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Clin Sci: Biology sms1 > Lec 7 and 8: Plasma Membrane, Transport and Organelles > Flashcards

Lec 7 and 8: Plasma Membrane, Transport and Organelles Flashcards

1
Q

what are the functions of the plasma membrane?

A
  • It regulates what enters and exits the cell, altering pH and charge
  • Is involved with cell recognition
  • Plays a major role in cell signalling e.g. from hormones
  • Has enzymatic functions
  • Aids in cell linking and cross-talk
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2
Q

*NOTE* image of plasma membrane

A
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3
Q

what does the lipid bilayer consist of?

A
  • Phospholipids (75%)
  • Cholesterol (20%)
  • Polar Glycolipids in the external layer (5%)
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4
Q

what is the role of cholestrol in the plasma membrane?

A
  • Cholesterol immobilises the first few hydrocarbon groups of the phospholipids molecules.
  • drecreases permeability to small water-soluble molecules
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5
Q

why is fluidity important for the plasma membrane?

A

•allows the movement of membrane components required for cell processes and formation of cellular junctions

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6
Q

what is the glycocalyx?

A

•glycoprotein’s containing covalently bonded to oligosaccharides

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7
Q

what are roles of membrane proteins?

A
  • Required for detection of ‘self’ in immunity
  • Aids in cell- cell adhesion
  • Makes RBCs slippery and protects the GI from drying out
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8
Q

If a membrane was depleted of cholesterol what would happen to the membranes structure?

A
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9
Q

Why do you think intracytoplasmic sperm injection doesn’t rupture the target egg cell?

A
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10
Q

what is the plasma membrane selectively permeable to?

A

•The lipid bilayer is permeable to non-polar molecules such as O2, CO2 and hormones

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11
Q

what is the plasma membrane impermeable to?

A

Ions and large molecules such as Na+ and glucose.

They need trans-membrane channel and carrier proteins

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12
Q

what is the plasma membrane slightly permeable to?

A

small uncharged polar molecules such as water

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13
Q

what is the importance of membrane permeablility?

A
  • allows cells to build concentration gradients
    e. g. O2and Na+ are more concentrated in the extracellular fluid: the opposite is true for K+ & CO2
  • pH can be regulated
  • membrane potential is created from electrical gradients
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14
Q

the inside of the cell is more positive or negative?

A

positve

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15
Q

what is passive transport and what are the different types?

A

passive transport = No cellular energy is used as substances move down their own concentration gradient.

types of passive transport:

– 1. Diffusion through lipid bilayer

– 2. Channel mediated facilitated diffusion

– 3. Carrier mediated facilitated diffusion

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16
Q

what are the two types of diffusion?

A

channel mediated diffusion: gated, timed or signal regulated

carrier mediated diffusion: subject to transport, maximum and saturation

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17
Q

How can insulin speed up the entry of glucose into the cell?

A

insulin facilitates the diffusion of glucose into cells

by up-regulating glucose transporters via its receptors

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18
Q

what is osmosis?

A

diffusion of water through a semi-permeable membrane.

diffusion through the lipid bilayer occurs through specific transmembrane protein channels called aquaporins

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19
Q

what is the difference between hypertonic, isotonic and hypotonic solutions?

In what clinical condition is a hypertonic solution used?

A

hypertonic: high water potential so water moves out of cells
isotonic: water potential is maintained so no net movement of water molecules
hypotonic: low water potential in cells so water moves into the cells

Infusion of hypertonic solution to relieve cerebral edema

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20
Q

what is active transport? what does it help to maintain?

A
  • process that uses energy from the hydrolysis of ATP
  • used to transport ions against their conc gradient

helps to maintain tonicity, volume and charge

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21
Q

what are the two types of active transport?

A

Primary active transport (uses energy from the hydrolysis of ATP)

Secondary active transport (uses energy stored by an ionic concentration gradient)

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22
Q

what is primary active transport?

give an example

A
  • Movement against a concentration gradient (mainly ions)
  • ATP changes the shape of the carrier protein, pumping the substance across
  • Most common example is sodium-potassium pump
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23
Q

what is secondary active transport (co-transport)?

A

where transporter protein couples the movement of an ion (Na+ or H+) down it electrochemical gradient

to the uphill movement another molecule or ion against a concentration/electrochemical gradient.

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24
Q

what is the difference between symport and antiport?

A
  • Symport is where the molecules travel in the same direction (used for Ca2+ regulation and H+ regulation)
  • Antiport is where they go in opposite directions
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25
Q

what is transcytosis?

A
  • Combination of endo and exocytosis
  • Substances are passed through a cell
  • Is common in endothelial cells which line the blood vessels
26
Q

what is vesicular transport used for?

A
  • endocytosis (bringing substances into the cell)
  • exocytosis (expelling from the cell, in secretory cells and nerve cells)
  • inter-organelle transport
27
Q

what are the 3 types of endocytosis?

A
  1. Receptor mediated endocytosis
  2. Phagocytosis and
  3. Pinocytosis
28
Q

what are the steps involve in receptor mediated endocytosis?

A

Process used for transporting LDL, vitamins and hormones

  1. Binding
  2. Vesicle formation
  3. Unseating
  4. Fusion with endosome
  5. Recycling of receptor
  6. Degradadtion in lysosomes
29
Q

what is clathrin?

A

•protein for enriching membrane domains

30
Q

what is phagocytosis?

A

where large particles (worn out cells and bacteria) are englufed

carried out by macrophages and neutrophils

31
Q

what are the steps involved in phagocytosis?

A
  • chemotaxis and adheremce of microbe to phagocyte
  • ingestiion of microbe of phagocyte
  • formation of phagosome
  • fusion of the phagosome with a lysosome to form a phagolysosome
  • digestion of ingestion microbe by enzymes
  • formation of residual body containign indigestible material
  • discharge of waste materials
32
Q

what is pinocytosis?

A

ingestion of droplets of extracellular fluid into a cell

without the use of receptors

It is non selective and occurs most in absorptive cells in the intestines and kidneys

33
Q

what are the types of cell junctions (5)?

A

Tight junctions

Adherens junctions

Desmosomes

Hemidesmosomes

gap junctios

34
Q

what do tight junctions do?

A

•prevent movement of substances

e.g cells lining the ddigestive tract

35
Q

what is the function of ahdereing junctions?

A

maintain cellular position and resist seperation in contracile acitivities

made up of plaque which attaches to the membrane proteins and the microfilaments of the cytoskeleton

36
Q

what are desomosomes and hemidesmosomes?

what is their function?

A
  • anchoring junctions held together by linker protein filaments called cadherins or integrins extending from button like thickenings called plaques.
  • Distributes tension and prevents tearing.

e.g. skin and heart muscle

37
Q

what are gap junctions?

what is their function?

A

hollow cylinders called connexons made of trans membrane proteins

they create gaps that connect animal cells

found in heart and smooth muscle tissue

38
Q

what are the two components within a cytoplasm?

A
  1. The cytosol (intracellular fluid)
  2. The organelles (specialised structure which co-operate to maintain homeostasis)
39
Q

what does the cyosol contain and what is it’s function?

A
  • Contains dissolved ions, glucose, amino acids, ATP, lipids and waste products
  • Is the site for a wide range of enzymatically controlled reactions
40
Q

what is the cytoskeleton?

A

a network of protein filaments extending throughout the cytoplasm

41
Q

what are the three main types of cytoskeleton?

A
  1. Microfilaments
  2. Intermediate filaments and
  3. Microtubules
42
Q

In the cytoskeleton what is the micro filament and what is does it do?

A

polymers of the proteins actin and myosin

that surround the edge of the cell

help generate movement, provide support needed for strength and shape

and create microvilli

43
Q

In the cytoskeleton what are the intermediate filaments? what is their function?

A

a family of proteins such as keratin, vimentin and lamin

found in the cell subject to mechanical stress

that help stabilise the position of the organelles

44
Q

In the cytoskeleton what are microtubules?

what is their function?

A

long unbranched hollow tubules made from tubulin

that form the centrosome

help with strength, shape and movement of organelles such as vesicles during division

provide structure to flagella

45
Q

what is the centrosome?

what is the function of the centrosome?

A

consist of 2 centrioles which are cylindrical structures composed of a circle of nine clusters of microtubule triplets, both at right angles to each other

for growth of mitotic spindle during cell division

46
Q

what is the difference in the centrosome in a cell that is is/is not undergoing division?

A
  • When a cell is not undergoing division, a single centrosome is present.
  • However, when the cell does begin to divide the centrosome replicates early in the process.
47
Q

what are cillia and flagella?

what are their function?

A

motile projections on cell surface made from microtubules

transport of fluid along cell surface

48
Q

what is each cilium anchored to?

how does smoking affecting cilia?

A

each cilium id anchored to the basal body

smoking destroys the cilia

causing a persistent cough to remove the build up mucus, dust and bacteria

causing female smokers to have an increase risk of an ectopic pregnancy

49
Q

*Note* difference between cilia and flagella

A

similar in structure but flagella are much longer and often only one is found on a cell

50
Q

what is the Endoplasmic reticulum?

A

•ER is a network of membranes in the form of flattened sacs and tubules extending from the nuclear envelope into the cytoplasm

51
Q

*NOTE* Rough ER

A

Rough ER contains ribosomes attached

Proteins made by the ribosomes enter the ER space for processing and sorting

52
Q

*NOTE* smooth ER

A
  • Extends from the rough ER
  • Contains no ribosomes but has a greater range of enzymes, making its functions more diverse
  • Synthesizes fatty acids and steroids such as estrogens and testosterone
  • In the liver it helps release glucose from gluc-6-p and detoxify lipid soluble drugs such as alcohol and pesticides
  • Stores Ca2+ ions in muscle
53
Q

what is the golgi complex

A

3-20 membranous cisternae(sac like structures) with bulging edges arranged in a stack.

The convex entry/cis face faces the ER and the concave exit/trans face faces the plasma membrane.

Sacs between are called medial cisternae

*trans=transports proteins away*

54
Q

explain the processing and packaging done by the golgi

A
  1. Proteins surrounded by ER membrane and transported through the cell
  2. Transport vesicles move to entry face
  3. Fusion of several vesicles crates the entry face and releases proteins
  4. Proteins are modified and move into medial cisternae, then either taken back to the entry face or to the exit face
  5. Within the exit face proteins are modified and packaged

6-9. Proteins sent to their destinations

55
Q

what is the function of a lysosome?

A

•Digestion of substances entering the cell, worn out organelles (autophagy) and entire cells (autolysis)

56
Q

what is the result of the absence of the lysosomal enzyme Hex A?

A

absence Hex A causes Tay- Sachs disease

  • Hex A normally breaks down a glycolipid prevalent in nerve cells
  • with its absence the glycolipid builds up destroying nerve cell function
  • patient suffers from seizures and muscle rigidity and become blind
57
Q

what are peroxisomes?

how are they different to lysosomes?

A

organelles that contain enzyme oxidases that metabolise amino acids, fatty acids and oxidise alcohol

contain enzyme catalase for protection against hydrogen peroxide

smaller than lysosomes

58
Q

what are three peroxisomal disorders?

A
  • Zellweger syndrome (ZS)
  • neonatal adrenoleukodystrophy (NALD)
  • rhizomelic chondrodysplasia punctata (RCDP),
59
Q

how proteasomes different from lysosomes?

A

proteasomes contain protease enzymes that degrade cytosolic proteins (uneeded proteins)

and are involved in negative feedback

where as lysosomes degrade proteins delivered in vesicles

60
Q

*NOTE* mitochondria

A
61
Q

*NOTE* nucleus

A
62
Q
A

Clin Sci: Biology sms1 (11 decks)

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