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Biology Year 1 > Chapter 4 - Transport Across Cell Membranes > Flashcards

Chapter 4 - Transport Across Cell Membranes Flashcards

1
Q

What is a cell surface membrane

A

A phospholipid bilayer

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2
Q

How are the phospholipids structured in a cell surface membrane

A
  • Hydrophilic heads outwards, hydrophobic tails inwards
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3
Q

What is meant by the fluid mosaic model

A

Because phospholipids are able to slide over each other, the membrane is flexible and so can constantly change shape

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4
Q

What molecules can diffuse through a cell surface membrane and why

A

Small, non-polar molecules, as these are lipid soluble

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5
Q

Water can’t diffuse through a cell surface membrane, what does this stop from leaving and entering cells

A

Water soluble substance

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6
Q

What does water move through to enter cells

A

Aquaporins / water channels

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7
Q

What are the 2 types of transport protein

A

Protein channels

Carrier proteins

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8
Q

What do protein channels do

A

They form water-filled tubes to allow water-solubles ions to diffuse across the membrane

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9
Q

What do carrier proteins do

A

Bind to ions or molecules (eg glucose and amino acids), then change shape in order to move the molecules across the membrane

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10
Q

What type of transport occurs in carrier proteins

A

Active transport

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11
Q

What other uses do proteins have in a cell surface membrane

A
  • Provide structural support
  • Form cell surface resettles to identify cells
  • Help cells adhere together
  • Act as receptors eg for hormones
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12
Q

What is the function of cholesterol in cell surface membranes and how do they do this

A

Reduce lateral movement of other molecules by binding to hydrophobic tails, making it less flexible and more rigid

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13
Q

How does cholesterol helps animals cells especially

A

Provide strength and support, as animals don’t have cell walls

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14
Q

Why does cholesterol prevent loss of water

A

It is hydrophobic

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15
Q

What are glycolipids made up of

A

Carbohydrates covalently bonded with a lipid

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16
Q

What do glycoplipids do in a cell surface membrane

A
  • Act as recognition sites (cell-surface receptors)
  • Help cells attach to each other to form tissue
  • Help maintain stability of a membrane
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17
Q

What are glycoproteins

A

Carbohydrate chains attached to extrinsic proteins on outer surface of the cell membrane

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18
Q

What functions do glycoproteins do

A
  • Act as recognition sites
  • Help cells attach to each other to form tissues
  • Allow cells to recognise each other (eg lymphocytes recognise own cells)
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19
Q

What is diffusion

A

The net movement of molecules from high to low concentration, until evenly distributed

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20
Q

What is diffusion an example of

A

Passive transport

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21
Q

What is meant by passive transport

A

No external source of energy is used, such as ATP

22
Q

What should be considered when thinking about diffusion

A

Fick’s law

23
Q

What are the three parts to fick’s law

A

Concentration gradient
Diffusion distance
Surface area of membrane

24
Q

What do the parts of fick’s law effect

A

The rate of diffusion

25
Q

What is facilitated diffusion

A

Movement of molecules across the cell membrane vie specific transmembrane proteins

26
Q

What is facilitated diffusion an example of

A

Passive transport

27
Q

What are transmembrane proteins

A

Protein channels

Carrier proteins

28
Q

Explain how protein channels work

A
  • Water filled hydrophilic channels
  • Allow water soluble, small, charged ions to pass across membrane
  • Have to be charged as otherwise can just diffuse across
29
Q

What do carrier proteins do

A

Carry large molecules across cell surface membrane

30
Q

How do carrier proteins work

A
  • Bind with protein

- Change shape so that molecule is released on the inside of the membrane

31
Q

What concentration gradient does facilitated diffusion occur at

A

High to low

32
Q

What is meant by transmembrane proteins being specific

A

Each molecule has its own transport protein

33
Q

What can transmembrane proteins also be used for

A

Active transport with ATP

34
Q

What is osmosis

A

Movement of water molecules from a high water potential to a low water potential across a partially permeable membrane

35
Q

What is osmosis an example of

A

Passive transport

36
Q

What is meant be a selectively/partially permeable membrane

A

A membrane that is permeable to water molecules and a few other small molecules, but not larger molecules

37
Q

What is meant by hypotonic

A

A solution with a high water potential

38
Q

What is meant by hypertonic

A

Solution with a low water potential

39
Q

What is meant by isotonic

A

A solution with the same water potential as the cell

40
Q

What value does the water potential of a solution always have

A

A negative value

41
Q

What kind of value will a high water potential have

A

A less negative one

42
Q

What kind of value will a low water potential have

A

A more negative one

43
Q

What value of water potential will pure water have

A

0

44
Q

What can water potential cause to happen with animal cells

A

Animal cells can shrink or burst as they have no cell wall

45
Q

What is active transport

A

Movement of molecules or ions across cell surface membranes from low concentration to a high concentration using ATP energy and carrier proteins

46
Q

How does active transport work

A
  • Molecule binds to receptor sites in carrier protein
  • On inside of the cell, ATP bonds to the carrier protein, causing it to break down into ADP + Pi
  • Protein Changes shape and opens on the other side of the membrane
  • Molecule is released inside
47
Q

How does co-transport work

A
  • 2 molecules move at once, via carrier protein
  • One moves with the concentration gradient, one moves against it
  • The molecule against the gradient uses energy from the molecule using facilitated diffusion
48
Q

What is an example of co-transport in the human body

A

Absolution of glucose in the ileum

49
Q

Where does the absorption of glucose take place

A

For diagram: Ileum at the top, epithelial cell middle, blood capillary at the bottom

50
Q

What is the ileum

A

Part of the small intestine

52
Q

Explain how glucose is absorbed into the blood

A
  • Sodium moves out of epithelial cell into blood, through sodium-potassium pump via active transport, so there is a low concentration of sodium in the epithelial cell
  • Sodium moves with the concentration gradient from ileum into epithelial cell, co-transport occurs for glucose to also enter
  • Glucose is absorbed into blood through facilitated diffusion, via a carrier protein
53
Q

What is the epithelial cell

A

The outer cell of the small intestine

Biology Year 1 (10 decks)

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