Top answers

Guard cells open and close stoma in different conditions. When light intensity is high, potassium ions move into guard cells. Describe how this movement of potassium ions causes the stoma to open.

When the potassium ions move into the guard cells they increase the concentration. This causes water to move into the guard cells from more dilute areas by osmosis. The additional water leads to the guard ce...
EW
Answered by Emily W. • Biology tutor
34180 Views

P is a point on a circle with the equation x^2 + y^2 = 45. P has x-coordinate 3 and is above the x axis. Work out the equation of the tangent to the circle at point P.

First insert x = 3 into the equation of the circle3^2 + y^2 = 459 + y^2 = 45 take 9 away from both sidesy^2 = 36 take the square root of both sidesy = 6 (not -6 as P is above the x-axis)Next find the gradien...
EW
Answered by Emily W. • Maths tutor
3962 Views

Calculate the pH of a 0.0131 mol dm^-3 solution of calcium hydroxide at 10 degrees centigrade.

Multiply by 2 because calcium hydroxide = Ca(OH)2 so 2 x [OH-] per molecule.[OH-] = 0.0131 x 2 = 0.0262 Insert [OH-] value into the equilibrium equation along with the value of Kw at 10 degrees centigrade 2....
EW
Answered by Emily W. • Chemistry tutor
9244 Views

Explain why adding small amounts of acid or base hardly changes the pH of an acidic buffer solution.

An acidic buffer solution is made up of a weak acid (e.g. ethanoic acid) and a salt containing its conjugate base (e.g. sodium ethanoate). It resists pH change via two mechanisms: The fact that the acid is w...
Answered by • Chemistry tutor
7860 Views

The genetic code is described as degenerate, universal and overlapping. Explain these terms.

The genetic code is universal because all species use the same four bases A,T,C and G, and each base sequence codes for the same amino acid in all species. despite the 64 possible codons (sequence of three b...
EW
Answered by Emily W. • Biology tutor
54229 Views