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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

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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
what is transcytosis?
* Combination of endo and exocytosis * Substances are passed through a cell * Is common in endothelial cells which line the blood vessels
26
what is vesicular transport used for?
- endocytosis (bringing substances into the cell) - exocytosis (expelling from the cell, in secretory cells and nerve cells) - inter-organelle transport
27
what are the 3 types of endocytosis?
1. Receptor mediated endocytosis 2. Phagocytosis and 3. Pinocytosis
28
what are the steps involve in receptor mediated endocytosis?
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
what is clathrin?
•protein for enriching membrane domains
30
what is phagocytosis?
where large particles (worn out cells and bacteria) are englufed carried out by macrophages and neutrophils
31
what are the steps involved in phagocytosis?
- 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
what is pinocytosis?
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
what are the types of cell junctions (5)?
Tight junctions Adherens junctions Desmosomes Hemidesmosomes gap junctios
34
what do tight junctions do?
•prevent movement of substances e.g cells lining the ddigestive tract
35
what is the function of ahdereing junctions?
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
what are desomosomes and hemidesmosomes? what is their function?
* 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
what are gap junctions? what is their function?
hollow cylinders called connexons made of trans membrane proteins they create gaps that connect animal cells found in heart and smooth muscle tissue
38
what are the two components within a cytoplasm?
1. The cytosol (intracellular fluid) 2. The organelles (specialised structure which co-operate to maintain homeostasis)
39
what does the cyosol contain and what is it's function?
* Contains dissolved ions, glucose, amino acids, ATP, lipids and waste products * Is the site for a wide range of enzymatically controlled reactions
40
what is the cytoskeleton?
a network of protein filaments extending throughout the cytoplasm
41
what are the three main types of cytoskeleton?
1. Microfilaments 2. Intermediate filaments and 3. Microtubules
42
In the cytoskeleton what is the micro filament and what is does it do?
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
In the cytoskeleton what are the intermediate filaments? what is their function?
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
In the cytoskeleton what are microtubules? what is their function?
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
what is the centrosome? what is the function of the centrosome?
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
what is the difference in the centrosome in a cell that is is/is not undergoing division?
* 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
what are cillia and flagella? what are their function?
motile projections on cell surface made from microtubules transport of fluid along cell surface
48
what is each cilium anchored to? how does smoking affecting cilia?
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
\*Note\* difference between cilia and flagella
similar in structure but flagella are much longer and often only one is found on a cell
50
what is the Endoplasmic reticulum?
•ER is a network of membranes in the form of flattened sacs and tubules extending from the nuclear envelope into the cytoplasm
51
\*NOTE\* Rough ER
Rough ER contains ribosomes attached Proteins made by the ribosomes enter the ER space for processing and sorting
52
\*NOTE\* smooth ER
* 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
what is the golgi complex
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
explain the processing and packaging done by the golgi
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
what is the function of a lysosome?
•Digestion of substances entering the cell, worn out organelles (autophagy) and entire cells (autolysis)
56
what is the result of the absence of the lysosomal enzyme Hex 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
what are peroxisomes? how are they different to lysosomes?
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
what are three peroxisomal disorders?
* Zellweger syndrome (ZS) * neonatal adrenoleukodystrophy (NALD) * rhizomelic chondrodysplasia punctata (RCDP),
59
how proteasomes different from lysosomes?
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
\*NOTE\* mitochondria
61
\*NOTE\* nucleus
62

Clin Sci: Biology sms1 (11 decks)

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