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PHGY 170 > Module 3 > Flashcards

Module 3 Flashcards

1
Q

the plasma membrane is semi permeable, what does that mean?

A

that means that some molecules can cross while others cannot. hydrophobic molecules and small uncharged molecules can freely diffuse while polar organic molecules, ions and proteins (hydrophilic compounds and large molecules) cannot diffuse

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1
Q

what is the structure of a phospholipid?

A
  1. head group - chemical properties determines where the phospholipid ends up in the membrane
  2. phosphate group - hydrophilic charged component
  3. glycerol - 3 carbon chain with 3 hydroxyl groups that is the backbone of the phospholipid
  4. fatty acid tails - 2 hydrocarbon chains that vary in composition and bond numbers which alters the rigidity
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2
Q

what are the two catagories of phospholipid head groups and what types are in each?

A
  1. polar - PI, PG, CL
  2. charged - PS (+, -), PE (+, right), PC (+, left)
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3
Q

what are the three other types of lipids in the membrane?

A
  1. cholesterol - has a hydroxyl group in one ring which interacts with the surface of the membrane, the rest of the molecule interacts with the lipid part
  2. glycolipids - have a sugar carbohydrate group attached to the lipid but no phosphate group and is involved in cell to cell signalling
  3. sphingomyelin (SM) - sphingosine backbone instead of glycerol and is common to myelin sheaths found wrapping around the axons of nerve cells
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4
Q

what are the four types of phospholipid clusters?

A
  1. micelles - when surrounded by water droplets with tails in the centre can be formed
  2. liposomes - when surrounded by water a tight bilayer with a hollow middle can be formed
  3. monolayer - on the boundary of water and atmosphere a single layer with heads toward the water is formed
  4. bilayer - in cells a bilayer is formed
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5
Q

what are the plasma membrane leaflets?

A

the phospholipid bilayer is referred to as leaflets.
1. facing the cytoplasm is called the cytosolic face or cytoplasmic leaflet
2. facing the exterior of the cell is the exoplasmic face or exoplasmic leaflet
(note - if an organelle has a double membrane the cytosolic face is on the exterior and interior)

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6
Q

what is the lipid asymmetry of the plasma membrane (what head groups are in each leaflet)?

A
  1. exoplasmic leaflet - positively charged phospholipids like PC and SM are a major component and glycolipids are present here. also some PS and PI present
  2. cytosolic leaflet - neutral and negatively charged phospholipids tend to be here like PS. positively polar PE is a major component
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7
Q

what is the purpose of lipid asymmetry?

A

it is used to maintain the function of the membrane and if the bilayer losses this organization it is a danger signal that can trigger the cells death

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8
Q

what are the three transporters that regulate phospholipid composition?

A
  1. floppases - keep most PC, sphingomyelin (SM) and cholesterol in the exoplasmic leaflet
  2. flippases - keep most PS, PE and PI in the cytosolic leaflet
  3. scramblases - briefly disrupts the membrane asymmetry by randomizing phospholipids
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9
Q

what is a concentration gradient?

A

it is formed when there is a difference between the concentration of a molecule on one side of the membrane compared to the other

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10
Q

how does water move through the membrane?

A

water can freely diffuse through the membrane with the help of aquaporins which are passive transport channel proteins that have a hydrophilic interior

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11
Q

what are the different tonicities of water?

A
  1. hypertonicity - a greater amount of solute outside the cell so water flows out (shrinks)
  2. hypotonicity - lower amount of solute outside the cell so water flows in (swells)
  3. isotonicity - equal amounts (ideal state)
    (note - low to high)
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12
Q

what are the two key elements of the revised fluid mosaic model?

A
  1. membrane constituents (phospholipids, cholesterol, proteins) join together to form complexes
  2. hydrophilic head groups interact with hydrophilic portions of membrane proteins
    (note - clusters of proteins, phospholipids, membrane constituents are called lipid rafts)
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13
Q

what are the four factors that affect membrane fluidity?

A
  1. temperature - increase flexible, decrease cooler rigid
  2. lipid contents - length of chains short (less than 16 carbon) more movement so more fluid, unsaturated has kinks leading to space increasing fluidity, saturated less movement
  3. cholesterol - acts as a spacer in lower concentration more fluid, high concentrations (50%+) makes the membrane more rigid
  4. protein - protein rich less movement so stiffer
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14
Q

what are the five types of membrane proteins?

A
  1. signalling - cell communication
  2. intergrins - membrane bound, facilitates cell adhesion and cytoskeleton movement
  3. receptors - facilitates endocytosis and exocytosis or used in cell signalling
  4. channel and transporters - move materials
  5. anchor and junctions - help cells move and attach to other cells and the extracellular matrix
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15
Q

what is passive transport?

A

membrane transport that does no require energy and molecules move down the gradient (high to low)
1. simple diffusion (gases) and facilitated diffusion
2. channel mediated transport - allows water and small ions to pass (some need a signal, aquaporins)
3. carrier mediated transport - conformational change to move cargo

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16
Q

what is active transport?

A

membrane transport that need energy (pump proteins need ATP) and molecules move against the gradient (low to high)
1. direct transport - used ATP directly (Na+ and K+)
2. indirect transport - does not directly use ATP but uses a gradient establish by direct active transport (Na+ and glucose)
3. symporters - move molecules in the same direction (Na+ and glucose)
4. antiporters - moves one molecule in and the other one out (Na+ in, Ca2+ out)

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17
Q

what is catabolism?

A

it is the break down of macromolecules and ATP stored within is released so it can be transferred to other molecules

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18
Q

what is anabolism?

A

it is the production of macromolecules and it consumes the ATP produced by catabolism

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19
Q

what is ATP composed of?

A

adenosine triphosphate is composed of an adenine molecule, ribose sugar and chain of 3 phosphates. there is energy stored between the bond of the second and third phosphates, so when the third is removed ADP is formed and energy is released

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19
Q

what is GTP?

A

guanosine triphosphate is identical to ATP by adenosine is replaced by guanosine

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20
Q

how are NAD+ and FAD converted into high energy molecules

A
  1. NAD+, a H+ ion and two electrons are added to form NADH
  2. FAD, two H+ ions and two electrons are added to form FADH2
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20
Q

what is the structure of the mitochondria?

A
  1. DNA - it has its own DNA to produce some proteins for ATP production
  2. cristae - inner membrane where enzymes convert high energy compounds into ATP (appears to be folded in on itself)
  3. matrix - inside of the mitochondria where macromolecules are converted into small high energy compounds (NADH)
20
Q

how is energy stored in carbohydrates?

A

they are stored mainly in glycogen in muscles and in the liver. muscle glycogen is more readily available for muscles as liver glycogen needs to be broken down into glucose to be secreted into the plasma. when there is extra glucose, glycogen stores are built up

20
Q

how is energy stored in fats?

A

it is stored as triacylgylcerols throughout the body but it must be broken down to release free fatty acids that need to be transported into the cells that need energy production

20
Q

how is energy stored in proteins?

A

it is stored mainly as skeletal muscles and is only used in extended fasting periods

20
Q

what are the classes of carbohydrates?

A
  1. monosaccharides - most commonly consumed in the form of glucose
  2. disaccharides - consists of two monosaccharides bonded by an alpha or beta 1-4 glycosidic linkage (lactose = galactose + glucose)
  3. polysaccharides - much long chains of monosaccharides (glycogen which is a storage molecules that must be broken down before it can be used to produce energy)
20
Q

how is glucose brought into the cell?

A

glucose enters the bloodstream from ingested food though de novo synthesis (formation of complex molecules in the body from simple molecules) in the body or from the breakdown of glycogen stores. once in the blood glucose circulates and is available for use. to get glucose into cells, glucose transporters are used

20
Q

what is glycolysis and why does it have a series of steps?

A
  1. it is the break down of glucose and the transfer of the energy produced to high energy electron carriers and ATP
  2. catabolic reactions are exothermic so a series of steps must occur as glucose has a lot of energy stored so it all the energy was released at the same time there would be lots of heat which would likely kill the cell
  3. multiple steps allows monosaccharides to enter glycolysis (do not have the same yield as glucose)
21
Q

explain the process of glycolysis

A
  1. one glucose molecule is converted into two glyceraldehyde 3 phosphate (G3P) molecules in the first five reactions, this required two ATP
  2. each G3P molecule enters the sixth and seventh reactions and is converted into 3 phospholglycerate (for each G3P 1 ATP and 1 NADH is produced)
  3. each 3 phosphoglycerate produces 1 pyruvate and 1 ATP
    (net of 2 ATP, 2 pyruvate and 2 NADH produced)
21
Q

what would happen if there was a build up in pyruvate?

A

if it were to build up to a sufficient concentration it is possible the conversion of glucose would stop and discontinue ATP production, to prevent this pyruvate is further processed. (dependent if oxygen is present)

22
Q

what is anaerobic respiration?

A

it occurs when there is an absence of oxygen in the cytoplasm. pyruvate undergoes fermentation so NADH can be oxidized to NAD+ (regenerated so glycolysis can reuse). produces one of two products
1. animal cells and bacteria - pyruvate is reduced to lactate
2. plant cells and yeast - pyruvate reduced to ethanol

23
Q

what are the five stages of aerobic respiration?

A

occurs in the presence of oxygen in the mitochondria
1. conversion of pyruvate to acetyl CoA
2. krebs cycle
3. the electron transport chain
4. chemiosmotic gradient
5. formation of ATP by ATP synthase

24
Q

explain the converting of pyruvate to acetyl CoA

A
  1. pyruvate in the cytosol is transported into the mitochondria
  2. carrier molecules on the inner mitochondrial membrane brings pyruvate into the matrix
  3. in the matrix pyruvate is decarboxylated by the pyruvate dehydrogenase complex
  4. the complex takes pyruvate, an NAD+ and a CoA molecule and converts them into acetyl CoA, NADH and CO2
    (note - one glucose yields two pyruvate so net energy production at this stage is 2 NADH)
25
Q

explain the krebs cycle

A
  1. acetyl CoA enters the cycle by combining with oxaloacetate to form citrate (6 carbon molecule)
  2. CoA is released (can be reused)
  3. citrate is broken down by several reactions to remove two of the carbons to create succinate
  4. the release of carbons transfer energy to two NAD+ to form two NADH, and are released in the form of two CO2 and one GTP (like ATP)
  5. succinate is converted back to oxaloacetate which released one NADH and one FADH2
26
Q

what is the total energy produced for the krebs cycle alone?

A

each acetyl CoA produces 3 NADH, 1 FADH2 and 1 GTP (ATP) so the the net is 6 NADH, 2FADH2 and 2 GTP (ATP)

27
Q

what is the total energy produced for the krebs cycle and glycolysis?

A

4 ATP, 10 NADH and 2FADH2 in total however 2 of the NADH are in the cytosol not the mitochondria. glycerol phosphate shuttle is a mechanism in the mitochondria that uses cytosolic NADH to produce FADH2, so in the mitochondria the total would then be 8 NADH, 4 FADH2 and 4 ATP

28
Q

what is oxidative phosphorylation?

A

it is the process used by the mitochondria to converts NADH and FADH2 into ATP. it refers to the ETC, the chemiosmotic gradient that it creates and the activity of ATP synthase

29
Q

explain the electron transport chain

A

it is a collection of protein complexes (four) and electron carriers found within the mitochondrial inner membrane. the purpose of the ETC is to use the energy of the energy carriers (NADH and FADH2) to pump protons into the inter membrane space
(note - NADH and FADH2 enter the ETC at different points, NADH enters first and moves more protons so generates more ATP). process also combines oxygen and protons to produce water

30
Q

what does complex I in the ETC do?

A

complex I - NADH coenzyme Q oxidoreductase uses electron from NADH to pump protons from the matrix to the inter membrane space

30
Q

what does complex II in the ETC do?

A

complex II - succinate coenzyme Q oxidoreducatse passes electrons from FADH2 to the ETC releasing protons into the matrix

30
Q

what does complex III in the ETC do?

A

coenzme Q cytochrome c oxidoreducatse uses electrons from both NADH and FADH2 to pump protons from the matrix to the intermembrane space

31
Q

what does complex IV in the ETC do?

A

complex IV 0 cytochrom c oxidase uses electrons from complex III to pump protons from the matrix to the inter membrane space

31
Q

what is the chemiosmotic gradient?

A

it is a proton gradient created across the inner mitochondrial membrane during ETC. protons are in high concentration to allow ATP synthase to generate ATP

32
Q

what does ATP synthase do?

A

ATP synthase is located within the inner membrane and uses the established proton gradient to phosphorylate ADP into ATP (chemiosomotic reaction). this occurs after protons have been pumped into the mitochondria via the ETC and ions are moved down their concentration gradient

32
Q

how much ATP is produced by NADH and FADH?

A
  1. NADH produces up to 3 but realistically 2.5
  2. FADH2 produces up to 2 but realistically 1.5
33
Q

what happens with excess ATP?

A

ATP is not very stable and there is no direct storage so creatine kinases converts creatine and ATP to create creatine phosphate and ADP. when ATP demand is high a reverse reaction occurs which does not need oxygen

33
Q

explain fat metabolism

A

it occurs in the mitochondria however fatty acids cant cross the membrane without help. fatty acid circulating the bloodstream called free fatty acids (FFA) are taken up into cells by a family of fatty acid transport proteins. once inside the cytosol they need to be activated in oder to be transported which is done by 2 ATP per FFA. in the mitochondria fatty acyl CoAs are metabolized by beta oxidation to produce high energy molecules (forms fatty acyl CoA ester)
(note - if the tail is short enough it can diffuse into the matrix, if long must be transported by a process called carnitine shuttle)

34
Q

how is fat metabolized by beta oxidation?

A

it breaks down fatty acids two carbons at a time to release acetyl CoA, each cycle releases energy in the form of 1 FADH2 and 1 NADH. to calculate net yield - (beta oxidation + krebs cycle - FFA activation)

35
Q

explain protein metabolism

A

nitrogen is removed by deamination and converted into a urea group and excreted in the urine as it cant be used to generate ATP. depending on the amino acid it can result in:
1. three carbon molecules used to synthesize glucose or enter glycolysis
2. formation of acetyl CoA
3. products that can enter as intermediaries of the krebs cycle

36
Q

what is the brains energy preference?

A

primary source is glucose but also get energy from ketones which are produced from the metabolism of fats in the liver

37
Q

what are ketones?

A

they are composed of a carbonyl group bonded with two hydrocarbon groups that are taken up by neurons and converted into acetyl CoA

38
Q

what is the hearts energy preference?

A

primary source is fatty acids although ketones can be used. (operates exclusively on aerobic respiration)

39
Q

what is skeletal muscles energy preference?

A

major sources are glucose, fatty acids (used primarily in resting muscles) and ketones. they have large stored of glycogen. heavy exercise leads to excess lactate which is excreted and may be converted back to glucose in the liver

40
Q

what sources of energy are used for different demands in muscles?

A
  1. low - stored fats as long as there is sufficient oxygen
  2. medium - stored carbohydrates or glycogen (converted to glucose)
  3. high - dependent on muscle glycogen, creatine phosphate used and proteins are used if all other options are used

PHGY 170 (4 decks)

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