A secondary active transporter useto move another molecule Selected Answer: an i

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A secondary active transporter useto move another molecule Selected Answer: an ion's concentration gradient : against it's concentration gradient Answers: ATP directly: out of a cell ATP directly down it's concentration gradient ATP directly against it's concentration gradient an ion's concentration gradient: into a cell an ion's concentration gradient: against it's concentration gradient two of the above are correct Question 2 Aln) gated channel is opened or closed by a Selected Answer: mechanically : stretching the cells membrane Answers chemically: ligand binding to a receptor chemically: stretching the cells membrane mechanically: ligand binding to a receptor mechanically: stretching the cells membrane A & D B & C Question 3 For a cell with NO channels open, the act of opening a Na channel will cause Na to rapidly diffusethe cell Selected Answer two of the above are correct Answers into : depolarize into : hyperpolarize out of : depolarize out of: hyperpolarize Question 4 For a cell at-70 mV a stimulus that closes a few Na channels would decrease the race of Na diffusion Selected Answer: out of : depolarize Answers a cel causing the cell so into : depolarize into :hyperpolarize out of: depolarize out of: hyperpolarize

Explanation / Answer

1.  an ion's concentration gradient ; into a cell

A secondary active transporter uses the energy which is derived from the energy that has been stored n the form of ionic concentration differences between the two sides of the cell membrane. It does not derive energy from ATP molecules [ contrary to primary active transport ].

2. chemically; ligand binding to a receptor

Ligands are chemical messengers such as a neurotransmitter, which opens to allow ions such as Na+, K+, Cl-- etc to pass through the membrane.

3. into; depolarize

A stimulus first causes Na+ channels to open which results in n Na+ ions to rush into the cell and since Na ions are positively charged, and the membrane depolarises.

4. into; hyperpolarize

If the influx of Na+ ion decreases, the inside of the cell membrane depolarises. Hyperpolarisation of cells occurs if there is an increase of negative charge on the inside of the cell membrane.

5. increase; depolarize

An influx of positive ions into a cell will depolarize the cell because the inner side of the cell membrane will become positively charged.

6. depolarize, inward movement of Na+

As the sodium ions move inside a cell, depolarization occurs as the positive charge increases on the inner side.

7. inward

Anions are negatively charged ions so if the diffusion gradient is positive, the movement is inwards.

8. not change the membrane potential

Because normally the inside of the cell has a low concentration of Na+ ions and the outside has a higher concentration so increasing the Na+ ion concentration will not change the membrane potential.

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