Metabolism Flashcards
(118 cards)
1
Q
“Summarise the reaction by which amino acids are joined together. ”
A
lecture 1
2
Q
“Differentiate between the different types of bond that combine to stabilise a particular protein conformation. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
l 1
3
Q
“Sketch a trimeric peptide, identifying the amino -terminus, carboxyl terminus and side chains. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
L1
4
Q
“Distinguish between an α-helix and a ß-pleated sheet and appreciate the bonds that stabilise their formation”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
L1
5
Q
“Summarise the concepts of primary structure, secondary structure, tertiary structure and quaternary structure with respect to proteins. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
L1
6
Q
Amino acids are formed from proteins in what type of reaction
A
L1 q
7
Q
Label the structure below
A
L 1 q
8
Q
L1 quizes in 100 seconds
A
9
Q
explain the concept of free energy, how changes in free energy can be used to predict the outcome of a reaction and how ATP is used as a carrier of free energy to drive energetically unfavourable reactions
A
L2
10
Q
“Explain how ATP acts as a carrier of free energy and is used to drive energetically unfavourable reactions. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
11
Q
xplain how enzymes act as catalysts of reactions. Draw graphs to show the effects of substrate concentration, temperature and pH on reactions catalysed by enzymes.
A
L2
12
Q
“Define the role of the coenzyme NAD in the reaction catalysed by lactate dehydrogenase.”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
l2
13
Q
“Explain how enzymes act as catalysts of reactions with reference to the reactions catalysed by lysozyme and glucose-6-phosphatase. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
L2
14
Q
“Distinguish between lock and key and induced fit models of substrate-enzyme interactions. ”
A
L2
15
Q
“Sketch a cartoon of the three stages of cellular metabolism that convert food to waste products in higher organisms, illustrating the cellular location of each stage. ”
A
16
Q
“Explain the metabolism of glucose by the process of glycolysis, recalling the key reactions, in particular those reactions that consume ATP and those that generate ATP. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
pg 427-429 Essential biology book
17
Q
What is substrate-level phos[phorylation, and distinguish between this and oxidative phosphorylation
A
pg 71 ibook
18
Q
“Distinguish between the aerobic and anaerobic metabolism of glucose with reference to the enzymes involved and the comparative efficiencies of each pathway with respect to ATP generation.”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
(met 3 slide 24)“Pyruvate generated in glycolysis has three possible fates including alcoholic fermentation (yeasts) and the generation of lactate under the control of the enzyme lactate dehydrogenase.
This process is anaerobic and is characteristic of mammalian muscle during intense activity when oxygen is a limiting factor. It allows NAD+ to be regenerated and thus glycolysis to continue, in conditions of oxygen deprivation. i.e. conditions in which the rate of NADH formation by glycolysis is greater than its rate of oxidation by the respiratory chain. NAD+, you recall, is needed for the dehydrogenation of glyceraldehyde 3-phosphate, which is the first step in generating ATP for the body (Lecture 2).
”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
19
Q
“Summarise the reactions catalysed by lactate dehydrogenase and creatine kinase and explain the diagnostic relevance of their appearance in plasma.
”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
Met 3 , slide 24-30
20
Q
“Explain the oxidative decarboxylation reaction catalysed by pyruvate dehydrogenase, with reference to the product and the five co-enzymes required by this enzyme complex. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
meth 3 34 -38
“The third fate of pyruvate generated from glycolysis is the generation of acetyl CoA which occurs in the mitochondria of cells.
Pyruvate + CoA + NAD+ → acetyl CoA + CO2 + NADH
The acetyl CoA thus formed is committed to entry into the citric acid cycle and can ultimately produce ATP by the process of oxidative phosphorylation (lecture 5).
The reaction is catalysed by the pyruvate dehydrogenase complex which consists of three individual enzymes and also five co-factors. Some of these co-factors are a permanent part of the enzyme complex and are known as prosthetic groups
e.g. Pyruvate Decarboxylase has the prosthetic group thiamine pyrophosphate (TPP) and Dihydrolipoyl Dehydrogenase has the prosthetic group FAD (Flavine Adenine Dinucleotide)
“Overall, the enzyme has five steps:
(i) Decarboxylation of pyruvate to give hydroxyethyl TPP
(ii) Oxidation & transfer of hydroxyethyl TPP to lipoamide to give acetylipoamide
(iii) Transfer of the acetyl group to CoA to give acetyl CoA
(iv) Regeneration of oxidised lipoamide generating FADH2
(v) Regeneration of oxidised FAD, generating NADH”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
21
Q
met 3 quiz
A
22
Q
“Explain the Krebs or TCA (tricarboxylic acid) cycle with particular reference to the steps involved in the oxidation of acetyl Co-A and the formation of NADH and FADH2 and the cellular location of these reactions. ”
A
pg 75 ibook
23
Q
Describe the location of the enzymes involved in the krebs cycle, and where they act
A
“The Krebs cycle enzymes are soluble proteins located in the mitochondrial matrix space, except for succinate dehydrogenase, which is an integral membrane protein that is firmly attached to the inner surface of the inner mitochondrial membrane. Here, it can communicate directly with components in the respiratory chain.
”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
24
Q
“Summarise the glycerol phosphate shuttle and the malate-aspartate shuttle, in particular stating why these mechanisms are required. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
A
pg 76( right), pg 77(left), met 4 slide 28-31
25
“Perform calculations to calculate the theoretical maximum yield of ATP per glucose molecule due to the krebs cycle during aerobic respiration. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
“The majority of the energy that derives from the metabolism of food is generated when the reduced coenzymes are re-oxidised by the respiratory chain in the mitochondrial inner membrane in a process known as oxidative phosphorylation (lecture 5).
The Krebs cycle only operates under aerobic conditions, as the NAD+ and FAD needed are only re-generated via the transfer of electrons to O2 during oxidative phosphorylation.
ibook pg 75 :Re-oxidation of the reduced co-factors NADH and FADH2 by the process of oxidative phosphorylation yields the following:
Three ATP molecules are formed by the re-oxidation of each NADH molecule.
Two ATP molecules are formed by the re-oxidation of each FADH2 molecule.
Therefore, from the Krebs Cycle:
1 X acetyl CoA gives 3 x NADH plus 1 x FADH2 + 1x GTP = 12 ATP
”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
26
Where does the malate aspartate shuttle primarily take place as oppose to glycerol-phosphate
met 4 slide 27
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
27
“Recall two examples of the use of NADPH in reductive biosynthesis.”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
“biosynthesis of RNA and cholesterol, allowing electron transport in catabolism to be kept separate to that of anabolism.
”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
28
Explain th e difference between NADP and NAD and its advantage
“NADP+ is a relative of NAD+, differing only by a phosphate group attached to one of the ribose rings. The phosphate group does not participate in electron transfer, but gives it a slightly different conformation, meaning that it will bind to different enzymes than NAD+. NADP+ takes part in anabolic reactions, whereas NAD+ takes place in catabolic reaction”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
29
pg 78 ibook quiz
30
Describe structural feature s thta allow acetyl CoA to donate acetyl to other molecules
Met 4 slide 7
31
Summarise the process by which amino acids lead to products that can enter the TCA cycle
Met 4 slide 24-26
32
“Summarise the processes by which the amino acid alanine is converted into acetyl-CoA.”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
33
“
Draw a cross sectional representation of a mitochondrion, identifying its component parts. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
pg 79
34
“Explain the proposed evolutionary origins of mitochondria. and outline the evidence for them
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
pg 80 ibook left side
35
Describe the size of mtDNA and its abundance in the cell
“Human mitochondrial DNA (mtDNA) existing as a 16,569 bp circular genome, encoding just 37 genes. However, unlike nuclear DNA, several copies of the mitochondrial genome can be found within a single cell.
”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
36
Exemplify the importance of mtDNA , and the importance of the mother when it come to the exemplified importance
“Despite its diminutive size, the importance of mtDNA is highlighted by the fact that mutations within mtDNA are frequent cause of human genetic disease.
The inheritance of mtDNA is via the ovum , meaning that mtDNA mutations are transmitted to all maternal offspring. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
37
Using change in free energy describe how the two relevant coenzymes in the respiratory chain can bee responsible for several phosphanhydride bonds(for deeper understanding try and understand why the mnumbers shown do not work out)
pg 81 ibook left side up till (_Chemiosmotic Model of Oxidative Phosphorylation_)
38
Summarise the electron transport chain in mitochondria with reference to the functions of coenzyme Q (ubiquinone) and cytochrome c.
pg 81 . ibook right side Each unit in the chain has a HIGHER AFFINITY for electrons than the previous unit, allowing them to flow in a logical order.
pg 68 Laz's notes(Redox reactions
**Redox Reactions**
Electron transfer reactions involving a **reduced substrate** and an **oxidised substrate**..A substrate that can exist in both oxidised and reduced states is known as a **redox couple** e.g. NAD+/NADH, FAD/FADH2.The ability of a redox couple to accept or donate electrons is known as the **reduction potential** or **redox potential**.
**Standard Redox Potentials**
**NEGATIVE** **redox potential = tendency to** **DONATE**
**POSITIVE** **redox potential = tendency to** **ACCEPT**
Each successive membrane complex or carrier has a **more positive redox potential** than the previous component of the ETC. This means that the transfer of electrons from one complex to the next is **energetically favourable**. As they progress along the chain, the electrons **lose energy**.
39
# Define the chemiosmotic theory.
(pg 81 ibook )“Chemiosmotic Model of Oxidative Phosphorylation
Oxidative Phosphorylation proceeds in two steps:
1) The translocation or movement of protons from within the matrix of the mitochondria. This is controlled by the electron transport or respiratory chain.
2) The pumped protons are allowed back into the mitochondria through a specific channel, which is coupled to an enzyme which can synthesise ATP (ATP synthase). See Alberts, Figure 14-2, page 455 for a nice analogy of the theory with a battery operated pump. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
40
“Explain how ATP synthase is able to generate and utilise ATP respectively, with reference to its structure.”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks. x
“2) The pumped protons are allowed back into the mitochondria through a specific channel, which is coupled to an enzyme which can synthesise ATP (ATP synthase). See Alberts, Figure 14-2, page 455 for a nice analogy of the theory with a battery operated pump. ” pg 81(chemiosmotic model of oxidative phophorylation)
41
What is special about proline as an amino acid
* When proline is joined to a polypeptide chain - **the NH group of the amino acid is LOST**
* This prevents the side chain from hydrogen bonding with C=O groups of another residue within the helix
* This distorts the helical conformation
* Puts a **kink** into it
pg 43 (LAz)
42
Describe how proteins forl in general and what can interfer with this and how
* (pg 43 (Folding of Proteins))
* Proteins generally fold into the single conformation of **lowest energy**
* Chaperones may be involved to make sure that folding occurs in the **most energetically favourable way**
* By breaking bonds that hold the protein together, we can denature the protein into the original flexible polypeptide
* Common Denaturants used in the lab:
* **Urea** (breaks hydrogen bonds)
* **2-mercaptoethanol** (breaks disulphide bonds)( (
43
Explaoin how warfarin works
* pg 43 (Post Translational modification of proteins)
* The starting set of 20 amino acids can be modified to create novel amino acids, enhancing the capabilities of the protein.
![]()
* The formation of g-carboxyglutamate residues within several proteins of the blood clotting cascade (e.g. factor IX) is critical for their normal function by increasing their calcium binding capacities.
* **WARFARIN works by inhibiting the carboxylation reaction**
44
Describe the role of cytochrome oxidase
pg 67 (Cytrochrome oxidase) Laz's notes)
## Footnote
**Cytochrome Oxidase**
Cytochrome Oxidase is the last membrane complex in the electron transport chain. It initially receives **2 electrons** from cytochrome C in the first cycle of the electron transport chain, and then the cycle repeats so that cytochrome oxidase has **4 electrons** in total.
Cytochrome oxidase passes the electrons to **Oxygen** to generate **water**.
Furthermore, **4 protons** are pumped into the intermembrane space, thus enhancing the proton gradient.
4e- + 4H+ + O2 --------------\> 2H2O
Oxygen is the ideal terminal electron acceptor because it has a **high affinity for electrons**, proving a driving force for oxidative phosphorylation.
45
“Explain how ATP synthase is able to generate and utilise ATP respectively, with reference to its structure.”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
pg 29 ABS" notes
46
Why does FADH2 pump lead to one less proton being oump in the respiratory chain
[pg 82 below ATP synthase diagram]
## Footnote
“Succinate dehydrogenase is an integral membrane protein that is firmly attached to the inner surface of the inner mitochondrial membrane. There, it can communicate directly with ubiquinone.
“Succinate dehydrogenase is an integral membrane protein that is firmly attached to the inner surface of the inner mitochondrial membrane. There, it can communicate directly with ubiquinone. ”
47
Suggest how mitochondrial respiration may be examined experimentally.
pg 83 ibook
48
Met 5 quizzes, pg 84 ibook
49
“Recall the chemical composition of unsaturated and saturated fatty acids. and describe their storage in mammals
pg 85 ibook
“Fatty acids (FA) are composed of a hydrophobic carbon chain and a hydrophilic head group and can be saturated with hydrogens (saturated fatty acids) or unsaturated (with one or more double bonds). They are typically stored as triacylgycerol (TAG) species. Double bonds introduce kinks into the carbon chains of thee molecules and means that they pack less tightly together, and are generally liquid at room temperature. In contrast, saturated fatty acids pack tightly together and are generally solid at room temperature.”
“In mammals, fatty acids are stored as tryglycerides in the cytoplasm of specialised cells known as adipocytes. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
50
Recall the posible deivations of fats , and the processes that follow digestion up till their storage
i(book pg 85 2nd paragraoh & pg 86 left side line 1-3)“
Fats are derived from three primary sources, namely the diet, de novo synthesis by the liver and release from storage depots in adipocytes. Lipid digestion by the action of lingual gastric and pancreatic lipase results in the formation of Monoacylglycerol (MAG), diacylglycerol (DAG) and free FAs. During digestion, bile salts are released from the gall bladder and help to solublize fatty acids molecules, forming micelles which include other molecules such as cholesterol, lysophosphatidic and fat-soluble vitamins e.g. A, D, E and K. Fatty acids from the micelles are absorbed by enterocytes lining the brush border of the small . intestine and TAGs are resynthesized under the control of several enzymes prior to incorporation into chylomicrons (CM) and transportation (covered in lecture 7). ”
51
Describe a cause of a lack of bile salts and the possible consequences of this lack
pg 86 line 3 up till beta-oxidation
“If bile salts are lacking (e.g. obstruction of the bile duct by a gallstone) then fat may pass through the gut undigested resulting in steatorrhea (fatty stool). Steatorrhea is also a major side effect of Orlistat/lipstatin usage, which prescribed as an obesity treatment and is an inhibitor of gastric and pancreatic lipases. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
52
summarise the pathways for the metabolism of fatty acids with respect to the substrates and products, coenzymes used, carrier molecules and their cellular locations
firstly, for information on the first enzyme in the cycle: (pg 88 ibook ,left side(Disorders of fatty acid metabolism) then read from pg 86 (β-oxidation ) to pg 87, ibook,
script for info on first enzyme :
“A family of 5 different Acyl-CoA-dehydrogenases catalyze the initial step in each cycle of fatty acid β-oxidation within the mitochondria matrix:
Each Acyl-CoA-dehydrogenase can bind a fatty acid chain of varying lengths:
3-hydroxyacyl-coenzyme A dehydrogenase
Short-chain acyl-coenzyme A dehydrogenase
Medium-chain acyl-coenzyme A dehydrogenase
Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase
Very long-chain acyl-coenzyme A dehydrogenase ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
53
What is the role of the thioester linkage in acetyl CoA
pg 75 laz's notes (Process of beta oxidation)
54
Describe how ketone bodies are formed in metabolism(this requires some other deeper understqanding which i did not have)
pg 75 Laz's notes(**Ketone Body Formation)**
**KEY POINT: Acetyl CoA formed from b****-oxidation can only enter the TCA cycle if****b****-oxidation and carbohydrate metabolism are balanced****. This is because OXALOACETATE is needed for entry of Acetyl CoA into the TCA cycle.**
If fat breakdown predominates (e.g. when fasting/starving), **acetyl CoA forms:**
* **Acetoacetate**
* **D-3-hydroxybutyrate**
* **Acetone**
* **These are known as KETONE BODIES.**
*
55
Calaculate the ATP yield of palmitate
pg 75(**Net ATP Production of Palmitate b-oxidation compared to aerobic respiration:) to page 76 (Fatty acid biosynthesis) Laz's note**
56
summarise the pathways for the synthesis of fatty acids with respect to the substrates and products, coenzymes used, carrier molecules and their cellular locations
pg 76(**Fatty Acid Biosynthesis - Lipogenesis) to 77 Laz's notes**
57
explain how inborn errors of fatty acid metabolism may cause disease, and how thus diseases are managed
pg 88 left side(Disorders of Fatty acid Metabolism) to 89 ibook
58
Met 6 quiz on pg 89
59
Where is cholesterol mainly found, and what is its functions there
“More than 90% of the body’s cholesterol (shown below) is found in cell membranes where it can increases or decreases membrane stiffness, depending on temperature and nature of membrane (see Cells Lecture 1).”
60
What are the orignins of cholesterol
“Although some is taken up in the diet, the majority of the body’s cholesterol is synthesized by the liver from the molecule acetyl-CoA. ”
Excerpt From: Imperial College London. “MBBS Year 1 MCD Autumn 17/18.” iBooks.
61
summarise the synthesis of cholesterol from acetyl-CoA(long shit)
Laz's notes pg 85-88
62
Describe the three principle stages of the synthesis of cholesterol from acetyl CoA and describe where rhey occur
pg 85 (Cholesterol biosynthesis - the numbered bulltet point part) Laz's notes
The biosynthesis of cholesterol can be split into **three main parts**:
1. Synthesis of **isopentyl pyrophosphate**, an activated isoprene unit which serves as a key building block (occurs in cytoplasm).
2. Condensation of **six molecules of isopentyl pyrophosphate** to form **squalene** (occurs in cytoplasm).
3. Cyclisation and demethylation of squalene by **monooxygenases** to give cholesterol (occurs in ER).
63
Describe the synthesis of isopentyl pyrophosphate and describe where it occurs
occurs in the cytoplasm, pg 85(**Biosynthesis of Cholesterol - Step by Step ) to pg 86 Laz's notes**
64
Describe the formation of squalene from isopently pyrophosphate
pg 87 Laz's notes
65
Describe how cholesterol is made from squalene
pg 88 Laz's notes
66
he synthesis of bile acids and steroid hormones from cholesterol
pg 89 Laz's notes
67
Decsribe how bile salts function
1st section on Laz's notes pg 90
68
Explain the genral mechanism of storage of cholesterol in cholesterol transport , including descriptions of structure
pg 92 ibook(Lipid Transport)
69
Name the different types of Lipoproteins, and describe how they are recognised by different cells
pg 91 from (**LIPOPROTEINS ARE CATEGORISED ACCORDING TO THEIR DENSITY:) to (Lipoprotein Lipase)** Laz's notes
70
Describe how fats are transported in the body, adnd taken up by tissues to be used.
pg 91 (Lipoproteins) Laz's notes
71
Describe the difference in function between LDL and HDL and where pathologies may occur
pg 93 ibook (paragraph 3)
72
Describe the cause and consequences of Familial Hypercholesterolaemia, and describe different sevgerities of this and under which circumstances one may get such severities
pg 92 writing bit Laz's notes
73
Describe the features of the different classes of Familial Hypercholesterolaemia(kind of extra)
table on pg 93 Laz's notes
74
Describe the medication that may be used to manage FH
pg 94
75
Label the following molecule
pg 90 Laz's notes
76
WHich molecule is this
HDL
77
metabolism quiz on pg 94 ibook
78
Name and exemplify the three types of intracellular transport
**(pg 78Types of Intracellular Transport) Laz's notes**
1. **Gated Transport** - e.g. nuclear import
2. **Trans-membrane Transport** - e.g. import of newly synthesised proteins into ER
3. **Vesicular Transport** - e.g. inter-organellar transport
79
Descrinbe the structure of the golgi appratus and its function, include details of how it functions in an overviewexcytosis
pg 79(Vesicular transport complexity) Laz's notes
**Vesicular Transport Complexity**
* The Golgi Apparatus is responsible for packaging and sending the proteins from the ER.
* The Golgi Apparatus has three sections: **cis**, **medial** and **trans**
* The **cis** Golgi network is **closest to the ER**.
* Exocytosis Overview:
* Endoplasmic Reticulum --\> Cis Golgi network
* Cis Golgi Network --\> Medial Golgi Apparatus --\> Trans Golgi Network
* Trans Golgi Network --\> Cell Surface via different types of secretory vesicle
80
(1)Give an overview of endocytosis
pg 79 Laz's notes : **Endocytosis Overview:**
**Endocytosis Overview:**
* Material recognised at plasma membrane is brought in via endocytic pathway
* First pathway is the **Early Endosome** (involved in **recycling**) - material from early endosome can recycle back to the plasma membrane and keep going round and round.
* Or it can be sorted into another compartment called the **Late Endosome**.
* If the material is **destined for destruction** it will be taken to the **lysosome** to be broken down.
81
Describe the secretory or exocytotic pathway
pg 80(**The Secretory or Exocytic Pathway)** Laz's notes
82
Recall what happens in the ER for post translational modification and quality control
pg 80(**ER: Post-Translational Modifications and Quality Control)**
83
`Explain diseases that can occur as result of problems with post translational modification and quality control in the ER
pg 81 (**Cystic Fibrosis Transmembrane-Conductance Regulator (CFTR))**
**Cystic Fibrosis Transmembrane-Conductance Regulator (CFTR)**
* CFTR is an **ABC transporter-class chloride channel** in epithelial cell plasma membranes.
* Mutations of the CFTR gene affects the functioning of the chloride channels in the membrane which causes Cystic Fibrosis.
* The **most common mutation (****Δ****F508)** results from **DELETION** of **three nucleotides**, which causes the **loss of phenylalanine (Phe)** at the 508th position on the protein.
* As a result, the CFTR does not fold properly and is degraded in the ER.
* Small molecule corrector 407882 binds to the cytoplasmic domain of ΔF508 CFTR and enhances its movement to the cell surface, restoring function.
84
Describe the fucntions of glycocylation and explain compartment identity
pg 83 Laz's notes top parts
**Functions of Glycosylation**
* Folding
* Protection (e.g. glycocalyx)
* Receptors
* Recognition (e.g. blood groups)
**Compartment Identity**
* All the different membrane-bound intracellular compartments have a distinct protein and lipid content. Proteins make sure that they get to the correct compartment by having:
* Targeting/Sorting signals (e.g. lysosomes)
* Retention signals
* Retrieval signals
85
Decribe the post-translational modification of proteins that occurs in the golgi apparatus, and give an example of this (include detials of the golgi apparatus structure in your answer)
pg 82 Laz's notes
86
87
Describe how sorting occurs at the trans golgi network
pg 83 Laz's notes (Sorting at the trans golgi network)
**Sorting at the Trans Golgi Network (Exocytosis)**
* Proteins have gone through the Golgi Apparatus and had their carbohydrates processed.
* RECAP: **Two Most Common Routes: Constitutive Secretory Pathway + Regulated Secretory Pathway**
* Constitutive Secretory Pathway - continually going out towards the plasma membrane in an **unregulated** manner.
* Regulated Secretory Pathway - for materials that have to be secreted in a **regulated** manner e.g. neurotransmitter. Proteins, such as neurotransmitter, will be sorted into a specific secretory vesicle and the vesicle is **stored in the cytoplasm** until its release is **triggered** by a **SIGNAL** e.g. hormone.
* When the signal molecule (e.g. hormone) binds to the **cell surface receptor** it triggers an **intracellular signalling pathways** that causes the **release of the stored secretory proteins**.
88
Describe all the post-translational modification that a lysosymal enzyme goes through as it moves through the golgi Apparatus, and how it is funall sorted.
pg 84 **Laz's notes**
* Specific example of how carbohydrates are important in certain types of sorting events - Lysosomal Enzymes.
* These enzymes are involved in degrading proteins and lipids and they are destined to go to the **lysosome**.
* **Lysosomal hydrolase precursors** are recognised in the **cis Golgi network**.
* The carbohydrates on the Lysosomal hydrolase precursor are modified by the **addition of a phosphate** **onto the carbohydrate, which acts as a TAG**.
* **The phosphorylation of mannose is catalysed by** **PHOSPHOTRANSFERASE****.** (using ATP as the phosphate donor)
* Now the lysosomal enzymes are tagged with a **phosphorylated sugar** - a very specific tag.
* When they reach the **trans Golgi network**, the phosphorylated sugar is detected by a very specific receptor - **Manose-6-Phosphate receptor** - which leads to the enzymes being packaged into specific vesicles.
* The specific vesicles have **targeting signals** on the outside which are specific to the **lysosome** but the vesicles travel first to the **late endosome**.
* The late endosome contains a **proton pump**, which **pumps protons** from the cytoplasm **into the late endosome** so **THE LUMEN OF THE LATE ENDOSOME IS RELATIVELY ACIDIC**.
* In the **acidic environment** the M6P receptor releases the phosphorylated lysosomal hydrolases.
* Once released, the **phosphate is removed** by a **phosphohydrolase** - SO IT CAN NO LONGER GO BACK TO THE GOLGI BECAUSE IT DOES NOT HAVE IT'S PHOSPHATE.
* Because of this mechanism, you get an **accumulation of lysosomal hydrolases in the late endosome**.
* **THE LATE ENDOSOME MATURES TO FORM A LYSOSOME.**
The M6P receptors are **recycled** back to the trans Golgi network
89
Describe the different types of endocytosis
pg 85 Laz's notes (ENdocytosis)
* **Receptor-mediated endocytosis** - substances bind to specific receptors and begins to form a vesicle which has a protein coat around it.
* **Pinocytosis** - fluid drinking - the cell extends it's membrane and takes in some extracellular fluid.
* **Macropinocytosis/Phagocytosis** - can take up large particles such as bacteria.
90
Describe the precess of endocytosis ,including details of the possible fates of endocytosed material
pg 85(Fate of endocytosed material)
**Fate of Endocytosed Material**
* The first place endocytosed material goes in the **early endosome** - the **sorting compartment**. From here, there are three things that could happen:
1. **Recycling** - the material could be recycled and sent back to the plasma membrane. E.g. Transferrin receptor (the main mechanism for taking up iron) is recycled back to the plasma membrane.
2. **Degradation** - see below
**Transcytosis** - material can be carried to the **basolateral membrane**
91
Give an illustration of the degradatio pathways with your own example
pg 85 Laz's notes (**lustration of Degradation Pathway:** EXAMPLE - LDLs)
92
93
Recall how proteins are synthsised initially
pg 96 ibook(Free and membrane bound ribosomes )
94
Recall the different metabolic functions in different tissues
pg 103 ibook and pg 104 NB
95
Provide a summary of glycolysis and the processes that could ensue s under different conditions in metabolism
pg 97 laz's notes(**Summary of Glycolysis:), which continues a little on pg 98**
96
Define metabolism
The sum of all processes in the body.
97
Provide a summary of glycolysis and what ensues under different conditions in metabolism
98
List the measures of metabolism
Oxygen Uptake, Carbon Dioxide Production, Heat Generation
99
100
For the muscle , brain and nervous system, adipose tissue , heart and liver identify:
proportion of body weight
any relevent informattion on how it uses ATP
a description where relevant on its use of fats and vcarbohydrates
pg 96 Laz's notes (**General Metabolic Features of some specialised tissues:)**
101
Describe the process of gluconeogenesis
pg 98 Laz's notes
102
Summarise protein and fat metabolism in the body,
pg 99 Laz's notes
103
Exaplin aerobic and anaerobic repiration during exercise, includean explaination of the hormones involved
pg 100 Laz's notes
104
Describe possible feeatures of a glucose metabolism step that metabolic control ussually takes place at
pg 101 Laz's notes AD
105
Describe the controllers of the glucose metabolism pathway
Laz's notes pg 101 AD
The pathway is controlled by:
* **Product** of the reaction or pathways (the product could be an activator or inhibitor of the enzyme)
* External **signalling molecules** relaying information from other pathways
* **Hormones**
106
Give the details of a step of glucose metabolsim where it 's control is dependent on enzyme activity
Laz's notes pg 101 AD
107
Describe the functions of four different hormones that tak epart in the hormonal control of metabolism
pg 102 Laz's notes
* **Insulin** - secreted when glucose levels rise - stimulates uptake and use of glucose and storage of glycogen and fat
* **Glucagon** - secreted when glucose levels fall - stimulates gluconeogenesis and the breakdown of glycogen and fat
* **Adrenaline** - strong and fast metabolic effects to **mobilise glucose** for 'fight or flight'
* **Glucocorticoids** - steroid hormones that increase synthesis of metabolic enzymes concerned with **glucose availability**.
108
DIffertiate between type q and type 2 diabetes
* Type I - cannot make insulin
* Type II - reduced responsiveness to insulin
109
What is the genreal effect on metabolism of defective insulin signalling
* The general effect on metabolism of defective insulin signalling is that your metabolic status is controlled **'*as if you were starving***'. Without the insulin signalling, your body doesn't know that you have fuel.
110
Reccal compliations of diabetess
* COMPLICATIONS:
* Hyperglycaemia - causing progressive tissue damage
* Increase in plasma fatty acids and lipoproteins - possible cardiovascular complications
* Increase in ketone bodies - possible acidosis
* Hypoglycaemia - possible coma if insulin dosage is not correctly controlled
111
How is metabolism affected by diabetes across the body
Laz's notes pg 103(**How metabolism is affected)**
112
Describe Regulation of hormone secretion in pancreatic b cells
Laz's notes pg 103(Regulation of hormone secretion in pancreatic b cells)
113
Describe the function of GLP 1
Laz's notes pg 104
114
Describe what happens across metabolism normally after a meal, in terms of hormonal and enzymatic control
Laz's notes pg 104 where i decided to underline
115
What is the role of glucagon in diabetes
**Diabetes is not just a result of a decreased sensitivity to insulin or insulin deficiency but it's also a defect in terms of glucagon secretion.**
**Glucagon in Type 2 Diabetes**
* Important protection against hypoglycaemia.
* Major Site of Action - LIVER - glucagon stimulates gluconeogenesis and glycogenolysis.
116
Describe the **Regulation of glucagon secretion in pancreatic** **a** **cells:**
Laz's notes pg 105 (**Regulation of glucagon secretion in pancreatic** **a** **cells:)**
117
Describe the changes iacross metabolism after a meal and after prolonged fasting,include a descrption of hormones involved in this also
pg 106 Laz's notes
118
Met 9 quiz pg 105 ibook
