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Biology

A Level

What are the light-dependent reactions of photosynthesis?

In the light-dependent reactions, a photon of light hits an electron located in the thylakoid membrane of the chloroplast in photosystem II. This causes the electron to gain energy and jump to a higher en...

Answered by Sarah C. • Biology tutor

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Briefly describe the mechanism of muscle contraction.

In muscle, myosin protein has 'heads' that act as cross-bridges as they bind to actin, another protein. When ATP binds to myosin, its head detaches from actin, swings forward and rebinds. Rebinding releas...

Answered by Hester G. • Biology tutor

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Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar. Use your knowledge of water potential to suggest how putting honey on a cut kills bacteria. (AQA BIOL1)

Sugar is a solute and is able to dissolve in water. When sugar is dissolved in water, it has a low water potential. Water moves from a high water potential to a low water potential; from where there is a ...

Answered by Charlotte S. • Biology tutor

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What is the Difference between saturated and unsaturated fatty acids?

Firstly, saturated fatty acids are where all the carbon atoms have single bonds between them making the lipid saturated as no more hydrogens can be added. Having

Answered by Katie D. • Biology tutor

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Describe the path of electrical activity through the heart, starting at the sino-atrial node.

The electrical activity is initiated by the pacemaker of the heart, the sino-atrial node at the top of the left atrium. This spreads across the atria before reaching the atrio-ventricular node. Here there...

Answered by Marcus B. • Biology tutor

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