EXAM 2 Flashcards
(136 cards)
1
Q
What is the final electron acceptor of ETC
A
Oxygen
2
Q
What are two ways to move electrons on NADH from cytoplasm into mitochondria? List the differences
A
Malate/ Aspartate shuttle
- completely reversible
- cytoplasmic NADH → 3 ATP
Glycerol phosphate shuttle
- irreversible
- cytoplasmic NADH → 2 ATP
3
Q
where does electron transport and oxidative phosphorylation occur?
A
Inner mitochondrial membrane
4
Q
The inner membrane is permeable only to
A
- H2O
- CO2
- O2
(everything else must have a transporter)
5
Q
What enzyme of TCA is also part of the ETC , specifically Complex II, found in the IMM
A
Succinate DH
6
Q
when will the malate aspartate shuttle be active
A
in a relaxed state
7
Q
when will the glycerophosphate shuttle be active
A
active when we need to make ATP as fast as possible ( doing physical activity)
8
Q
What energy sources are being used in the cytoplasm vs IMM during the glycerol phosphate shuttle?
A
NADH in cytoplasm and FADH2 in IMM
9
Q
How does the Km and Vmax look like when Ca2+ pours in from cytoplasm → mitochondria vs mitochondria → cytoplasm?
A
cytoplasm ➜ mitochondria:
↑ Km
↑ Vmax
mitochondria → cytoplasm:
↓ Km
↓ Vmax
10
Q
What happens to Ca2+ levels in the cytoplasm during muscle contraction?
A
Ca2+ levels increase
11
Q
Why does Ca²⁺ need to enter the mitochondria during muscle contraction?
A
To activate pyruvate dehydrogenase (Pyr DH) and the TCA cycle
12
Q
Electron transport oxidation vs reduction
A
oxidation:
NADH + H⁺ → NAD⁺ + 2e⁻ + 2H⁺
reduction:
1/2 O₂ + 2e⁻ + 2H⁺ → H₂O
13
Q
ETC
A
14
Q
How do you calculate ∆E’ in ∆G’ = -nF(∆E’)
A
E’(acceptor) - E’ (donor)
15
Q
Explain the general mechanism for ETC
A
(NADH in mitochondria) drop it into Complex I and pump 4H⁺ OUT, hand it off to Coenzyme Q, which will take it to Complex III (4H⁺), hand it to Cytochrome C → complex IV (2H⁺)
16
Q
how many protons total are pumped out of the mitochondria?
A
10 H⁺ total
4- complex I
4- complex III
2- complex IV
17
Q
Explain what is oxidized/ reduced in each complex
A
Complex I
reduced by: NADH
oxidized by: coenzyme Q
Complex III
reduced by: QH2
oxidized by: Cyt C
Complex IV
reduced by: Cyt C
oxidized by: O2
18
Q
What ion is needed in Complex IV and what is the disease name for the lack of this ion?
A
Copper; Menke’s disease
19
Q
Draw Q, QH*, QH2 structures
A
lec 5, slide 26
20
Q
What does Q cycle allow for?
A
Allows complex III to transport 4 H⁺ with only 2e-
21
Q
___prosthetic groups are used for high energy electrons in ETC
A
Iron sulfur
22
Q
Explain the Q cycle
A
Step 1: Two Electrons from Ubiquinol (QH₂)
Ubiquinol (QH₂), which carries two electrons, enters Complex III.
QH₂ donates its two electrons:
One electron goes to cytochrome c (which can only accept one electron at a time).
The other electron goes to another molecule of ubiquinone (Q), converting it into a partially reduced intermediate called semiquinone (Q*⁻).
At the same time, QH₂ releases two protons (H⁺) into the intermembrane space (this is part of the proton gradient formation).
Step 2: Second Ubiquinol (QH₂) Enters
A second QH₂ molecule enters Complex III and donates its two electrons.
Again, one electron goes to another cytochrome c molecule.
The second electron goes to the previously formed semiquinone (Q*⁻), fully reducing it to ubiquinol (QH₂).
Step 3: Protons and Electron Transfer
The two cytochrome c molecules (each carrying one electron) move on to Complex IV.
Two more protons (H⁺) are pumped into the intermembrane space from the second QH₂.
Net Result:
✦2 electrons are transferred to 2 cytochrome c molecules
✦4 protons (H⁺) are pumped into the intermembrane space.
✦1 molecule of ubiquinol (QH₂) is oxidized, and 1 molecule of ubiquinone (Q) is regenerated.
23
Q
Complex IV Cytochrome C oxidase pumps ___ H⁺/e⁻ across mito. inner membrane but always works in batches of ___e⁻
A
2; 4
24
Q
1 round of the TCA cycle pumps __H⁺ across the membrane
A
36
25
citrate→succinate via TCA cycle produces___ATP worth of energy
7
26
1 round of the TCA cycle in cells treated with amytal pumps___ H⁺ across the membrane
6
27
List the four basic rxns involving free radicals
✭O₂ + 1 e⁻ → O₂⁻ (superoxide radical)
✯O₂ + 1 e⁻ + 2H⁺ → (hydrogen peroxide)
✭ H₂O₂ + 1e- → OH⁻ + *OH (hydroxyl radical)
✯ H⁺ + *OH + 1e⁻ → **H2O**
28
draw the TCA cycle including its intermediates (NADH, FADH₂)
lec 4, slide 50
29
name the enzyme in which the mechanism involves a hydride removal by FAD
Succinate DH
(succinate→fumarate)
30
alcohols have higher/lower energy/
lower
NADH (3 ATP *2.5)
FADH₂ (2ATP *1.5)
31
How many protons does the ETC push out (NAD vs FAD)?
**NADH** :10 protons.
**FADH₂** : 6 protons.
32
What is the significance of the Glycerol Phosphate shuttle?
Glycerol Phosphate Shuttle is irreversible, feed electrons from cytoplasmic NADH directly into the mitochondria electron transport chain, and results in 2 ATP per NADH
33
Complex 1 can be selectively inhibited by ____ and ____.
How so?
rotenone & amytal
Stops e- transfer from NADH in mitochondrial matrix, but NOT from succinate DH or glycerol P shuttle
34
T/F rotenone & amytal stops e- transfer from NADH in matrix, along with succinate DH and glycerol P shuttle.
FALSE; it is from NADH, but **NOT** from succinate DH **or** glycerol P shuttle
35
Rotation of the 𝜸 subunit distorts___. this changes ...?
⍺ and β subunits
changes binding affinity for ADP + Pi and ATP
36
Movement of 𝜸 subunits causes ⍺β subunits to have ___ distinct conformations. These are...?
O= nonbinding sites⇒ ejection of ATP
L= loose binding site⇒ADP + Pi binds
T= tight binding site⇒ ATP generated and transfered to O ( ADP + Pi go to T)
ADP + Pi ☞ Kd ≈ 10⁻⁵ M
ATP ≈ 10⁻¹² M
37
Walk me through the process of this 𝛾 rotation
✯ 𝛾-subunit again rotates 120° powered by 3H+
✯ 3H+ per active site make 1 ATp
✯ 3 active sites bc ⍺/β dimers need to bind
✯ 9H+ to run all 3 active sites
9H⁺
↓
3 x 120° (or 360°) movements
↓
1 revolution
↓
3 (ADP+ Pi→ ATP)
38
Where exactly is the ATP synthase pump located?
Inner membrane of the mitochondria
39
What do uncouplers do exactly?
Drain H+ gradient without making ATP → heat
40
what is the role of 2,4- Dinitrophenol (DNP)?
It acts as an uncoupler in cellular respiration. It disrupts the proton gradient across the mitochondrial membrane by allowing protons to flow back into the mitochondrial matrix without producing ATP. This "drains" the H+ gradient, which typically powers ATP synthesis, and instead releases the energy as heat. This has been used as a **weight loss** tool, as it inc. metabolic rate, but it can be dangerous due to its impact on energy efficiency and heat production in cells.
41
Humans have multiple UCP. name and give descriptions of them
**UCP1**
*Keeps babies (and adults) warm
* Brown fat → heat
* Knock out mice are cold sensitive
**UCP2**
* Broadly expressed (including brain)
* Proposed to protect neurons against free-radical induced death
**UCP3**
* Expressed in muscle
* Over-expression → lean mice
42
T/F, only babies have brown fat; we dissolve it as we get older
FALSE; adult humans DO have brown fat. it is just more in young and lean than old and fat
43
What antiporters does the malate/aspartate shuttle require to functoin?
⍺-KG and Glu/Asp
44
What molecule enters the mitochondria in the malate-aspartate shuttle, and what exits as a balance?
Malate (2e-) enters the mitochondria, and (𝛼-KG) exits to maintain balance across the mitochondrial membrane
45
Where is the malate-aspartate shuttle primarily located?
A:
In the inner mitochondrial membrane, where it facilitates the transfer of reducing equivalents (NADH) from the cytosol into the mitochondria for ATP production.
46
Which molecule exits the mitochondria in the malate-aspartate shuttle, and what molecule enters as a counterpart?
Aspartate exits the mitochondria, while glutamate enters to keep the cycle in balance.
47
What is the primary purpose of the malate-aspartate shuttle?
To transfer reducing equivalents from NADH in the cytosol into the mitochondria for ATP synthesis without directly moving NADH across the mitochondrial membrane.
48
Explain how the ATP synthase pump works
❇︎**Location and Purpose:** The ATP synthase pump is located in the inner membrane of the mitochondria. Its main job is to make ATP, the energy "currency" of the cell.
❇︎**Proton Gradient:** The electron transport chain, which is right before ATP synthase in the process of cellular respiration, pumps protons (H⁺ ions) from the mitochondrial matrix to the intermembrane space, creating a high concentration of protons outside.
❇︎**Flow of Protons:** These protons naturally want to flow back into the matrix where their concentration is lower, and ATP synthase is like a gate that lets them back in. The protons move from the intermembrane space into the matrix through a channel in ATP synthase.
**How Movement Drives ATP Synthesis:**
☞As protons flow through ATP synthase, they cause part of the enzyme to rotate—specifically, the c-ring and the gamma subunit (central stalk). Think of it like turning a *crank!*
☞This rotation pushes and changes the shape of another part of ATP synthase where ADP and Pi (inorganic phosphate) are waiting. The change in shape squeezes ADP and Pi together to form ATP.
**Stable vs. Rotating Parts:**
The rotating part is the c-ring and the gamma subunit.
The stable part, which doesn't move, is the F 1 complex (where ATP is actually made) and the stator that holds it in place.
49
What is moving and what is stationary in the ATP synthase pump
☞The "head" (**F1 complex**, which includes the alpha and beta subunits where ATP is produced) stays *stationary*.
☞The "stalk" (central gamma subunit and the c-ring in the F 0 part) does rotate.
50
What direction of the protons flowing in the ATP synthase pump?
✯Protons (H⁺ ) move from the **intermembrane space into the mitochondrial matrix**. This movement follows the proton gradient created by the electron transport chain, which pumps protons into the intermembrane space, building a high concentration of protons outside the inner mitochondrial membrane.
As protons flow down their gradient through the F0 subunit of ATP synthase, they cause the c-ring and attached gamma subunit to rotate. This rotation drives conformational changes in the F1 subunit, where ADP and inorganic phosphate (Pi) are combined to form ATP.
51
How is fat turned into heat (step format)
✦ Fat
→ acetyl-coA
→NADH, FADH₂
→ H⁺ gradient
→ drain via UCP
➜ **HEAT**
52
write anti-oxidant mechanisms
**Super-oxide dismutase**
2 O2-* + 2H+ → H2O2 + O2
Amyotrophic lateral sclerosis (ALS, Lou Gehrig)
**Catalase**
2 H2O2 → 2 H2O + O2
**Glutathione peroxidase**
2 GSH + R-O-O-H → GSSG + ROH + H2O
(GSSG + **NADPH** → 2 GSH + NADP+)
recall discussion of people with
↓G6PDH activity (Ch 15, pentose-P)
* Se, Vit E, Vit C, uric acid
53
Where do light reactions occur?
In chloroplasts
54
instead of H+ being pumped across the inner membrane as in mitochondria, where are these protons being pumped in light reactions?
into (inside) THYLAKOID COMPARTMENT
55
what structure does Chlorophyll resemble?
Heme, but contains **Mg** rather than Fe
56
T/F respiration used NAD and FAD whereas photosynthesis used NADP
TRUE!!
57
T/F allows plants to produce more energy from blue light than red light
FALSE! even though blue energy is higher, chlorophyll absorbs it the same way
58
What molecules absorb light energy, transferring it btwn molecules until it reaches the rxn center?
✪ antenna chlorophylls bound to protein
✪ carotenous
59
What type of reaction centers do purple photosynthetic have?
Simple, well-characterized rxn centers similar to mitochondrial **complex III**
60
How do purple photosynthetic bacteria utilize red light in photosynthesis?
Red light excites electrons in the special pair, leading to rapid charge separation and electron transfer through bacteriopheophytin.
61
What role does bacteriopheophytin (Bpheo) play in purple photosynthetic bacteria?
Bpheo temporarily traps excited electrons in an unstable state, facilitating proton pumping across the membrane.
62
How do purple photosynthetic bacteria generate ATP?
They create a proton gradient through electron transport, which drives ATP synthase, similar to mitochondrial ATP production.
63
Why can’t purple photosynthetic bacteria easily produce NADPH?
They lack a direct pathway to make NADPH, unlike higher plants, which can use light energy to produce both ATP and NADPH.
64
How many protons does Cytochrome bc1 complex pump to cytochrome 2 in purple photos. gradient?
4H+
65
Higher plants can use light to make both___AND___
ATP; NADPH
2 rxn centers e- from H2O→NAD**P**H
66
Where does the Z scheme start?
The scheme starts at **Photosystem II** (PSII).
67
What is the role of PSII in the Z scheme?
PSII absorbs light energy, exciting electrons that are then passed through an electron transport chain.
68
What molecule helps transfer electrons from PSII to PSI?
Plastoquinone (Q) and **plastocyanin**.
69
What is produced as electrons move from PSII to PSI?
ATP is produced along this part of the electron transport chain.
70
What happens to electrons at PSI in the Z scheme?
They are re-excited by light and transferred to ferredoxin, contributing to NADPH formation.
71
How are electrons lost from PSII replaced?
Electrons are replaced by the splitting of water (photolysis), which also releases oxygen.
72
Which of the following has the most negative standard reduction potential (highest energy e-)?
a)NADPH
b) FADH2
c) QH2
d) reduced form of ferredoxin
d) reduced form of ferredoxin
73
What is the difference btwn Plastocyanin and Ferrodoxin?
**Plastocyanin:**
❇︎*Location:* Found in the thylakoid lumen.
❇︎*Role: *Plastocyanin transfers electrons from the cytochrome b6f complex (part of the electron transport chain) to Photosystem I (PSI).
❇︎*Significance:*This transfer is critical because it allows electrons initially energized by Photosystem II (PSII) to reach PSI for further excitation. Plastocyanin effectively "bridges" PSII and PSI, allowing continuous electron flow.
**Ferredoxin:**
❇︎*Location:* Located in the stroma, near PSI.
❇︎*Role:* Ferredoxin accepts high-energy electrons from PSI after they have been re-excited by light.
❇︎*Significance:* It is the final electron acceptor before NADP⁺ is reduced to form NADPH. Ferredoxin transfers electrons to the enzyme ferredoxin-NADP⁺ reductase (FNR), which catalyzes the production of NADPH, a vital molecule used in the Calvin cycle.
74
Plastiquinone resembles...
Ubiquinone
75
Why must PS1 & PSII be kept apart?
to prevent a short circuit
(P700→ P680)
76
How many protons do you pump out of Cytochrome b6f?
8H+
77
PSII transfers electrons in batches of __. Why?
4; to prevent free radicals from forming. Avoids dangerous intermediates like O₂⁻, H₂O₂, *OH
78
We get O2 at flash __ and __ rather than__ and ___. why's that
O2 at flash **3** and **7** instead of 4 and 8 bc there is already O2 present in the system
79
List the differences btwn PS1 and PSII
✦PSI is in unstacked lamellae (tubes so can travel)
– feeds NADPH into C fixation
✦PSII is in stacked lamellae
– isolates H20→O2 from matrix
- dangerous bc it was rip H2O molec. apart
80
Are Plastiquinone and Plastocyanin mobile or mobile in the photosystems
they are mobile and move e- btwn complexes (PSI; PSII)
**Cytb₆f is uniformly distributed
81
If PSI is limiting...
If PSII is limiting...
If PSI is limiting
↑ QH₂ ↓ Q
→ more LHC to PSI
(move antennae comlex here to balance out)
If PSII is limiting
↓QH₂ ↑Q
→ more LHC to PSII
(move antennae comlex here to balance out)
LHC= light harvesting complex; which is mobile
82
How much energy is lost as light moves btwn antenna complexes?
Almost no energy
83
List the differences in H⁺ movement in mitochondria vs chloroplasts
**Mitochondria**
✦ H⁺ pumped from mito. matrix out into intermembrane space
✦→ both a proton and a charge gradient (charge more important)
**Chloroplasts**
✦ H⁺ pumped from matrix into lumen of thylakoid compartment
✦ proton gradient only
84
How can plants afford to throw away the most important part of its charge gradient? how?
Light already has so much energy, they have all the energy they need
Movement of Mg⁺² cancels charge gradient (used to regulate photosynthesis)
85
T/F dark reactions occur during the day for regular plants but at night for dessertic plants
FALSE; dark reactions ONLY occur the day and do not directly require light
86
Draw the Calvin cycle
lec 6 of slide 65
87
All but two Calvin cycle intermediates are also found in gluconeogenesis or pentose P pathway. These are...?
✸ Ribulose-1,5-phosphate (RuBP)
✸Sedoheptulose1,7-bisphosphate (SBP)
88
Where do we see aldolase in the Calvin cycle?
Erythrose 4-P→ Sedoheptulose 1,7-bisP
89
Is Sedoheptulose bisphosphatase a reversible or irreversible enzyme?
Irreversible
90
The over-expression of sedoheptulose-1,7 bisphosphatase (SBPase) can...?
Increase the photosynthetic rate of plants
➲ tobacco plants
91
Rubisco
RuBP + CO2 → 2(3PG)
➥ also makes 2-phosphoglycolate
✿ Large subunits encoded by nucleus
– Contains active site
✿Small subunit encoded by chloroplasts
*✿Accounts for ≈50% of leaf protein
– Kcat ≈ 3/sec (↑ Km)
– **Very inefficient**
92
Rubisco has 2 enzymatic steps:
✿ **Carboxylase**: RuBP + Co₂ →2 (3PG)
➥ fixes CO2 into organic molecules
➥ Km CO2= 9um
✿**Oxygenase**: RuBP + O2 → 3PG + 2-phosphoglycolate
➥ fixes O2, leading to photorespiration, which is INEFFICIENT
➥ Km O2=250 uM
➥
93
RuBP carboxylase is inhibited by___ during___
CA1P; night
(a transition state analog)
94
The pumping of H+ into ___ of thylakoid space will do what exactly to the pH of the matrix of the mitochondria? what else occurs
inside; ↑↑
Mg⁺² comes out to balance the charge, which turns on RuBisco
95
What happens when the sun shines on the plants?
Ferredoxin goes from oxidized→reduced→ (NADPH)
↓
Thioredoxin goes from its oxidized to reduced form...which reduces thiol (conformation change)
96
Reduction of Ferredoxin/Thioredoxin by PSI activates/ inactivates
**Activation** (the ones needed for calvin cycle)
❤︎ Phosphoribulokinase (→RuBP)
❤︎ SBPase (→ sedoheptulose-7P)
❤︎GA3P DH
❤︎F1,6Pase
**Inactivate** ( don't want glycolysis)
✘ PFK-1
97
Most fixed carbon is exported from chloroplast by the____
Pi/triose antiporter
98
What are the two types of starches?
1.**Amylopectin**
➥very large *branched* glucose polymer
➥ ⍺-1,4 & ⍺-1,6 bonds
➥ complex structure
2.**Amylose**
➥long *linear* chains of glucos
➥ ⍺-1,4 bonds
* 25% amylose→ firm non-sticky rice
*15% amylose→ soft sticky rice
99
What do we need to put into the mitochondria whenever we take a triose phosphate out?
PO4, or else mitochondria runs out of phosphorus ( makes triose phosphate which can make Gluc + Fruc
100
Write UDP-Glucose mechanism
Lec 6, slide 49 & 50
101
___fills empty spaces in amylopectin structure
Amylose
102
The synthesis of starch has a different high energy glucose donor. This is…?
ADP-G rather than UDP-G
Different structure
103
Why is it bad that RuBisco makes 2-phosphoglycolate?
Bc it can't keep going into Calvin Cycle, which then goes to chloroplast→peroxisome→mitochondria (which can reduce this thru C4 metabolism)
104
What troublesome side reaction does Rubisco perform?
Rubisco can use O₂ instead of CO₂, leading to the production of 3PG and **2-phosphoglycolate**, an inefficient byproduct that must be processed through photorespiration.
105
Photorespiration (the release of CO2) mechanism in Mitochondria
2 Gly→ Ser + ⤳CO2 + ↝ NH3
106
Why is Rubisco’s oxygenase reaction inefficient?
The oxygenase reaction produces 2-phosphoglycolate, which requires energy-intensive processing through photorespiration, consuming energy without producing ATP or sugars.
107
Why can Rubisco bind both CO₂ and O₂?
Rubisco’s active site is designed to fit CO₂, but due to its small, linear structure, O₂ can also fit into the same binding site, causing an unwanted oxygenase reaction.
108
Affinity for Rubisco ⬇︎ as temperature___
⬇︎photorespiration by___ local CO2 conc.
⬆︎
⬆︎
109
What is the primary function of C4 metabolism?
How so?
help increase ⇧ photosynthetic efficiency by reducing ⇩ photorespiration
Initially fixes CO2 in *mesophyll cells*, creating a higher CO2 conc. in bundle sheath cells, which reduces the interaction of Rubisco with O2
110
In which types of plants is C4 metabolism commonly found?
More common in tropical plants where high temperatures inc⇧ rate of photorespiration
111
What enzymes are involved in C4 metabolism.
What type of rxn is this?
**Mesophyll cell**
☞Carbonic Anhydrase
☞PEP Carboxylase
☞Malate Dehydrogenase
**Bundle-sheath cell**
☞Malic Enzyme (NADPH)
**Anaplerotic**
112
How is C4 metabolism discriminatory?
C4 metabolism is “discriminatory” because it uses the enzyme PEP carboxylase to selectively bind CO2 in the form of bicarbonate, avoiding O2 interference. This selectivity minimizes the production of 2-phosphoglycolate, which would otherwise result from photorespiration and reduce photosynthetic efficiency.
113
Some desert plants limit water loss by....?
opening stomata to let in CO2 at night
114
What are the rxns of a desert plant in day vs night?
**Night**
starch→ PEP + CO2 → ↑↑ malate
(open stomata, suck up CO2)
**Day**
malate → pyruvate + CO2
CO2 → Calvin cycle → starch (original + more)
(stomata closes)
115
what type of "C" is Maize vs Rice?
Maize: C4
RIce: C3
116
90% of dietary lipid is___
Triacylglycerol (TAG)
117
TAG=
✬ 16:0
✬ 18:0
✬18:1
✬18:2
✬20:4
glycerol + fatty acids
✬16:0- palmitic
✬18:0- stearic
✬18:1- oleic
✬18:2- linoleic
✬20:4- arachidonic☞ eicosanoids (prostaglandins etc.)
118
double bonds are ___ is natural
cis
119
120
Initial substrate: dietary fat (TAGs)
Final product: TAGs
Pathway:
Bile forms micelles around fat molecules
Intestinal lipases (TAG → FA + glycerol)
Fatty acids enter intestinal epithelial cells (requires bile and FA binding protein)
Chylomicron assembly (fat ball (cholesterol + TAG) with ApoC-II)
Chylomicrons → lymph system → blood
Chylomicrons (ice cream truck) adheres to capillary beds of muscle and adipose tissue
ApoC-II (speaker) activates extracellular lipoprotein lipase
Unload TAG → FA + glycerol
FA enters cells
Will be oxidized or stored
Chylomicron remnants (incl. cholesterol) go back to liver
121
In the first step of fat intake, Fat particles →
thru…
micelles (microscopic)
thru Bile (acts as a detergent)
122
Bile
Bile acts as a detergent
– Cholesterol derivatives
– Synth in liver
– Stored in gall bladder
123
Lipid digestion step-by-step breakdown
1. Formation of Micelles:
* Fat particles are broken down into micelles with the help of bile.
* Key Point: Bile acts as a detergent, made from cholesterol derivatives, synthesized in the liver, and stored in the gall bladder.
2. Action of Intestinal Lipases:
* Intestinal lipases break down triglycerides (TAG) into free fatty acids (FA) and glycerol.
* Key Point: Some lipases have a “lid” that opens to reveal a hydrophobic active site, allowing the breakdown of lipids.
3. Uptake of Fatty Acids by Intestinal Epithelium:
* Fatty acids enter the intestinal epithelium, requiring bile and a fatty acid-binding protein that helps lipid transport in the aqueous environment.
4. Assembly into Chylomicrons:
* Inside the intestinal epithelium, fatty acids and glycerol reassemble into triglycerides. Cholesterol and apolipoproteins are added, forming chylomicrons.
5. Chylomicron Transport:
* Chylomicrons move through lymph and blood. In muscle and adipose tissue capillaries, they adhere to binding sites, and ApoC-II activates lipoprotein lipase, unloading triglycerides for breakdown.
6. Cellular Uptake and Metabolism of Fatty Acids:
* Fatty acids enter cells for either energy production through β-oxidation or storage by reassembling into triglycerides.
7. Chylomicron Remnants Process:
* After triglycerides are unloaded, cholesterol-enriched chylomicron remnants travel to the liver, delivering dietary cholesterol and recycling cholesterol from bile.
124
What role does bile play in lipid digestion?
Bile acts as a detergent, helping to break down fat particles into micelles. It is synthesized in the liver, derived from cholesterol, and stored in the gall bladder.
125
What is the function of intestinal lipases in lipid digestion?
Intestinal lipases break down triglycerides (TAG) into free fatty acids (FA) and glycerol, with some lipases exposing a hydrophobic active site for this purpose.
126
Why is a fatty acid-binding protein needed in the intestinal epithelium?
It allows fatty acids to move through aqueous environments without merging with cell membranes, aiding in their transport within cells.
127
Describe the assembly process of chylomicrons.
Fatty acids and glycerol reassemble into triglycerides in the intestinal epithelium, combined with dietary cholesterol, bile cholesterol, and apolipoproteins to form chylomicrons.
128
How do chylomicrons deliver triglycerides to cells?
Chylomicrons attach to capillary binding sites in muscle and adipose tissue, where ApoC-II activates lipoprotein lipase to unload triglycerides for breakdown into fatty acids and glycerol.
129
What happens to fatty acids after they enter cells?
Fatty acids are either oxidized for energy through β-oxidation or stored as triglycerides, linking carbohydrate and lipid metabolism.
130
What is the fate of chylomicron remnants after triglycerides are removed?
Cholesterol-enriched chylomicron remnants are taken up by the liver, delivering dietary cholesterol and returning cholesterol from bile to the liver.
131
Glycerol portion of FA goes to___
what happens there?
liver
▸Glycerol→3P-Glycerol
▸3P-Glycerol (NOT adipo + FAD → DHAP + FADH₂
▸ DHAP → glucose
132
Acyl-Coa synthetase mechanism
FA + CoA + ATP⟷ FA-CoA + AMP + PPi (reversible)
133
lipid oxidation occurs in___
lipid synthesis occurs in___
THEREFORE, need way to ensure that
❁ FA to be oxidized →
❁ FA for lipid synth →✘
inside mitochondria
cytoplasm
mitochondria x2
134
VitaminB12 contains
Cobalt ( heme-like ring)
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B12 deficiency
* Synthesized by certain bacteria in gut
– Not by plants or animals
* Intrinsic factor binds B12 and allows absorption
* Humans need ≈ 3 µg/day
– Usually store 3-5 year supply in liver
* Insufficient B12 → pernicious anemia
* ↓ red cells & hemoglobin → ↓ neurological function
Often fatal in elderly
* Usually insufficient intrinsic factor
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