2A- Exchange of substances

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Why is having a large surface area to volume ratio good?

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1

Why is having a large surface area to volume ratio good?

Organisms that have a small surface area to v ratio require a further distance for gases to move and require a specialised system in order to provide adequate gas exchange

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2

Name 3 features of an effective gas exchange surfaces

  1. Large surface area (folded membranes in mitochondria)

  2. Thin walls (capillary walls)

  3. Steep concentration gradient (a good blood supply provides a constant flow of oxygen)

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3

What is ficks law

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4

What is the structure of a cell membrane?

  • Phospholipid bilayer

  • Glycoproteins and glycolipids

  • Channel and carrier proteins

  • Cholesterol

<ul><li><p>Phospholipid bilayer</p></li><li><p>Glycoproteins and glycolipids</p></li><li><p>Channel and carrier proteins</p></li><li><p>Cholesterol</p></li></ul>
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5

What is meant by the fluid mosaic model?

Fluid: the phospholipids can easily move around and embed new proteins

Mosaic: the random association of proteins within the membrane

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6

Describe freeze-fracture

Freezing the cell membrane and then breaking it apart →fracturing it down the middle → results show smooth mosaic on inside.

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7

Describe plant protein

Lectins are labelled with ferritin (visible under electron microscope) → showed membranes are asymmetrical

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8

Describe mouse cells

  • Fusing mouse cells with human cells, specific membranes were labelled

  • 1 min after - protein in the same position

  • 40 min - complete intermixing

  • showed proteins diffuse through membranes and proved they’re fluid

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9

What is facilitated diffusion

The movement of polar, particles from a high to lower concentration through a channel or carrier protein

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10

Define active transport

The movement of particles from low to higher concentration which requires energy in the form of ATP, also requires a carrier protein.

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11

What is endo/exocytosis?

Endocytosis: Cell membrane forms a vesicle and engulfs the molecule (proteins + lipids etc)

Exocytosis: Vesicle fuses with the cell membrane releasing the molecules (Enzymes + hormones)

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