Edexcel A-Level Biology Algebra Skills

Practise Edexcel A-Level Biology algebra skills through BMI rearrangement, cardiac index units, enzyme-rate formulae and physiological calculations.

Exam points

rearrange BMI or cardiac-output formulae before substituting biological measurements
calculate cardiac index, heart rate or MAP while preserving compound units
substitute graph-read Vmax and K values into enzyme-rate formulae accurately

Covered syllabus points

A.2.1—Mathematical symbols A.2.2—Changing the subject of an equation A.2.3—Substitution into algebraic equations A.2.4—Solving algebraic equations A.2.5—Logarithmic quantities

[Maximum number: 3]

The human body responds to changes in both its internal and external environments.

The heart responds to adrenaline by increasing cardiac output.

Cardiac output = heart rate × stroke volume

The formula shows how to calculate the cardiac index. This is a method of adjusting cardiac output values for the body surface area of an individual.

\text { cardiac index }=\frac{\text { cardiac output in } \mathrm{dm}^{3} \mathrm{~min}^{-1}}{\text { body surface area in } \mathrm{m}^{2}}

The table shows some information for cardiac output, body surface area and cardiac index for two individuals.

Table for Question A.2 Algebra question 1 — Edexcel A-Level Biology A2

Complete the table to show the units for cardiac index, the cardiac index for individual A and the cardiac output for individual B .

A calculation showing the following steps:

- calculation of cardiac output (1)

- correct unit stated (1)

- calculation of cardiac index (1)

mp 1 for $(1.49 \times 2.8)=4.2$ /4.17 / 4.172

mp 2 for $\mathrm{dm}^{3} \mathrm{~min}^{-1} \mathrm{~m}^{-2}$ ACCEPT $\mathrm{dm}^{3} \mathrm{~m}^{-2} \mathrm{~min}^{-1}$ ACCEPT $\mathrm{dm}^{3}$ per min per $\mathrm{m}^{2}$

Mp3 for (6.9/1.92) =3.5 / 3.49 / 3.489

ACCEPT values / units in working if table is empty (or by formula)

(3)

[Maximum number: 3]

Many people swim as part of their regular exercise.

Regular swimming affects resting heart rate and cardiac output.

\text { cardiac output }=\text { stroke volume × heart rate }

The table shows the mean resting cardiac output and mean resting stroke volume for a group of regular swimmers and a control group.

Table for Question A.2 Algebra question 2 — Edexcel A-Level Biology A2

Using the data in the table, calculate the difference in resting heart rate between these two groups.

Give your answer to 2 decimal places with appropriate units.

An answer showing the following steps:

- calculation of heart rates (1)

- calculation of change in heart rate (1)

- correct number of decimal places and units (1)

ECF for mp1 correct calculation in $\mathrm{cm}^{3}$
Example of calculation:
$4.43 \div 0.0744=59.543$ $4.21 \div 0.0584=72.089$
72.1-59.5=12.546
ECF mp2 subtraction ( from mp1) and
correct number of d.p
Answer= $12.55(\mathrm{~b}) \mathrm{pm}$
Correct answer with units - 3 marks

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Covered syllabus points

A.2 Algebra question 1

A.2 Algebra question 2