Past Paper Mistakes Flashcards by Ibrahim Ayyubi

Give two advantages of using an electron microscope over a light microscope.

Higher Resolution
Higher Magnification

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What type of pathogen causes malaria?

Protist

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Describe 4 parts of the body which prevents pathogens from entering.

Skin
Stomach
Eyes
Breathing System

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How does the skin prevent pathogens from entering?

Skin acts as a barrier
Oil on the skin
Repels pathogens
Scabs form over cuts making a barrier
Platelets make the are involved in forming the scab.

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How does the stomach prevent pathogens from entering?

Contains HCI
HCI kills bacteria
In food or swallowed mucus

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How do the eyes prevent pathogens from entering?

Produce tears
Contain enzymes which kill bacteria
Tears are antiseptic

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How does the breathing system prevent pathogens from entering?

Trachea/bronchi/nose produce mucus.
Mucus is sticky
Mucus traps bacteria
Mucus carried away by cillia.

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How does the body defend itself from pathogens inside the body?

immune system / white blood cells (WBCs)
WBCs engulf pathogens
antitoxins are produced
(antitoxins) neutralise toxins / poisons (produced by pathogen)
antibodies are produced
(antibodies) help destroy pathogens
memory cells (are formed)
(memory cells give a) more rapid response if pathogen re-enters

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Describe the transport of water through a plant from the roots to the atmosphere.

water is transported in xylem
water evaporates from leaves
through the stomata

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What are the factors that affect water loss in plants?

Amount of Stomata
More leaves
Bigger leaves

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Suggest two reasons why the rate of water loss changes in plants.

Temperature
Light Intensity
Wind (higher wind = more water loss)

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Describe a test that could show that a person’s urine contains glucose.

Benedicts reagent and heat to 90 degrees Celsius.
Turns brick red.

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The body cells of a person with untreated diabetes lose more water than the body cells of a person who does not have diabetes.
Explain how diabetes can cause the body cells to lose more water.

the blood is more concentrated with water but still low concentration.

(so) water moves out of cells by
osmosis

water moves through a partially
permeable membrane

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Describe how the small intestine is adapted for efficient absorption.

projections / folds / villi provide a
large surface area

walls of projections / folds / villi / capillaries are thin / one cell thick for shorter absorption / diffusion distance

(small intestine is) very long, increasing time (for absorption)

good / efficient blood supply to maintain concentration gradient

cells have many mitochondria for (aerobic) respiration for active transport or cells have many mitochondria for energy release for active transport

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Define double circulatory system.

Blood enters the heart
twice for every (one) circuit
around the body

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Explain why having only one ventricle makes the circulatory system less efficient than having two ventricles.

oxygenated and deoxygenated
blood mixes (so) less oxygen reaches the
body / tissues / cells

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Explain why an axolotl may die in water with a low concentration of oxygen.

concentration gradient (of
oxygen) is shallow(er) / less
steep

(therefore) less oxygen diffuses
into blood / cells / gills

less (aerobic) respiration
occurs so less energy is
released / available

(so) less metabolism

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Name the type of cell that divides when a new gill grows.

Stem cells

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Name one condition that could be treated using regenerated human tissue.

paralysis
diabetes
Parkinson’s
heart disease
stroke
cystic fibrosis
cancer
burns

Suggest one reason why an axolotl is a suitable animal for research in the laboratory.

Not dangerous
Easy to breed
Don’t take much space

An axolotl may not be a suitable animal to study when researching regeneration in
human tissue.

Suggest one reason why.

it’s not a mammal or it is an amphibian
regeneration in gills may be different to that in other organs
metabolism / body
processes are too different
to humans

Name 3 places carbohydrase is produced?

Salivary Gland
Small Intestine

One symptom of pancreatic cancer is weight loss.
Explain how pancreatic cancer may cause a person to lose weight

reduced/no enzyme production released (from pancreas)

so food is not broken down fully

less glucose available for respiration

so more (body/
stored) fat used up in
metabolism / respiration

A monoclonal antibody has been produced to treat pancreatic cancer.

Explain how the monoclonal antibody works to treat pancreatic cancer.

monoclonal antibody is attached to radioactive substance / toxin /
drug / chemical

monoclonal antibody will (only) attach to / target (antigen on)
cancer cells / tumour

(so) radioactive substance / toxin / drug / chemical will (bind to cancer cells and) stop them
growing / dividing

Two symptoms of infection by Salmonella are vomiting and diarrhoea. What causes these symptoms?

Toxins from bacteria

Which two blood vessels carry deoxygenated blood?

Pulmonary Artery Vena Cava

Compare the structure of an artery with a structure of a vein.

Artery's have a thicker layer of muscle. Veins have a wider lumen. Veins have valves and arteries don't.

What condition may be treated with an artificial pacemaker?

Irregular heartbeat

Explain how a magnesium deficiency causes yellow leaves.

Magnesium is required for chlorophyll. Chlorophyll is the green pigment which is needed for photosynthesis. Without photosynthesis glucose cannot be produced. So the plant converts less glucose into protein for growth, so growth is stunted.

How are monoclonal antibodies produced?

Inject a mouse with a dead or inactive pathogen. The mouse creates lymphocytes with complimentary antibodies. Fuse with a cancer cell to create a hybridoma. It then divides. Purify and collect monoclonal antibodies.

Describe how a student could test cow's milk to show whether it contains protein and different types of carbohydrates.

Biuret reagent (allow CuSO4 and NaOH) tests for protein * add Biuret reagent to milk * solution will turn (from blue) to lilac if positive * iodine solution tests for starch (ignore iodine unqualified) * add iodine solution to milk * solution will turn (from orange / brown) to blue / black if positive * Benedict’s reagent tests for sugars * add Benedict’s reagent to milk and boil / heat (allow any temperature above 60 °C) * solution will turn (from blue) to (brick) red / brown / orange / yellow / green if positive

What is the function of the focus knob?

Improve resolution

Describe two aseptic techniques the student should have used in the agar jelly practical?

Sterilise Equipment Secure lid of petri dish with adhesive tape.

Explain why a death of a pond snail can cause the concentration of CO2 to increase.

Snail is being decayed by bacteria which are respiring so they release CO2.

Explain how amylase breaks down starch in the lock and key theory.

starch / substrate binds to active site (of enzyme) (because) shape of active site and substrate are complementary a chemical reaction occurs to produce smaller molecules

Which structure in a leaf mesophyll is not found in a root hair cell?

Chloroplasts

Water is taken in by the roots, transported up the plant and lost from the leaves. Which scientific term describes this movement of water?

Transpiration Stream

Compare the structure and function of xylem tissue and phloem tissue.

Structure Xylem contains lignin and phloem does not (contain lignin) phloem cells have pores in their end walls and xylem cells do not have pores in their end walls xylem is made of dead cells and phloem is made of living cells. Function xylem transports water / mineral ions and phloem transports (dissolved) sugars * xylem is involved in transpiration and phloem is involved in translocation * xylem transports in one direction and phloem transports in both direction.

Describe what happens to cells when a tumour forms.

Cells grow uncontrollably.

Some types of cancer can cause the numbers of blood components in a person’s body to fall to a dangerously low level. A person with one of these types of cancer may experience symptoms such as: * tiredness * frequent infections * bleeding that will not stop after the skin is cut. Explain how a very low number of blood components in the body can cause these symptoms.

Tiredness * fewer red blood cells * so less haemoglobin * so less oxygen transported around the body * so less (aerobic) respiration can take place * so more anaerobic respiration takes place * less energy released for metabolic processes or less energy released so organs cannot function as well * lactic acid produced (during anaerobic respiration) causes muscle fatigue Frequent infections * fewer white blood cells / phagocytes / lymphocytes * so fewer antibodies produced or less phagocytosis * so fewer pathogens / bacteria / viruses killed Bleeding * fewer platelets * so blood does not clot as easily

A person has a tumour blocking the tube leading from the gall bladder to the small intestine. Explain why this person would have difficulty digesting fat.

no / less bile reaches the small intestine (so) less / no emulsification of fat (so) smaller surface area for lipase to break down fat pH of small intestine is not neutralised / alkaline (so) lipase is not at its optimum pH to break down fat

True or False? Releasing saliva when food enters the mouth is a reflex action.

True

True or False? Running away from danger is a reflex action.

False

What stimulus causes the pupil to shrink?

Bright Light

Describe the reflex action.

How would an increase in the concentration of carbon dioxide in the atmosphere cause an increase in air temperature?

Less loss of heat.