Organelles
What is the function of the nucleus in a cell?
The nucleus controls the cell’s activities and contains genetic material (DNA).
What is the main function of the respiratory system?
To take in oxygen and remove carbon dioxide from the body.
What does the term “surface area to volume ratio” mean?
It is the relationship between the amount of surface area an object has compared to its volume.
What is diffusion?
Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
A student places food colouring into two beakers of water. In the beaker at 30°C, the colour spreads throughout the water in 40 seconds. In the beaker at 10°C, the colour takes 120 seconds to spread. Explain what the data shows about diffusion.
Diffusion occurs faster at higher temperatures because particles have more kinetic energy and move more quickly.
Which organelle is responsible for producing energy in the cell?
The mitochondria.
What is the main function of the heart in the circulatory system?
To pump blood around the body, delivering oxygen and nutrients to cells.
Why do smaller cells usually have a larger surface area to volume ratio than larger cells?
Smaller cells have more surface area compared to their volume, allowing substances to move in and out more efficiently.
What is osmosis?
Osmosis is the movement of water across a partially permeable membrane from an area of high water concentration to low water concentration.
An experiment showed that an enzyme worked slowly at 10°C, fastest at 30°C, and very slowly again at 60°C. Explain why the enzyme activity decreased at 60°C.
The high temperature denatured the enzyme, changing the shape of its active site so the substrate could no longer bind properly.
Explain the role of ribosomes in the cell.
Ribosomes are responsible for protein synthesis; they assemble amino acids into proteins.
Where does gas exchange occur in the lungs?
In the alveoli, where oxygen diffuses into the blood and carbon dioxide diffuses out.
How does a large surface area to volume ratio help cells survive?
It allows nutrients, oxygen, and waste products to move in and out of the cell more quickly.
Explain the difference between passive transport and active transport.
Passive transport does not require energy and moves substances from high to low concentration, while active transport requires energy to move substances from low to high concentration.
Scientists observed that root cells absorbed large amounts of mineral ions when oxygen levels were high, but mineral ion uptake decreased when oxygen levels were low. Explain why this occurred.
Active transport requires energy from respiration. Lower oxygen levels reduce respiration, meaning less energy is available for active transport.
A student observes that a plant cell is able to make food using sunlight. Which organelle is responsible for this process, and how does it work?
The chloroplast. It contains chlorophyll, which captures sunlight and uses it to carry out photosynthesis, producing glucose for energy.
Explain how the circulatory and respiratory systems work together.
The respiratory system brings oxygen into the lungs, where it enters the blood. The circulatory system then transports this oxygen to cells and carries carbon dioxide back to the lungs to be exhaled.
Explain why elephants have large ears in terms of surface area to volume ratio.
Large ears increase surface area, helping elephants lose heat more effectively and regulate body temperature.
Why is facilitated diffusion needed for some substances to enter or leave a cell?
Some molecules are too large or charged to pass directly through the cell membrane, so transport proteins help them move across without using energy.
In an experiment, an enzyme-controlled reaction is carried out at pH 7 and then repeated at pH 3. The reaction rate drops significantly at pH 3. Explain why this happens and predict how enzyme structure is affected.
The change in pH alters the enzyme’s structure by affecting bonds that maintain its shape. At pH 3, the enzyme becomes denatured or its active site changes shape, so fewer enzyme-substrate complexes form, reducing the reaction rate.
A cell has a mutation that prevents ribosomes from functioning properly. Predict what impact this would have on the cell.
The cell would be unable to produce proteins effectively, leading to failure in enzyme production, structural repair, and overall cell function, likely resulting in cell death.
A student is running a 1500m race and begins to feel out of breath and fatigued in the final lap. Explain what is happening in their respiratory and circulatory systems and why this is occurring.
Use arrow format to respond
The muscles require more oxygen than the body can supply. Breathing rate increases to take in more oxygen, and heart rate increases to deliver oxygen faster. When oxygen supply is insufficient, anaerobic respiration occurs, producing lactic acid which contributes to fatigue and breathlessness.
A cube-shaped cell has sides measuring 2 cm. Calculate its surface area to volume ratio.
Surface Area=6a2 Volume=a3
Surface Area = 6×22=24 cm
Volume = 23=8 cm
Surface Area : Volume Ratio = 24:8
Simplified Ratio = 3:1
A plant cell is placed in salty water and begins to lose water rapidly. Explain which transport process is occurring and predict what will happen to the cell.
Osmosis is occurring. Water moves out of the cell into the salty solution because there is a lower water concentration outside the cell. The cell membrane pulls away from the cell wall, causing the cell to become hypertonic.
A student places a dye crystal into a beaker of water. Over time, the dye spreads evenly throughout the water without stirring.
The dye particles move by diffusion from an area of high concentration (near the crystal) to an area of low concentration in the surrounding water. This continues until the particles are evenly distributed and there is no concentration gradient.