Biology Remove Summer Exam

Enzyme Diagram

What is the role of enzymes?

Biological catalysts in metabolic reactions.

They increase the rate of reaction.

How does temperature affect enzymes?

At low temperatures enzymes will work slowly as there is not enough energy.

At very high temperatures, the enzymes will become denature as the active sites become deformed.

PRACTICAL: How enzyme activity can be affected by changes in temperature:

• Change the temperature (20,30,40,50,60 degrees C)

• Use the protease enzyme, trypsin and the protein milk powder, marvel.

• Measure the time taken for marvel to turn colourless.

• Do this by drawing an X on the bottom of the beaker and stop the time when you can see the X.

• Measure the time in minutes and seconds using a stopwatch.

• Keep the enzyme and substrate concentrations the same by measuring them.

• Repeat five times and take an average.

How does pH affect enzymes?

At high and low pHs enzymes also become denatured as the active sites become deformed. Most enzymes work best at a pH of 7.

PRACTICAL: How enzyme activity can be affected by changes in pH

• Change the pH level (3, 5, 7, 9).

• Use the protease enzyme, trypsin and the protein milk powder, marvel.

• Measure the time taken for marvel to turn colourless.

• Do this by drawing an X on the bottom of the beaker and stop the time when you can see the X.

• Measure the time in minutes and seconds using a stopwatch.

• Keep the enzyme and substrate concentrations the same by measuring them.

• Repeat five times and take an average.

Diffusion

The movement of particles from an area of high concentration to an area of lower concentration.

What factors affect the rate of diffusion?

Surface area to volume ratio, distance, temperature and concentration gradient.

What is the concentration gradient?

The difference in concentration of two areas.

The steeper the concentration gradient…

the faster the rate of diffusion.

PRACTICAL: Diffusion non-living system

Place a potassium permanganate crystal (purple) into water and observe the colour diffusing throughout the water.

PRACTICAL: Diffusion living system

• Beetroot cells contain a purple pigment.

• Place four cubes of beetroot in four test tubes filled with water and heat each test tube at a different temperature.

• The higher the temperature, the faster the rate of diffusion.

What is respiration?

The release of energy (ATP) from glucose that takes place inside all living cells.

Aerobic respiration word equation:

Glucose + oxygen → carbon dioxide + water + energy (ATP)

Aerobic respiration symbol equation:

C₆H₁₂O₆ + 6CO₂ + 6H₂O + 36ATP

Anaerobic respiration word equation:

glucose → lactic acid + energy

Differences between aerobic and anaerobic respiration:

• Aerobic respiration uses oxygen and anaerobic does not.

• Aerobic respiration produces more energy.

• Aerobic respiration takes place in the mitochondria of a cell and anaerobic respiration takes place in the cytoplasm.

PRACTICAL: Investigate the evolution of carbon dioxide from respiring seeds

• Place germinating seeds in one test tube and boiled seeds in another.

• Suspend hydrogen carbonate indicator above the seeds using gauze.

• Seal with a bung and leave for 1–2 days.

• Observe the color change in the indicator.

PRACTICAL: Investigate the evolution of heat from respiring seeds

• Place germinating seeds in one flask and boiled seeds in another.

• Insert a thermometer into each flask.

• Seal loosely with cotton wool.

• Record temperature over several hours.

• Repeat and take an average

Thorax structure

Role of diaphragm and intercostal muscles in ventilation

• The diaphragm contracts and moves downwards.

• The intercostal muscles contract and move the ribs upwards and outwards.

• This increases the size of the chest and decreases the air pressure inside it which sucks air into the lungs.

How are alveoli adapted for gas exchange?

-Large surface area to volume ratio

-Lots of alveoli

-Walls of alveoli are thin (short diffusion distance)

-Good blood supply to maintain steep concentration gradient

What are the biological consequences of smoking in terms of cilia?

Cilia are small hairs in the trachea. They waft mucus up to the throat to be swallowed. The tar in cigarettes stops this process. Chest infections become more likely.

What are the biological consequences of smoking in terms of alveoli?

The walls inside the alveoli can become damaged, reducing the surface area for gas exchange. This could lead to emphysema.

What are the biological consequences of smoking in terms of the circulatory system?

The walls of arteries can be damaged by chemicals in the tar. This leads to a greater chance of blood clots forming and can lead to coronary heart disease.

Effect of exercise on breathing practical

• Make on person run 1km and 1 person stand still.

• After, measure the rise and fall of their chest (breaths) for 1 minute.

• Repeat this and take an average.

PRACTICAL: Investigate the release of carbon dioxide in humans

• Set up a boiling tube with limewater or hydrogen carbonate indicator.

• Insert a delivery tube with a mouthpiece into the tube, ensuring the exhaled air bubbles through the solution.

• Inhale normally, then exhale slowly through the mouthpiece into the solution.

• Observe the change in the indicator:

  • Limewater: Turns cloudy/milky if CO₂ is present.

  • Hydrogen carbonate indicator: Changes from red to yellow if CO₂ is present.

• Compare results with a control tube containing the indicator or limewater not breathed into.

• Repeat and take an average

Why do simple unicellular organisms rely on diffusion for movement of substances in and out of the cell?

• They have a large surface area to volume ratio

• Short diffusion distance

• No need for a transport system

Why do multicellular organism need a transport system?

• They have a small surface area to volume ratio

• Large diffusion distance

• More efficient

Blood is made up of:

Red blood cells, white blood cells, platelets and plasma

Role of plasma:

Transports carbon dioxide, digested food, urea, hormones and heat energy

Adaptations of red blood cells to transport oxygen:

-No nucleus makes more space for hemoglobin

-Biconcave disc shape causes a large surface area for fast diffusion

-Carries hemoglobin (binds to oxygen efficiently

How does the immune system react to disease?

By using white blood cells.

Roles of white blood cells:

-Produces antibodies to destroy microorganisms.

-Prevents disease by engulfing pathogens

Phagocytes

Engulf bacteria (pathogens)

Lymphocytes

Produce antibodies to destroy pathogens.

What does vaccination result in?

The manufacturing of memory cells (specialised blood cells that remember specific antigens) which enables future antibody protection to the pathogen to occur sooner, faster and in greater quantity.

How do platelets prevent blood loss?

They form clots which prevent blood loss and the entry of micro-organisms

Heart structure

How does the heart function?

The heart is a muscular pump. The right-hand side of the heart is responsible for pumping deoxygenated blood to the lungs. The left-hand side pumps oxygenated blood around the body.

How does heart rate change during exercise (adrenaline)?

-Muscles respire more (more energy)

-More oxygen used and more carbon dioxide produced

-Heart needs to deliver more oxygen to cells to meet demand

-High acidity in blood due to carbon dioxide

-Brain sends signal to pacemaker (increases heart rate)

Factors that increase the risk of coronary heart disease (disease leading to heart attacks):

• Poor diet

• Stress

• Smoking

• Lack of exercise

Artery and vein structure

Arteries carry blood under high pressure and veins carry blood under low pressure.

Capillary structure

One cell thick to allow for the exchange of materials.

Circulatory system structure