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Biology Unit 1 > Cellular structure and function (Chapter 3) > Flashcards

Cellular structure and function (Chapter 3) Flashcards

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1
Q

what are organelles in eukaryotic cells?

A

Eukaryotic cells have folded membranes and intracellular compartments called organelles.

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2
Q

how can organelles help molecules?

A

This assists molecules to get to their desired destination.

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3
Q

what do each organelle do?

A
  • is responsible for a specific ‘task’.
  • allow different chemical reactions to occur at the same time in different places without interfering with each other
  • maintain concentration of molecules at levels that ensure reactants will collide with each other at optimal rates
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4
Q

what is the role of the cell membrane?

A
  • The boundary of a cell
  • Determines cell identity
  • Receives external signals
  • Transports materials
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5
Q

where is cell wall vs cell membrane?

A
  • Cell wall is found in plant cell and cell membrane is found in both plant and animal cells.
  • Cell membrane is covered by the cell wall which forms the outermost covering of plant cells
  • Cell wall is completely permeable whereas cell membrane is semi-permeable.
  • Cell wall is made up of cellulose and cell membrane is made up of lipids (fats) and proteins.
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6
Q

what is the size of the cell/plasma membrane?

A

Plasma membranes range from 5 to 10 nm in thickness.

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7
Q

size comparison to plasma membrane?

A

For comparison, human red blood cells, visible via light microscopy, are approximately 8 µm wide, or approximately 1,000 times wider than a plasma membrane. Can only be seen with a electron microscope.

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8
Q

what do lipids include?

A

Fats and oils: important as energy-storing molecules
Phospholipids: important component of cell membranes
Steroids: hormones and vitamins

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9
Q

lipids characteristics?

A
  • Contain little water & insoluble in water (hydrophobic)
  • Form effective barrier between two watery environments
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10
Q

what is the cell membrane made of?

A

phospholipids

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11
Q

what are phospholipids made of?

A
  • 2 hydrophobic fatty acid hydrocarbon tails
  • Hydrophilic phosphate group attached to the glycerol & other small groups to the phosphate
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12
Q

what polarity is the phospholipid head?

A

hydrophilic polar head

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13
Q

what polarity is the phospholipid tail?

A

hydrophobic non polar tail

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14
Q

what is in the structure of the plasma membrane?

A
  • transmembrane protein
  • protein channel
  • glycolipid
  • cholesterol
  • peripheral protein
  • integral proteins
  • carbohydrate hain
  • phospholipid bilayer
  • glycoprotein
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15
Q

what model is the plasma membrane?

A

‘The fluid mosaic model’

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16
Q

how is the plasma membrane a fluid mosaic model?

A

Comprises a phospholipid bilayer into which proteins & glycoproteins protrude
- Lipids are the ‘fluid’ part
- Proteins are the ‘mosaic’ part
- Membrane proteins have a variety of functions
Many proteins are glycoproteins

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17
Q

what do some proteins in the plasma membrane form?

A

Some proteins form channels to assist the movement of materials into & out of cell

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18
Q

what are the two types of proteins

A
  • integral membrane proteins
  • peripheral membrane proteins
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19
Q

what are integral membrane proteins?

A

Integral membrane proteins, also called intrinsic proteins, have one or more segments that are embedded in the phospholipid bilayer.

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20
Q

what are peripheral membrane proteins?

A

Peripheral membrane proteins, or extrinsic proteins, do not interact with the hydrophobic core of the phospholipid bilayer.

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21
Q

what is the importance of the plasma membrane?

A
  • Cells membranes have proteins called receptors that bind to signaling molecules and initiate a physiological response.
  • Recognising ‘self’ and ‘non-self’
  • Crossing the membrane
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22
Q

why is the plasma membrane important for signalling?

A

Because membrane receptors interact with both extracellular signals and molecules within the cell, they can affect cell function without actually entering the cell.

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23
Q

how does the plasma membrane recognise self or non self?

A
  • on outer surface are substances called antigens (glycoproteins – signal receivers)
  • a person’s antigens are unique to that person i.e. like a fingerprint
  • antigens perform an important role in the immune system
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24
Q

how permeable is the plasma membrane?

A

plasma membrane is semi-permeable or selectively permeable, therefore allowing only some dissolved materials to cross it

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25
Q

what does a selectively permeable cell membrane mean?

A

A selectively permeable cell membrane is one that allows certain molecules or ions to pass through it by means of active or passive transport.

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26
Q

what are factors governing substances crossing a membrane?

A
  • Size
  • Degree of polarity
  • Not permeable to charged atoms (ions) and metallic ions
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27
Q

how does size affect permeability?

A
  • Permeable to small molecules
  • O2 (2 atoms), CO2 (3 atoms), ethanol (8 atoms), and H2O (3 atoms) due to its small size are permeable – but moves at a reduced rate
  • Not permeable to larger hydrophilic polar molecules, e.g glucose (24 atoms)
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28
Q

how does degree of polarity affect permeability?

A
  • Permeable to hydrophobic molecules
  • May have receptors to help
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29
Q

what do charged atoms (ions) and metallic ions need to permeate the plasma membrane?

A
  • Need channels
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30
Q

summary of how substances can permeate the plasma membrane?

A
  • Lipid-soluble substances of various sizes, such as alcohol, are able to simply dissolve into the phospholipid bilayer and pass easily through membranes.
  • Tiny molecules, such as water & urea, can pass between the phospholipid molecules.
  • Small uncharged molecules, such as oxygen and carbon dioxide, can also pass through the phospholipid bilayer.
  • Larger water-soluble substances, including amino acids and sugars, pass through channels made from protein molecules.
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31
Q

what can protein channels be?

A

Protein channels may be selective for particular substances, and may require energy for transport to occur.

32
Q

what can permeate through the plasma membrane and examples?

A
  • Gases (CO2, N2, O2)
  • Small uncharged polar molecules (ethanol)
  • water (H2O)
  • urea (CH4 N2 O)
33
Q

what can’t permeate through the plasma membrane and examples?

A
  • Large uncharged polar molecules (glucose)
  • ions (K+, Mg2+, Ca2+, Cl-, HCO3-, HPO42-)
  • Charged polar molecules (Amino acids, ATP, Glucose 6-phosphate)
34
Q

what are the types of membrane transpot?

A
  • passive transport (diffusion and facilitated diffusion)
  • active transport
35
Q

what is passive transport?

A

transport where no energy is required

36
Q

what is active transport?

A

transport where energy is required (ATP)

37
Q

what is simple diffusion?

A

The net movement of a substance from region of a high concentration to a region of low concentration.

38
Q

what type of process is simple diffusion?

A

Simple diffusion is a passive process (no energy required)

39
Q

what does diffusion do with concentration?

A

Diffusion moves solutes toward a concentration equilibrium.

40
Q

what is the simple diffusion of water across a semipermeable membrane?

A

osmosis

41
Q

define osmosis?

A

Osmosis is a special form of diffusion involving the movement of water across a semipermeable membrane

42
Q

does cytoplasm have high or low water concentration?

A

Cytoplasm in cells has a relatively high water percentage (lots of water)

43
Q

what happens if the environment outside the cell has a different percentage of water within the cell?

A

If the environment outside the cell has a different percentage of water, the water will diffuse in and out of the cell until equilibrium is reached and vice versa.

44
Q

what are some key characteristics of osmosis and cells?

A
  • Cells are all surrounded by a plasma membrane.
  • Plasma membrane is fluid.
  • It can change shape
  • Depending on the outside conditions of a cell, the cell may swell or lose volume.
45
Q

what is a hypertonic solution?

A

solute concentration inside the cell is lower

46
Q

what happens when the solution is hypertonic?

A

water is transported out from the cell

47
Q

what is a hypotonic solution?

A

solute concentration inside the cell is higher

48
Q

what happens when the solution is hypotonic?

A

water is transported into the cell

49
Q

what is a isotonic solution?

A

solute concentration inside the cell is equal to the solution outside the cell

50
Q

what happens when the solution is isotonic?

A

amount of water transported into the cell equal to the amount of water transported out from the cell

51
Q

what happens of osmosis in animal cells (red blood cells) when in an hypotonic solution (fresh water)?

A

A red blood cell will swell and undergo hemolysis (burst) when placed in a hypotonic solution.

52
Q

what happens of osmosis in animal cells (red blood cells) when in an hypertonic solution (sea water)?

A

Then placed in a hypertonic solution, a red blood cell will lose water and undergo crenation (shrivel).

53
Q

what happens of osmosis in animal cells (red blood cells) when in an isotonic solution?

A

no change in shape of cell, water moves in and out of the cell at the same rate

54
Q

what happens of osmosis in plant cells when in an isotonic solution?

A

cell becomes flaccid

55
Q

what is a flaccid plant cell?

A

A flaccid plant cell is not swollen and the cell membrane does not press against the cell wall tightly.

56
Q

what happens of osmosis in plant cells when in an hypotonic solution?

A

cell becomes turgid

57
Q

what is a turgid cell?

A

A turgid cell is a cell that has turgor pressure because water has entered.

58
Q

what happens of osmosis in plant cells when in an hypertonic solution?

A

cell becomes plasmolysed

59
Q

what is a plasmolysed cell?

A

A plasmolysed plant cell has lost water which causes cell contents to shrink away from the cell wall
- although the cell membrane maintain some contact with the cell wall

60
Q

what are the two types of facilitated diffusion?

A
  • Channel mediated
  • Carrier mediated
61
Q

what is channel mediated facilitated diffusion?

A
  • can enter through protein channels
  • faster than diffusion
62
Q

what is carrier mediated facilitated diffusion?

A
  • involves a specific carrier molecule assisting entry
  • faster than diffusion
  • carrier changes shape during transport
63
Q

what process is active transport?

A

Endergonic process (requires energy)

64
Q

how does active transport move with/against the concentration gradient?

A

Movement against a concentration gradient

65
Q

what does active transport involve?

A

Involves a carrier protein for each substance actively transported

66
Q

what are the proteins involved in active transport?

A

Proteins involved are generally called ‘pumps’. The proteins need to be coupled to an energy providing reaction (commonly the hydrolysis of ATP or the inward movement of proteins)

67
Q

what is the speed of active transport in relation to other modes of transport?

A

Faster than diffusion

68
Q

what is the importance of active transport?

A
  • Uptake of essential nutrients against a concentration gradient.
  • Allows secretory and waste products to be removed against the concentration gradient.
  • Allows cells to maintain concentrations of ions in a non-equilibrium steady state.
69
Q

what is bulk transport?

A

Bulk transport is a mode of transport of large quantities of materials and food particles across the membrane

70
Q

what are the types of bulk transport?

A
  • Exocytosis
  • Endocytosis
71
Q

what is exocytosis?

A

Type of bulk transport that moves large substances out of the cell

72
Q

what are the steps involved in exocytosis?

A
  1. Vesicular transport - a vesicle containing secretory products is transported to the plasma membrane
  2. Fusion - the membranes of the vesicle and cell fuse
  3. Release - the secretory products are released from the vesicle and out of the cell
73
Q

what is exocytosis used for?

A

This is how hormones are secreted and how nerve cells communicate with each other

74
Q

what is endocytosis?

A

Type of bulk transport that moves large substances into the cell

75
Q

what are the steps involved in endocytosis?

A
  1. Fold - plasma membrane folds inwards to form a cavity that fills with extracellular fluid and the target molecules
  2. Trap - plasma membrane continues folding back on itself until the two ends of the membrane meet and fuse, trapping the target molecules inside the vesicle
  3. Bud - the vesicle pinches off from the membrane and is transported to the appropriate cellular location
76
Q

examples of endocytosis?

A

phagocytosis (solid material) and pinocytosis (liquid or dissolved substances)

Biology Unit 1 (4 decks)

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