A1 Required Practicals 1-6 Classes

How do you calculate the rate of reaction, using time, for starch hydrolysis?

Rate of reaction = 1 divided by the time it took for all the starch to be hydrolysed.

What formula is used to dilute an enzyme solution?

C1V1 = C2V2.

How to figure out what volume of a solute to use to dilute a concentration?

Use the formula:

Conc wanted/full conc x total volume

take answer away from total to find water

What is the significance of a control in an enzyme experiment?

It helps to show that the observed effects are due to the enzyme and not other factors.

What is the significance of measuring the volume of oxygen produced in the catalase experiment?

It indicates the rate of reaction of the enzyme catalase with hydrogen peroxide.

What is the purpose of using a water bath in experiments?

To provide a controlled temperature environment for reactions.

What is the uncertainty of a ruler measurement?

±1 mm

to find uncertainty, divide the intervals by two, then divide this by what is being measured

What is the purpose of using hydrochloric acid in the preparation of stained squashes of cells?

To kill cells, macerate the tissue, stop mitosis/reactions

Why is the sample gently squashed during the preparation of stained squashes?

Single, thin layer of cells (spread out) so light passes through

Why is the tip of the root used in root tip squash?

It is an area of growth where some cells are in mitosis. mitosis occurs

How is the length of a cell measured using an eyepiece graticule?

By measuring the length of the cell in graticule divisions and calibrating with a stage micrometer.

How do you calculate the mitotic index?

By using the formula: (Number of cells in mitosis ÷ Total number of cells).

What is the reason for using a stain on root tips?

To highlight chromosomes for better visibility under a microscope.

What is the first step in ensuring a representative sample when examining cells?

Examine a large number (20 or more) of fields of view or many cells.

Also method of ensuring cells only appear in one field of view (top + right), or root tip from same species/age

What is the significance of the x-axis intercept on a calibration curve for percentage change of mass of plant tissue in different sucrose concentrations?

It indicates the water potential of the plant tissue.

What should be controlled to ensure consistent results in the water potential experiment?

Temperature fluctuations, by using a water bath.

What is accuracy?

A measurement result is considered accurate if it is close to the true value.

How can you ensure accurate results when measuring the mass of potato chips?

Make sure the potato chips are dried thoroughly before measuring.

How would you create a dilution series from a 2M glucose solution?

Dilute the 2M solution by mixing it with water to create lower concentrations. The use that dilution to dilute further.

What should be consistent in a column of results?

The same number of decimal places.

How does solvent concentration affect membrane permeability?

Higher solvent concentration disrupts membrane structure, increasing permeability.

What is the effect of temperature on membrane permeability?

At temperatures very low or high the permeability increases. Between 0-45°c, as the temperature increases, so does the permeability.

What happens to membrane permeability below 0°C?

Ice crystals damage the membrane, increasing permeability.

What happens to the phospholipid bilayer above 45°C?

Proteins denature and phospholipids move far apart, increasing permeability.

How can pH affect membrane permeability?

Extreme pH levels can denature intrinsic proteins by breaking the ionic and hydrogen bonds, increasing permeability.

What should be controlled in the beetroot permeability investigation?

Variables such as temperature, time, and beetroot size.

Why is it important to rinse beetroot cubes before placing them in the solution?

To remove pigment released during preparation that has not leaked during the experiment.

How do you use a colorimeter in this experiment?

Calibrate it using distilled water and measure absorbance/transmission of the solutions.

How does detergent affect cell surface membranes?

Detergent dissolves phospholipids and increases membrane permeability.

What is the importance of using beetroot discs of the same dimensions in the permeability experiment?

Using discs with the same dimensions ensures consistent surface area, which affects diffusion rate and absorbance readings.

What are the safety precautions to take when conducting a dissection?

Use sharp instruments, cut away from oneself, wear gloves, disinfect equipment, and ensure safe disposal of specimens.

What are the key components of a biological drawing?

Use single lines, no shading, draw outlines only, maintain scale, and include labels and magnification.

What is done to sterilise equipment in aseptic technique?

Flame equipment and the neck of bottles.

How should agar plates be handled to prevent contamination?

Lift the lid at an angle and work closely to a lit Bunsen burner.

What is measured to evaluate the effectiveness of antimicrobial substances?

The area of zones of inhibition around antimicrobial agents.

How do you calculate percentage error