Molecular Cell Base Part 2 Flashcards Preview

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Flashcards in Molecular Cell Base Part 2 Deck (56)
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1
Q

Do the majority of biochemicals pass through the lipid bilayer?

A

NO

2
Q

What substances can cross the lipid bilayer?

A

Lipid-soluble sources AND

Water (too small)

3
Q

Extra cellular fluid contains:

A

Na+ and Cl-

4
Q

Intracellular fluid contains:

A

K+, Phosphate, and proteins

5
Q

What is imprortant for membrane transport?

A

Membrane proteins

6
Q

What two things can membrane proteins act as?

A
  1. Channels

2. Carrier proteins

7
Q

Are channels and carrier proteins selective or non selective?

A

Usually selective

8
Q

Transport through the cell membrane occurs via what two processes?

A
  1. Passive Transport or Diffusion

2. Active Transport

9
Q

What is passive transport (diffusion)

A

When molecules move down their concentration gradient

Does not require the cell to expend energy

10
Q

What type of energy does passive transport/diffusion use if not cell provided energy?

A

Kinetic energy

11
Q

What is active transport?

A

Molecules move down their concentration gradient

12
Q

What energy does active transport use to move molecules?

A

The cell’s energy

13
Q

What are the main two types of passive transport?

A
  1. Simple diffusion

2. Facilitated diffusion

14
Q

What is simple diffusion?

A

Molecules diffuses through the lipid bilayer by:

  1. Selective protein channels
  2. Gated Channels
  3. Osmosis
15
Q

What is facilitative diffusion?

A

Diffusion through

  1. Carriers or
  2. Transporters
16
Q

Regarding simple diffusion, what is the rate of diffuion directly proportional to?

A

It is directly proportional to lipid solubility of the molecule

17
Q

WHat molecules can dissolve by simple diffusion directly?

A

Oxygen Nitrogen CO2 and alcohol

18
Q

What TYPE of molecules readily dissolve in lipid bilayers?

A

Small hydrophobic molecules

O2, CO2

19
Q

What TYPE of molecules dissolve more slowly across lipid bilayers?

A

Small uncharged hydrophilic molecules

H20, Urea, glycerol

20
Q

What TYPE of molecules are impermeable to the lipid bilayer?

A

Ions, they will not cross the lipid bilayer no matter how small they are

21
Q

Protein channels are usually highly selective: true or false?

A

TRUE

22
Q

What usually determines selectivity in protein channels?

A
  1. Diameter
  2. Shape
  3. The nature of the electrical charge or bonds along the inside surface
23
Q

What is an example of a selective protein channel?

A

Potassium channel

24
Q

How does the potassium channel permit potassium ions to pass?

A

A narrow selective filter has transient binding sites for potassium which allows passage of the ions

25
Q

For gated channels, what controls ion permeability?

A

The gate

26
Q

What kind of stimuli can open ion gated channels?

A
  1. Changes in voltage across a membrane
  2. Ligand (intracellular or extracellular)
  3. Mechanical stress
27
Q

Voltage gated channels are present in the plasma membrane of what type of cells?

A

All excitable cells

28
Q

What are some types of excitable cells?

A
  1. Nerve cells
  2. Muscle cells
  3. Endocrine cells
  4. Egg cells
29
Q

What is the job of voltage gated channels in nerve cells?

A

Voltage gated channels:

  1. Responsible for the neurons ability to transmit information along its length
  2. Release neurotransmitters

….in neurons

30
Q

What causes voltage gated channels to open?

A

A range of membrane potentials

31
Q

In regards to voltage gated channels,

What is a “channel’s threshold”?

A

A channel’s threshold = the minimum membrane potential needed to open the channel

32
Q

Where are ligand gated channels found?

A

Ligand gated channels are found:

  1. In the membrane of skeletal muscle cells
  2. Some neurons of the autonomic Nervous System and the brain
33
Q

How do ligand gated channels open?

A

Via ligand binding

34
Q

What is another name for facilitated diffusion?

A

Carrier mediated diffusion

35
Q

Properties of Facilitated Diffusion:

A
  1. Specific proteins facilitate diffusion across a membrane
  2. No cellular energy required
  3. The carrier only acts on specific substrates
  4. The rate of transport will reach a maximum based on the number of proteins available for transport
36
Q

In facilitated diffusion, can the rate of diffusion rise higher than the Vmax of the carrier protein?

A

NO

37
Q

What is the difference between the rate of simple diffusion and facilitated diffusion?

A

In simple diffusion the rate of diffusion is proportional to the concentration of the diffusing substance whereas in facilitated the rate of diffusion is never greater than the Vmax of the carrier protein

38
Q

What is osmosis?

A

The net movement of water caused by a difference in water concentration across a membrane

39
Q

What are the two ways water diffusion typically occurs?

A
  1. Diffusion through the lipid bilayer (unaided) (simple diffusion)
  2. Through selective protein channels (simple diffusion) called “Aquaporins”
40
Q

Are aquaporins highly specialized? And are there different types?

A

Yes they are highly specialized, and yes there are at least 13 types in various mammalian cells

41
Q

What other factor can also influence the diffusion of water?

A

Pressure

42
Q

What is osmotic pressure?

A

The amount of pressure required to stop OSMOSIS is osmotic pressure.

Remember: osmosis is the diffusion of water across the membrane or through aquaporins

43
Q

What are the two main types of active transport?

A
  1. Primary active transport

2. Secondary active transport

44
Q

What is primary active transport?

A
  1. The energy is derived directly from ATP or something similar
  2. Transport is against the concentration gradient or electrochemical gradient
45
Q

What is secondary active transport?

A
  1. The energy is provided by the concentration gradient of the driving ion
  2. Transporter proteins couple the movement of an ion going down its concentration gradient (usually Na+ or H) with an ion or molecule moving against its concentration gradient
    - uses “CoTransport” or “Counter transport”
46
Q

What is co-transport (secondary active transport)?

What is the membrane protein called in this situation?

A

The simultaneous transport of two substances across a membrane in the SAME direction
-one is moving with its concentration gradient, the other is moving against

The membrane protein used is called a “Symporter”

47
Q

What is another name for Co-transport (secondary active transport)?

A

Symport

48
Q

What is another name for counter transport (secondary active transport)?

A

Anti port

49
Q

What is counter-transport (secondary active transport)?

What is the membrane protein called in this situation?

A

The simultaneous transport of two substances across a membrane in OPPOSITE directions.
-one is moving with its concentration gradient the other is moving against

The protein is called an antiporter.

50
Q

What is transcellular transport or epithelial transport?

A
  • Substance is carried across the cell

- from one ECF to another

51
Q

What is the mechanisms used to cross the cell membrane to get to the other ECF in transcellular transport?

A

One side uses active transport

The other side of a membrane uses simple diffusion or facilitated

52
Q

What is the other method of transporting molecules across the membrane by means other than membrane proteins, where the membrane itself is a carrier?

A

Exocytosis

Endocytosis

53
Q

What are the 3 types of Endocytosis and what is their main function?

A
  1. Phagocytosis
    • Ingestion of large molecules
  2. Pinocytosis
    • Ingestion of small molecules
  3. Receptor-mediated endocytosis
    • ex: cholesterol
54
Q

What are the two types of secretion associated with exocytosis?

A
  1. Constitutive secretion

2. Regulated secretion

55
Q

Properties of constitutive secreted exocytosis:

A
  1. All cells
  2. No signal sequence
  3. Proteins are incorporated into plasma membrane, extracellular matrix, or signaling proteins
56
Q

Properties of regulated secretion of exocytosis:

A
  1. Specialized cells

2. Need signal to stimulate fusion with cell membrane and release of secreted proteins