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B1.6B1. Characteristics of Living Organisms and Cells

Active transport Core — Combined Science 0653 - Biology Revision Notes & Topical Questions

5 min read 9 parts Lesson 7 of 14 1 quiz

📚 Combined Science 0653 - Biology Hub / Topical Revision
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Lesson summary

B1.6 Active transport — COMBINED SCIENCE notes: Define active transport and describe why it needs energy and where it happens.Active transport = the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy…

  • Against the gradient
  • Small intestine
  • Kidney tubules
  • Root hair cells
  • Carrier proteins
  • Vital process

Part 1 of 7What active transport is

  • Active transport the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.

Part 2 of 7Why energy is needed

Against the gradient
  • Against the gradient the particles move in the opposite direction from the one in which diffusion would move them.
Source
  • Source the energy comes from respiration, so active transport slows or stops if respiration stops.
  • Cells that do a lot of active transport have many mitochondria.

Part 3 of 7Where active transport happens

Small intestine
  • Small intestine epithelial cells of the villi take up glucose.
Kidney tubules
  • Kidney tubules glucose is reabsorbed into the blood in the nephron.
Root hair cells
  • Root hair cells they take up mineral ions from the soil water.

Part 4 of 7Carrier proteins

  • Carrier proteins
    • proteins in the cell membrane that pick up specific molecules and take them across against their concentration gradient.
    • No details of the phospholipid bilayer are needed.

Part 5 of 7Steps in active transport

1
The substance combines with a carrier protein in the cell membrane.
2
The carrier uses energy from respiration to change shape.
3
The change in shape moves the substance across the membrane.
4
The substance is released into the cell.

Part 6 of 7Importance

  • Vital process
    • it moves molecules and ions across membranes when diffusion alone could not.
    • It allows a cell to build up a higher concentration than outside.

Part 7 of 7More from the specification

More from the specification
Movement Against Concentration Gradients
  • Active transport pumps ions or molecules across biological membranes from regions of lower concentration to regions of higher concentration, requiring ATP hydrolysis derived from cellular respiration.
Role of Transmembrane Carrier Proteins
  • Specific membrane carrier proteins bind target solutes on one face of the phospholipid bilayer, undergoing conformational shape changes powered by phosphorylation to translocate the solute across.
Physiological Importance in Plant Root Hair Cells
  • Active transport enables terrestrial root hair cells to absorb dilute essential mineral nutrients from soil water where ambient mineral concentrations are substantially lower than inside the root cytoplasm.
    • (nitrates, potassium, phosphates)
Solvent
  • Liquid in which a solute dissolves.
Solute
  • Substance that dissolves in a solvent.
Water potential
  • A measure of the tendency of water to move, highest in dilute solutions.
Carbon dioxide
  • Gas that turns limewater cloudy.
Dialysis tubing
  • A non-living partially permeable membrane.
Osmosis
  • The diffusion of water through a partially permeable membrane from dilute to concentrated solution.
Tissue
  • A group of similar cells working together to do one job.
Organism
  • A whole living thing made of organ systems.

Key terms

TermMeaning
Active transportMovement of particles against a concentration gradient using energy from respiration.
Carrier proteinA protein in the membrane that carries particles across.
RespirationThe reactions that release energy from food.
Root hair cellA plant cell that takes in water and ions from the soil.
MitochondrionThe organelle that releases energy in respiration.
VilliFolds of the small intestine that absorb food.

Avoid these mistakes

1
Saying active transport follows the concentration gradient — it goes against it.
2
Saying active transport needs no energy — it needs energy from respiration.
3
Forgetting carrier proteins — they carry the particles across.
4
Saying the energy comes from the carrier protein — it comes from respiration.

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