
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What is atherosclerosis?
It is the disease that leads to coronary heart disease and strokes. Fatty deposits can either block an artery directly, or increase its chance of being blocked by a blood clot (thrombosis). The blood supply can be blocked completely.
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What happens if the blood supply is blocked completely?
If this happens for a long time, the affected cells are permanently damaged. In the arteries supplying the heart this results in a heart attack (myocardial infarction), in the arteries supplying the heart, this results in a stroke.
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What happens in atherosclerosis?
The endothelium is damaged/ inner lining is breached. Inflammatory response, white blood cells leave the blood vessel and move into the artery wall. These cells collect chemicals from the blood. Calcium salt + fibrous tissue build up at site = plaque
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Why is the plaque harmful?
Plaques cause the artery to become narrower. This makes it more difficult for the heart to pump blood around the body and can lead to a rise in blood pressure. Now there is a dangerous positive feedback building up.
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Why is the formation of plaques an example of positive feedback?
Plaques lead to raised blood pressure and raised blood pressure makes it more likely that further plaques will form.
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Why does blot clot in arteries?
Platelets in contact with damaged wall, change from flat discs to spheres + projections. Stick to exposed collagen and to each other, forming platlet plug. Contact of blood with collagen triggers cascade of changes to form mesh.
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What is the cascade of changes that leads to the formation of a tangled mesh?
Prothrombin is converted into thrombin. Thrombin is an enzyme that catalystes the conversion of another soluble plasma protein, fibrinogen, into long insoluble strands of fibrin, a protein. These fibirn form a tangled mesh, trapping blood cells =clot
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Why do only arteries get atherosclerosis?
The fast flowing blood in arteries is under high pressure so there is a significant chance of damage to the walls. The low pressure of veins means that the is less chance of damage to the walls.
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What is the consequence of atherosclerosis?
Coronary heart disease and a stroke
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What are the symptoms of coronary heart disease?
Shortness of breath and angina. Symptoms of angina include intense pain in the chest, a burning feeling ect. Sometimes coronary heart disease causes the heart to beat irregularly (arrhythmia)
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What are the symptoms of a stroke?
Numbness, dizziness, confusion, slurred speech, blurred or lost vision. Visible signs include paralysis of one side of the body.
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What is an aneurysm?
If part of an artery has narrowed and become less flexible, blood can build up behind it. The artery bulges as it fills with blood and an aneurysm forms.
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What is the definition of risk
The probability of occurrence of some unwanted event or outcome.
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Risk question: 19429 people in the UK died due to injuries. The total UK population was 60209408, so what is the average yearly risk of someone dying from injuries?
19429 in 60209408. 19429/60209408 x 100 = 0.032%
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People will overestimate the risk of something happening if the risk is:
Involuntary (not under their control), not natural, unfamiliar, dreaded, unfair, very small
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There are many different factors that contribute to health risks, such as:
Heredity, physical environment, social environment, social environment, lifestyle and behaviour choices.
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What is correlation?
Two variables are said to show a correlation (to be correlated) if there is either a positive or a negative relationship between them.
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What is causation?
Causation means that a change in one variable results in a change in another variable. For example, during childhood there is a causal link between age and such variables as height, physical strength and vocabulary acquisition.
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What is a null hypothesis?
A useful starting point used when looking at the results of a scientific investigation. A null hypothesis assumes that there are no differences between sets of observations. A statistical test can then be used.
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What is a cohort study?
A study where a group of people are followed over time to see who develops the disease.
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What is a case-control study?
A group of people who have the disease are compared with a group who do not have the disease.
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What are the features of a good study?
Clear aim, representative sample, valid and reliable results.
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What are the risk factors of CVD?
High blood pressure, obesity, blood cholesterol and other dietary factors, smoking, genetic inheritance.
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What is hypertension?
High blood pressure
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What is blood pressure?
Blood pressure is a measure of the hydrostatic force of the blood against the walls of a blood vessel. The pressure is highest during systolic pressure. Pressure is at its lowest in the artery during diastolic pressure.
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What equipment is used to measure blood pressure?
A sphygmomanometer is a traditional device used to measure blood pressure.
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What are the two readings gathered when blood pressure is taken?
A pressure reading is taken when the blood first starts to go through the artery that has been closed (systolic pressure). A second reading is taken when the pressure falls to the point where no sound can be heard in the artery (diastolic pressure)
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What determines your blood pressure?
Contact between blood and the walls of the blood vessels causes friction, and this impedes the flow of blood. This is called peripheral resistance. The arteries and capillaries offer a greater total surface area, resisting flow more, slowing blood.
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One sign of high blood pressure is...
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What is an oedema?
Fluid building up in tissues and causing swelling. It may also be linked with kidney or liver disease or restricted body movement.
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How is tissue fluid formed?
At the arterial end of a capillary, blood is under pressure. This forces fluid and small molecules normally found in plasma out through the capillary walls into the intercellular spaces, forming tissue fluid.
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What effect does increased blood pressure have on the tissue fluid?
With increased blood pressure, more fluid may be forced out of the capillaries. In some circumstances, fluid accumulates within the tissue causing oedema.
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What types of food store energy?
Lipids, carbohydrates and proteins
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What is a carbohydrate?
'Hydrated Carbon'. Most people are familiar with sugar and starch being classified as carbohydrates but the term covers a large group of compounds with the general formula Cx(H2O)n.
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What is a monosaccharide?
A single sugar unit
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What is a disaccharide?
Two single sugar units joined together, in a condensation reaction.
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What is a polysaccharide?
Long straight or branched chains of sugar units.
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What are the names of the 3 main monosaccharides?
Fructose, Glucose & Galactose.
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Where are monosaccharides commonly found?
Glucose and Fructose are found naturally in fruits, veg and honey. They proivde a rapid source of energy, are readily absorbed and require little or energy.
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What is produced in a condensation reaction between to monosaccharides?
A disaccharide and H2O
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What is the name of the link formed in a condensation reaction?
A glycosidic link/bond.
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What monosaccharides form sucrose?
Fructose + Glucose
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What monosaccharides form maltose?
Glucose + Glucose
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What monosaccharides form Lactose?
Galactose + Glucose
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What is the reaction used to break glycosidic bonds?
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What are the three main polysaccharides?
Found in plants: starch & cellulose, found in animals: glycogen
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What is starch made from?
Amylose and amylopectin
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What is amylose?
Amylose is composed of a straight chain of glucose molecules with 1,4 glycosidic links between adjacent glucose molecules. The position of the bonds causes the chain to coil into a spiral shape.
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What is amylopectin?
It is a polymer of glucose but it has side branches. A 1,6 glycosidic link holds each side branch onto the main chain, and it also has 1,4 glycosidic links.
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What makes starch a good storage molecule?
The compact structure of starch and its insoluble nature. It does not diffuse across cell membranes and has very little osmotic effect within the cells.
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What is glycogen?
Bacteria, fungi and animals store glycogen instead of starch. Glycogen is another polymer composed of glucose molecules. Its numerous side branches mean that it can be rapidly hydrolysed, giving easy access to stored energy.
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Card 2


In very small organisms, how are substances moved?


They are moved by diffusion.

Card 3


What is diffusion?


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Card 4


Why don't all organisms rely on diffusion?


Preview of the front of card 4

Card 5


What is an open circulatory system?


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