GCSE Biology B2 (OCR)

Frage	Antworten
What are the symptoms of an infectious disease caused by?	Damage done to cells by microogranisms or the toxins (poisins) they produce.
Why can microorganisms reproduce rapidly in suitable conditions?	Because they have enough nutrients, moisture and warmth to reproduce.
What are white blood cells, and what do they do?	White blood cells are part of the body's immune system. They can destroy microorganisms by engulfing them or by producing antibodies, which attach to antigen markers on microorganisms.
Explain antigens.	Antingens are on the outisde of each microorganism, and they are unique to that type. A different antibody is needed to recognise each antigen.
Why are memory cells useful?	Because they recognise antigens which have been in your blood before, and they remember the antibody which is needed to mark it. It can then reproduce very quickly and make the antibody which is required.
How do vaccinations provide protection from microorganisms?	They encourage white blood cells to proudce antibodies to stick to the microorganisms. The memory cell then remembers these, so if the microorganism invades again they can produce the right antibody very quickly. Therefore, the microorganisms are destroyed before they can make you ill.
What does a vaccine usually contain?	A safe form (dead, partial or inactive) of a disease-causing microorganism.
Why is it necessary to vaccinate a high percentage of the population to prevent epidemics of infectious diseases?	If they are not, then large numbers of the disease-causing microorganisms will be left in infected people.
Why can't vaccines and medicines be completely risk-free?	They have varying degrees of side effects to them.
Why do people react differently to medicines and vaccines?	People are genetically different, so they react differently to medical treatments.
What can antimicrobials be used for?	They can be used to kill, or inhibit bacteria, fungi and viruses.
What are antibiotics?	A type of antimicrobial that are effective against bacteria but not against fungi and viruses.
What can lead to varieties which are less effected by antimicrobials?	Mutations in the genes.
Why may bacteria and fungi become resistant to antimicrobials?	Mutations in the bacteria made them resistant to antimicrobials. Only resistant bacteria survived the medicine. They then reproduced so the whole population was resistant.
What can be done to reduce antibiotic resistance?	Only use antibiotics when necessary, always complete the course, have better hygiene in hospitals to reduce infection.
How are new medicines first tested for safety?	Using human cells grown in the laboratory, and then using animals.
What are the two stages to human trials?	Healthy volunteers : To test for safety. People with the disease: To test for effectiveness and safety.
What is the difference between 'open-label', 'blind', and 'double-blind' human trials? Why are these used?	Open-Label: Both patent and doctor know the treatment. It's used if there is no other treatment. Blind: The docotr knows but not the patient. It's used when the doctor needs to check for unwanted side effects. Double-Blind: Neither patient nor doctor know. It's used because it could effect the way they report symptoms.
What is the importance of long-term human trials?	It is needed to find out if a new drug has real benefits, and whether it has any risks.
What are the ethical issues related to using placebos during human trials?	A real drug might increase the chances of recovery.
Describe the role of the heart as a d____ p___ in the circulatory system.	Double Pump. Blood flows in the right hand side of the heart, flows into the right lower chamber and gets pumped into the lungs to pick up oxygen. It then flows into the left upper chamber , and then into the left lower chamber. From there, it is pumped to the rest of the body to deliver oxygen.
Why do heart muscle cells need their own blood supply?	Because blood brings oxygen and food to cells. Cells use these as a supply of energy. Without energy, the cells would start to die and the heart would stop. This is a heart-attack.
What is the structure of arteries, veins, and capillaries? How are they suited to their functions?	Arteries: Thick outer wall (withstand high pressure created by pumping heart), thick layer of muscle, elastic fibres. They take blood from the heart to the body. Veins: Thick layer of muscle and elastic fibres (allows the vein to be squashed when you move), valves (stop the blood flowing backwards). Veins bring blood back to the heart. Capillaries: One-cell-thick wall (allows diffusion of oxygen and food to the cells and waste from the cells). They take blood to and from the tissues.
How can heart rate be measured?	By recording the pulse rate.
What do blood pressure measurements record?	The pressure of the blood on the walls of the artery.
How is a blood pressure measurement given?	As two numbers. Higher value = When the heart is contracting. Lower value = When the heart is relaxed.
Why are 'normal' measurements for heart rate and blood pressure given within a range?	Because individuals vary.
How can fatty deposits in the blood vessels supplying the heart muscles produce a heart attack?	A blood clot can form on the fatty deposit. It starves the muscle of oxygen, so the cells start to die.
What is heart disease caused by?	Lifestyle choices and genes. Eg. Poor diet, stress, smoking, misuse of drugs.
What can reduce the risk of heart disease?	Regular moderate exercise, drinking alcohol in moderation, reducing stress.
How are factors which effect the risk of heart disease identified?	Via epidemiological and large scale genetics studies.
Why does high blood pressure increase the risk of heart disease?	Narrowing of the arteries means the heart has to work harder to pump blood around the body. It will be deprived of oxygen, cells will die. This is a heart attack.
How can the misuse of drugs increase the risk of a heart attack?	Ecstasy, cannabis, nicotine, and alcohol can increase blood pressure and heart rate.
What is homeostasis?	Keeping conditions inside the body the same through the use of nervous and hormonal communication systems.
What is the function of automatic control systems in the body?	They maintain a range of factors at steady levels and this is required for cells to function properly. Factors include: Water levels, salts levels, nutrient levels, toxic waste products (eg. Carbon Dioxide and urea).
How do these automatic control systems work?	- Receptor detects the stimuli (change). - Processing centre receives the information and coordinates a response. - Effector produces an automatic response.
What is a negative feedback system?	A system where any change results in an action that reverses the change.
Why is a a balanced water level important?	It maintains the concentration of cell contents at the correct level for cell activity.
How are water levels balanced?	By balancing gains from food, drink and respiration, and losses from sweating, breathing, faeces, and urine excretion.
How do kidneys balance water levels?	They produce dilute or concentrated urine as a response to concentration of blood plasma, which is effected by external temperature, exercise level, and intake of fluids and salt.
What controls the concentration of urine?	ADH, which is released into the blood stream by the pituitary gland.
How is ADH secretion controlled?	- Receptors in the brain detect changes in blood plasma concentration. - If it is too high, it triggers ADH release. When it is too low, no ADH is released. - ADH travels to the kidneys and effects the amount of water that can be reabsorbed back into the blood. The more ADH, the more water is reabsorbed.
What can drinking alcohol lead to?	The production of greater volumes of more dilute urine, due to ADH suppression, which can lead to dehydration and adverse effects on health.
What can taking Ecstasy lead to?	Smaller volume of less dilute urine, due to increased ADH production. Body-fluid build-up can lead to brain damage and death.

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