Active Transport

Question 1

Why is active transport sometimes needed (instead of diffusion) to help maintain the internal environment of a cell?

Answer 1

Because …
Molecules and ions often need to be moved across a membrane against their concentration gradient
Substances must be transported far quicker than diffusion allows

Question 2

What is the process of active transport described as?

Answer 2

Cells can use carrier proteins to PUMP these substances across the membrane in a process called active transport.

Question 3

What does active transport require ?

Answer 3

Active transport requires the expenditure of energy in the form of ATP ADENOSINE TRIPHOSPHATE
ADP is produced by respiration in the mitochondria

Question 4

What does active transport use to act as a pump?

Answer 4

Active transport uses carrier proteins that act as a pump

Question 5

Is each carrier protein the same?

Answer 5

• Each carrier protein is S P E C I F I C for one of a few molecules
• Only those that are complementary will fit

Question 6

How do carrier proteins work?

Answer 6

1. The COMPLEMENTARY molecule binds to the carrier protein
2. ATP also binds to the carrier protein
3. The carrier protein changes shape and the energy from ATP is used to transport the molecule against the concentration gradient
4. As the molecule is released, the carrier protein goes back go its original shape

Question 7

Which an carry molecules at a faster rate diffusion or carrier proteins?

Answer 7

The carrier proteins can carry molecules at a much faster rate than diffusion.

Question 8

What is the proper definition for active transport?

Answer 8

Active transport is the:
 Movement of substances against a concentration gradient 
From a low to high concentration 
Using ATP (energy)
Using a CARRIER protein

Question 9

Why does active transport need to take place in root hair cells?

Answer 9

Root hair cells

- the absorption of mineral ions by root hair cells e.g. Magnesium ions

Question 10

Why does active transport take place in the small intestine?

Answer 10

The absorption of glucose and amino acids by villi in the small intestine

Question 11

What does active transport take place in neurones?

Answer 11

The movement of sodium and potassium ions in a neurone

Question 12

Where does active transport take place in plants?

Answer 12

The loading of sugar from the leaf into the phloem in plants.

Leaf –> Phloem

Question 13

What is bulk transport ?

Answer 13

Bulk transport is moving large amounts of material

Question 14

Note

Answer 14

All mechanisms of movement across membranes we have looked at so far involve individual ions or molecules moving.
Cells can also move substances in bulk.

Question 15

What are many of the substances that enter cells too large to be transport through?

Answer 15

Many of the substances that enter cells are too large to be transported through the bilayer or transport proteins

Question 16

What is endocytosis?

Answer 16

The bulk transfer of materials INTO the cells occurs by endocytosis

Question 17

What is exocytosis?

Answer 17

The bulk transfer of materials OUT of the cell occurs by exocytosis.

Question 18

What happens during endocytosis ?

Answer 18

During endocytosis the plasma membrane invaginates and engulfs the material to be absorbed.

Question 19

What is the name of the process endocytosis when the material being absorbed is of a solid nature?

Answer 19

When the materials being absorbed is of a solid nature the process is known as PHAGOCYTOSIS

Question 20

What is the name of the process endocytosis when the material being absorbed is of liquid form or fine suspension?

Answer 20

When the material being absorbed is in liquid form or fine suspension the process is known as Pinocytosis.

Question 21

What is a phagocytic vacuole ?

Answer 21

A phagocytic vacuole containing the engulfed material is formed

Question 22

What is the process of endocytosis ?

Answer 22

• membrane folding in/engulfing
• membrane fuses with itself/pinches off
• formation of a vesicle
• vesicle moves through CYTOPLASM along the cytoskeleton

Question 23

What is exocytosis ?

Answer 23

Exocytosis is the REVERSE PROCESS of endocytosis and involves the REMOVAL of solid material from a cell
Reverse pinocytosis:
Reverse pinocytosis eliminates materials in solution or fine suspension

Question 24

Give an example of a cell in the body which uses phagocytosis ?

Answer 24

White blood cells can engulf pathogens by phagocytosis

Question 25

What happens once the pathogens have been engulfed by white blood cells?

Answer 25

Once they have engulfed the pathogen, vesicles containing LYSOSOMES are used to digest the enzymes.