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PHYSL 200 > Cell Physiology > Flashcards

Cell Physiology Flashcards

1
Q

What is the plasma (cell) membrane?

A

Surrounds the cell surface
- separating the intercellular fluid from extracellular environment/extracellular fluid

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2
Q

What are cell organelles?

A
  • Perform specific functions and compartmentalize the cell
  • can be membrane bound and non-membrane bound
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3
Q

What are the main components of the cell?

A
  • nucleus
  • cytoplasm (region outside the nucleus) that contains organelles and cytosol (gel-like fluid)
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4
Q

What are the functions of the plasma (cell) membrane?

A
  • physical barrier
    • keeps organelles and proteins inside cell
    • maintains difference in fluid composition between ECF/ICF (maintains ionic composition)
    • maintains homeostasis
  • cell-to-cell communication
    • contains receptors that bind specific signalling molecules arriving at the cell surface
  • structural support
    • specialized connections between plasma membrane or between membranes and extracellular materials
  • transport (in and out of cell)
    • selectively permeable
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5
Q

True or False: All biological membranes are made the same

A

False: Biological membranes are not all made the same
- each can have a different ratio of lipid and proteins
- each ratio reflects a different function of the cell or organelle

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6
Q

What are lipids?

A
  • primarily made of carbon and hydrogen (linked by non-polar / neutral covalent bonds)
  • most contain oxygen and some contain phosphates (may provide polarity depending on structure)
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7
Q

What are the 3 main types of membrane lipids?

A
  • phospholipids
  • cholesterol
  • glycolipids
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8
Q

What are the key characteristics of phospholipid structure?

A
  • amphipathic (polar head group and non-polar tail)
  • polar head group = hydrophilic
    > phosphate attached to glycerol
    > nitrogen-containing chemical group (R)
    > glycerol backbone
  • non-polar tail = hydrophobic
    > 2 fatty acid chains (carbon and hydrogen)
    > saturated (single bond)
    > unsaturated (double bond)
  • spontaneously form bilayer
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9
Q

What is an important steroid lipid found in cell membranes? And what is its structure? And what is its function?

A

1) Cholesterol
2) Structure:
- contains 3 six carbon rings
- 1 five carbon ring
- C-H chemical group attached to one of the rings (non polar)
- single polar hydroxyl group
3) Function:
- amphipathic
- prevents fatty acid chain from packing together and crystallizing to maintain membrane fluidity

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10
Q

What are glycolipids?

A
  • lipids with CHO chain attached
  • outer leaflet of plasma membrane
  • amphipathic (polar and non-polar regions)
  • form glycocalyx
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11
Q

What is the glycocalyx?

A
  • layer of carbohydrates linked to lipids
  • helps cell with identification and interaction between cells
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12
Q

What are the three main types of membrane proteins?

A

1) Integral:
- amphipathic
- transmembrane proteins (exposed to cytosol and extracellular fluid, can span bilayer once or more than once)
2) Peripheral:
- not amphipathic
- inner/outer surface of membrane (most on cytosolic side)
3) Glycoproteins
- protein with attached carbohydrates
- located on extracellular surface of plasma membrane (also help form glycocalx)

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13
Q

True or False: All proteins are distributed unequally in the cell membrane.

A

True: Asymmetry is related to the function of a cell

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14
Q

what is considered the smallest cell of the body and why is it small

A

the red blood cell and it helps with surface area

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15
Q

what is cytosol made of

A

proteins, electrolytes and water

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16
Q

what are the most abundant type of membrane lipids

A

phospholipids

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17
Q

true or false - glycoproteins form glycocalyx

A

true

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18
Q

what are the three types of desomosomes

A

cadherins, plaques and intermediate filaments

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19
Q

_____ are cell junctions that are found in areas that are exposed to a lot of tension and stretching

A

desmosomes

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20
Q

_____ are a type of desmosome that links cells together

A

cadherins

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21
Q

where can tight junctions be found

A

in epithelial cells and intestines

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22
Q

what is an example of a tight junction and what is their importance

A

occludins; limit movement of structures inside and outside the cell as well as form impermeable junctions

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23
Q

what is the importance of gap junctions

A

they are transmembrane channels that directly connect the cytoplasms of two cells

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24
Q

where are gap junctions found

A

mainly the heart, cardiac muscle

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25
Q

what is the largest organelle in the body

A

nucleus

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26
Q

what are the two organelles that have double layered porous membrane

A

mitochondria and nucleus

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27
Q

where does the synthesis of ribosomal RNA occur

A

nucleolus

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28
Q

true or false - skeletal muscle cell has no nucleus

A

false - it is multinucleate

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29
Q

what are ribosomes responsible for

A

protein synthesis

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30
Q

what are the two types of ribosomes and where are they found

A

free - in cytoplasm
bound - ER

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31
Q

what is the difference between rough and smooth ER

A

rough ER has ribosomes attached to its surface whereas smooth ER does not

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32
Q

pick the odd one out and replace it with the right answer

the smooth ER has these three functions
- stores calcium, synthesizes proteins and detoxifies drugs

A

it does not synthesize proteins, it synthesizes lipids - only the rough ER synthesizes proteins

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33
Q

what is the name of the curved membrane bound sacs in the Golgi apparatus

A

cisternae

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34
Q

true or false - lysosomes do not function at an acidic pH

A

false - they do

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35
Q

what are the two functions of lysosomes

A
  1. breakdown macromolecules into their subunits using hydrolytic enzymes
  2. destroy debris such as viruses and bacteria
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36
Q

what structure provides the mitochondria with a lot of surface area

A

cristae

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37
Q

true or false - mitochondria have their own DNA

A

true

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38
Q

what are examples of structures with lots of mitochondria

A

skeletal and heart muscle, sperm

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39
Q

what are the three ways of endocytosis

A

phagocytosis, pinocytosis and receptor-mediated endocytosis

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40
Q

what kind of substances does pinocytosis take up

A

small molecules, ions and nutrients

41
Q

put the steps of phagocytosis in order

pseudopodia, attachment, destruction, formation of phagolysosome, recognition, release

A

recognition, attchment, psudopodia, formation of phagolysosome, destruction then release

42
Q

what is the name of the vesicle formed from receptor-mediated endocytosis and what are its three functions

A

clathrin-coated vesicle
1. deposit contents into lumen
2. fuse with plasma membrane to release contents
3. fuse with endosomes so that the contents can be sorted to where they need to go

43
Q

if phagocytosis is not able to digest the substance , what happens

A

exocytosis

44
Q

what are the functions of exocytosis

A
  1. secrete specific substances
  2. release waste
  3. replace the portions of plasma membrane that were removed by endocytosis
45
Q

pick the odd one out and replace it with the correct answer

  1. chemical
  2. mechanical
  3. electrochemical
A

mechanical -> electrical

46
Q

what drives a chemical driving force

A

concentration gradient with different concentrations on other side

47
Q

true or false - molecules flow from high to low concentration

A

true

48
Q

how does the electrical driving force work

A

ion experiences attractive or repulsive forces due to the membrane potential

49
Q

what does the direction of the electrochemical driving force depend on

A

on the net direction of electrical and chemical driving forces

50
Q

what are examples of molecules that can pass through simple diffusion

A

co2, O2, fatty acids and ethanol

51
Q

what is the most favorable characteristics of molecules that can pass through simple diffusion

A

non polar, uncharged and small

52
Q

true or false - ions can pass through simple diffusion

A

false - they have a charge

53
Q

direction of simple diffusion flow

A

high to low concentration

54
Q

what are the three factors influencing the rate of simple diffusion

A

magnitude of driving force, surface area and membrane permeability

55
Q

true or false - the smaller the surface area, the greater the rate of simple diffusion

A

false - *the greater the surface area

56
Q

how does the diffusing distance affect the rate of simple diffusion

A

the rate of diffusion is inversely proportional to distance

57
Q

true or false - the higher the temperature the greater the rate of diffusion

A

true

58
Q

briefly explain passive transport

A

it is a type of mediated transport where molecules move through carriers or channels, down a concentration gradient with a help of a protein

59
Q

are mediated transporters specific or non specific

A

specific

60
Q

what is the direction of net flux for carrier mediated diffusion

A

high to low concentration

61
Q

what determines the ion flux in channel mediated diffusion

A

electrochemical gradient

62
Q

what are the three types of gates involved in channel mediated facilitated diffusion

A

voltage, ligand and mechanical

63
Q

other than passive transport, what is another example of mediated transport

A

active transport

64
Q

true or false - active transport does not require energy

A

false - it does, for example ATP

65
Q

active transport moves ____ its concentration gradient and from ____ to ____ concentration

down/against ; high/low

A

against ; low to high

66
Q

in primary active transport, what is the net charge as calcium and potassium are being transported

A

+1

67
Q

3 ___ out, 2 ___ in per ATP that is hydrolyzed

A

Na+, K+

68
Q

what are the concentrations of the sodium and potassium once the gradient has been created

A

high Na outside and high K inside

69
Q

what is the name of the enzyme that helps create the concentration gradient in primary active transport

A

Na/K ATPase

70
Q

what is the energy source of secondary active transport

A

the electrochemical gradient

71
Q

how does the process of secondary active transport work

A

as one ion moves down its electrochemical gradient, it couples the movement of another molecule to move against the gradient

72
Q

what is the name for two substances transported in the same direction

A

cotransport/symport

73
Q

what is an example of an antiport

A

Na/H exchanger

74
Q

what is an example of a symport

A

Na/glucose cotransporter

75
Q

match the term to the transporter

electrogenic and electroneutral
symport and antiport

A

electrogenic and symport
antiport and electroneutral

76
Q

what does it mean when a transport is saturable

A

mediated transport is saturable because there a finite/limited number of binding sites and protein transporters

77
Q

true or false - simple diffusion is non saturable

A

true because it does not need to compete for protein transporters and there is no limitation

78
Q

what are the two types intercellular communication

A

direct and indirect

79
Q

what is an example of direct intercellular communication

A

gap junctions

80
Q

what is an example of indirect intercellular communications

A

lipid soluble or insoluble chemical messengers

81
Q

what are transcription factors

A

alters transcription of mRNA by binding to a specific sequence of DNA at the beginning of the gene

82
Q

what is the term used for the specific sequence of DNA near the beginning of a gene

A

response element

83
Q

true or false - membrane bound receptors are hydrophobic

A

false - they are hydrophillic because they are water soluble

84
Q

what is the name of the enzyme that phosphorylates another protein

A

protein kinase

85
Q

what does a first messenger do

A

it is an extracellular chemical messenger that binds to a specific membrane receptor

86
Q

how does the second messenger system work

A

it is a substance that is generated in the cytoplasm of a cell in response to the binding of an extracellular messenger

87
Q

what are the three subunits of G proteins

A

alpha, beta and gamma

88
Q

true or false - GDP and GTP are low energy bonded molecules

A

false - they are high energy molecules

89
Q

describe the process of G linked receptor activation

A

1) membrane bound receptor is bound to the G protein subunits on the inside of cell ; while the ligand binds to the receptor on the outside of cell
2) the alpha subunit is directly bound to the GDP
3) as this happens the G protein changes its structure - the GDP is replaced by GTP and the subunits unbind from the receptor
4) the alpha subunit is then activated and separates from the beta and gamma subunits , with its new GTP
5) these keeps happening as long as there is no phosphorylation

90
Q

describe the process of G linked receptor inactivation

A

1) currently, the alpha subunit is bound to GTP but separated from the other subunits
2) when the ligand unbinds from the receptor, GTPase comes in and removes a phosphate from the GTP (hydrolytic activity)
3) all the subunits bind back together and bind to the membrane bound receptor once again

91
Q

what is the result of the action of G proteins on Ion channels

A

once the alpha subunit and bound GTP are dissociated, it will move to an ion channel and allow it to open/close

92
Q

what is the result of the action of G proteins on an enzyme

A

once the alpha subunit and bound GTP has dissociated, it will move to the enzyme where the stimulatory G protein will stimulate enzyme or the inhibitory G protein will inhibit it

93
Q

Describe the Action of G-Proteins on Ion Channels

A

1) the first messenger ligand binds to it’s target receptor - causes a conformational change in the receptor
2) the alpha-subunit’s affinity for GDP decreases and affinity for GTP increases (GDP dissociates and GTP binds)
3) the now GTP and alpha subunit dissociates from the beta and gamma counterparts - GTP alpha subunit moves towards the ion channel
4) depending on previous state of ion channel, it may open or close in response to the GTP-alpha subunit (ion channel will alter the flow of ions into the cell and can affect the electric potential)

94
Q

Describe the action of G-proteins on Enzymes

A

1) the first messenger ligand binds to it’s target receptor - causes a conformational change in the receptor
2) the alpha-subunit’s affinity for GDP decreases and affinity for GTP increases (GDP dissociates and GTP binds)
3) the now GTP and alpha subunit dissociates from the beta and gamma counterparts - GTP alpha subunit moves towards the enzyme
4) GTP alpha subunit can become a stimulatory protein (G_s) or an inhibitory protein (G_i)
5) Gs and Gi alter the production of the second messenger (amplifier) in cytosol of cell

95
Q

Gs _____________ the cAMP second messenger system, while Gi _____________ the cAMP second messenger system.

activates; inhibits
inhibits; activates

A

activates; inhibits

Gs activates the cAMP second messenger system (STIMULATORY), while Gi inhibits the cAMP second messenger system (INHIBITORY)

96
Q

Describe the cAMP second messenger system

A

1) Binding of the first messenger ligand to the receptor causes a conformational change in the receptor
2) the affinity for the alpha subunit for GTP increases (causing GTP to bind and GDP to dissociate)
3) GTP bound alpha subunit dissociates from beta and gamma subunits and moves towards enzyme: adenylyl cyclase
4) adenylyl cyclase is activated (via activation site located on cytoplasmic side of plasma membrane)
5) adenylyl cyclase catalyzes cytosolic ATP -> turns it into cyclic AMP (cAMP)
6) cAMP (second messenger) diffuses through the cytoplasm, binds and activates protein kinase A (PKA)
7) activated PKA catalyzes the phosphorylation of proteins in cell by transferring a phosphate group from ATP to cellular proteins
8) when cellular protein has been phosphorylated -> cellular response
9) cellular response eventually deactivated by conversion of cAMP to non-cyclic AMP via phosphodiesterase

97
Q

Describe how a ligand-gated ion channel would impact Ca2+ levels

A

Ligand gated ion channel would undergo a conformational change when activated and allow Ca2+ to enter the cell

98
Q

Describe how a G-protein would affect Ca2+ levels

A

1) Once G-protein is activated, it would interact with its effector protein (e.g. calcium channel)
2) calcium channel opens
3) Calcium enters the cell

99
Q

Describe how calcium is used to develop a cellular response

A

1) first messenger binds to receptor and causes an increase in calcium entry through the plasma membrane calcium channels
2) receptor is either a ligand gated ion channel or is a G-protein
3) once receptor is activated -> increase in Ca2+ in cytosol
4) Ca2+ in cytosol binds to receptors on ER membrane, ion channel opens, calcium flows out of ER, triggers more calcium release from ER and increases cytosolic [Ca2+] (calcium moves down it’s concentration gradient)
5) when calcium levels inside the cell become high enough, calcium acts as a second messenger
6) calcium binds to inactive calmodulin and activates calmodulin
7) calcium-calmodulin complex activates a calmodulin dependent protein kinase -> phosphorylates proteins in cell -> cellular response!

PHYSL 200 (17 decks)

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