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Biology > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

All membranes around cells and organelles have the same basic structure and are known as ….

A

Plasma membranes

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2
Q

What is a cell surface membrane?

A

A form of plasma membrane specific to the outside of cells

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3
Q

What are the functions of phospholipids in the membrane?

A

Allow lipid soluble substances to enter and leave the cell
Prevent water soluble substances entering and leaving the cell
Make the membrane flexible and self sealing

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4
Q

What are phospholipids and how to they form a plasma membrane?

A

Hydrophilic tails point to the outside of the cell and are attracted to water
Hydrophobic tails point to the inside and are repelled by water preventing water soluble substances from entering or leaving

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5
Q

What are the functions of proteins that never fully extend across the bilayer

A

Provide mechanical support or act as cell receptors for molecules such as hormones

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6
Q

What are the 2 types of proteins that span the phospholipid bilayer ?

A

Carrier proteins and protein channels

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7
Q

What is a carrier protein?

A

A protein that binds to ions or molecules like glucose and amino acids and change shapes in order to move molecules across the membrane

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8
Q

What is a protein channel?

A

A water filled tube that allows water soluble ions to diffuse across a membrane

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9
Q

List the functions of proteins in a cell surface membrane

A

Provide structural support
Act as channels for water soluble substances
Allow active transport via carrier proteins
Form cell surface receptors for identifying cells
Help cells stick together

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10
Q

What are the functions of cholesterol in cell surface membranes?

A

Reduce movement of other molecules including phospholipids
Make membranes less fluid at hight temperatures
Prevent loss of water and dissolved ions by being very hydrophobic

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11
Q

Is cholesterol hydrophilic or hydrophobic?

A

Hydrophobic

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12
Q

Describe the functions of glycolipids

A

Act as recognition sites
Help maintain the stability of the membranes
Help cells to attach to on another and form tissues

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13
Q

What is a glycolipid?

A

A carbohydrate covalently bonded with a lipid that spans the membrane.

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14
Q

Which part of a glycolipid is on the outside of the cell membrane?
Why is this significant?

A

Carbohydrate

Acts as a cell surface receptor for specific chemicals

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15
Q

What is a glycoprotein?

A

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

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16
Q

What are the functions of glycoproteins?

A

Acts as recognition sites
Help cells attach to one another
Allow cells to recognise each other

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17
Q

What causes a substance to not be able to pass through the cell surface membrane?

A

Insoluble in lipid so cant pass through phospholipids
Too large for channels in the membrane
Has the same charge as the protein channels and therefore are repelled
Electronically charger so cannot pass through non polar hydrophobic tails

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18
Q

What are the functions of membranes in cells?

A

Control the entry and exit of materials
Separate organelles from cytoplasm so that specific metabolic reactions can take place
Provide internal structure systems
Isolate enzymes that might damage the cells
Provide surfaces on which a reaction can occur

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19
Q

Define diffusion

A

The net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower until evenly distributed

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20
Q

Define facilitated diffusion

A

The movement of molecules that cannot normally pass through the membrane from an area of high concentration to low concentration that is facilitated by transmembrane channels

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21
Q

What kind of process of facilitated diffusion?

A

A passive process

22
Q

What two types of proteins are involved in facilitated diffusion?

A

Protein channels

Carrier proteins

23
Q

Explain the use of protein channels in facilitated diffusion

A

Selective channels that open in the presence or a specific ion. There is control over the entry and exit of ions as the ions bind with the protein causing it to change shape so it opens on the other side

24
Q

What is the use of carrier proteins in facilitated diffusion?

A

The molecule binds with the protein causing it to change shape in such a way that releases the molecules on rhe other side

25
Q

Define osmosis

A

The movement of water from an area of higher water potential to an area of lower water potential through a selectively permeable membrane

26
Q

When it is not possible for …. to balance out the concentration of molecules water will move by …. the instead to balance out the water potentials

A

Diffusion

Osmosis

27
Q

How permeable is a cell wall?

A

Completely permeable

28
Q

How permeable is a cell surface membrane ?

A

Selectively permeable

29
Q

What does hypertonic mean in terms of water potential?

A

The water potential of the solution outside the cell is lower than the water potential inside the cell because the outside of the cell is more highly concentrated

30
Q

What does hypotonic mean in terms of water potential?

A

The water potential of the solution outside of the cell is higher than the inside of the cell because the outside is less highly concentrated than the inside

31
Q

Define solute

A

Any substance that is dissolved in a solvent i

32
Q

Define water potential

A

A measure of the ability of water molecules to move freely in solution

Pure water has a water potential of 0kPa
The more solute the lower the water potential will be

33
Q

Why can charged particles not cross a phospholipid bilayer easily ?

A

Water is a polar molecule and ions attract water molecules and become surrounded so they become too big to pass through the membrane so water cannot pass through so osmosis doesnt happen as much

34
Q

If there was a water potential of -200kPa and -400kPa would the water move towards the -200kPa or -400kPa?

A

-400kPa bc its more concentration

35
Q

When concentration is equal on either side… …. is established and there is no net movement of water

A

Dynamic equilibrium

36
Q

Why do you blot the outside if each cylinder of potato before weighing?

A

To remove the excess water on the outside of the potato because that can vary so it we need to ensure all the mass is the potato and the effect of osmosis

37
Q

Define active transport

A

The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins

38
Q

What is active transport used for?

A

Directly move molecules
Individually mice molecules using a concentration gradient which has already been set up called indirect active transport or co transport

39
Q

Is active transport a passive process?

A

No it requires metabolic energy in the form of ATP

40
Q

What types of proteins are used for active transport

A

Carrier proteins

41
Q

Describe the process of active transport

A

Carrier proteins that span the plasma membrane bind to the molecule or ion to be transported on one side of it
The molecule binds onto the receptor sites on the carrier proteins and ATP binds to the protein causing it to split into ADP and an inorganic phosphate molecule. This makes the carrier protein change shape and open on the other side of the membrane.
The phosphate is release from the protein which causes the protein to return to the original shape and ATP is made

42
Q

What is cotransport?

A

A form of active transport. It occurs when more than 1 molecule or ion is moved in the same direction or different direction at the same time

43
Q

Define indirect active transport

A

The transport of 1 substance coupled with the transport of another substance across a plasma membrane in the same direction through the same carrier protein

44
Q

Both sodium and …./ amino acid molecules move into the cell, but while sodium ions move …. the concentration gradient the glucose molecules move ….. the concentration gradient. It id the …. ion rather than the …. that directly powers the movement of glucose and amino acids into the cells. This makes it indirect rather than …

A 
Glucose
Down
Up
Sodium
ATP
Direct
45
Q

Is a cell wall semi permeable?

A

No it is completely permeable

46
Q

Is a phospholipid bilayer semi permeable?

A

Yes because it has carrier proteins and channel proteins

47
Q

Why is it important to wash the beetroot discs in the investigation about alcohol and beetroot?

A

To show that any pigment releases is from the effect of the alcohol

48
Q

What is a suitable control for the beetroot investigation?

What is the role of this control?

A

Have one made with just distilled water and 2 beetroot discs

To compare the results and ascertain that the results were due to the alcohol

49
Q

Why do you shake the tubes every minute?

A

To maintain a steep concentration gradient and prevent the discs from sticking together

50
Q

Why do you need to pour the alcohol away immediately ?

A

Because otherwise the diffusion would continue and we need to ensure they have all been in contact for the same amount of time

Biology (21 decks)

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