Solving Biology 9700 AS Winter 25 Paper 22 (Theory) | O/N 25 QP22

Added: 2026-05-12

[00:00:02]Okay.

[00:00:03]So, the paper I plan to do today is winter 2025 paper two variant two.

[00:00:12]So, the wall of the small intestine is highly folded to form villi.

[00:00:18]Between the villi and infoldings between the villi are infoldings known as crypts of Lieberkühn. So, over here we see infoldings. They are basically known as the crypt of Lieberkühn.

[00:00:32]Figure 1.1 is a diagram of a section through a single villus and a crypt of Lieberkühn.

[00:00:42]Figure 1.1 shows that the epithelial Sorry. Figure 1.1 shows that the epithelium of the villus contains mainly goblet cells and cells known as enterocytes. So, the epithelium basically consists of enterocytes.

[00:00:59]And it consists of goblet cells.

[00:01:04]Both cell types have microvilli on the apical surface. Apical surface is the surface facing the gut lumen. So, yeah, my bus gut lumen is so it's money surface go. This is the apical surface and on the apical surface of all the enterocytes and goblet cells there are microvilli present.

[00:01:28]Goblet cells are involved in the production of mucus.

[00:01:32]Enterocytes are adapted for the absorption of the soluble product of digestion. These products enter the circulatory system.

[00:01:41]A student incorrectly stated that an enterocyte has many cilia on its apical surface. Explain the difference between a cilium and a microvillus. So, a cilium is basically made made up of micro tubules which are arranged in a 9 + 2 arrangement, whereas microvillus, they're microvilli, they're made up of actin filaments. So, that's the difference.

[00:02:08]Yeah.

[00:02:09]So, cilium is made from microtubules, which are organized in a 9 + 2 arrangement.

[00:02:41]Microvillus is made up of actin filaments.

[00:02:57]Okay. So, just one role of the mucus produced by the goblet cells of the villus. So, my bus we get the angel hominy apical surface here.

[00:03:05]That apical surface uh basically has uh mucus lining on it, right? My bus to make you so that mucus is basically a thick fluid. I'm doing bus getting here mucus key in the epithelium of the small intestine to hominy bus getting here.

[00:03:28]It basically is there to trap pathogen if any pathogen has entered through um the food that we are consuming. So, it's good job getting here. Yeah, but hominy bus getting here to mucus here. It's a fluid, right? So, what we can get in here, it basically reduces a friction or any weird and tear to get friction you better have to hold here. So, it basically reduces a friction when food particles are moving through the guard.

[00:03:52]So, my personal guard may be anywhere be mucus or that food particles are solid particles and they're obviously brushing against the walls of the guard. So my best candidate is possible to get mucus ready or that to my best possible that friction or that to move get out the my love um food particles solid particles through the guard. So the mucus has a role of even reducing friction when solid particles are digestive material is moving through the guard.

[00:04:26]So we can say perhaps pathogens or other way alternative we can say to alternative could be reduces friction for the movement of digestive substance.

[00:05:01]In figure 1.1 blood vessel X delivers blood to the capillary network. If it is delivering the blood to the capillary network then it had definitely has to be oxygenated blood.

[00:05:12]Where tissue fluid is formed some of the fluid passes back into the capillaries and then into the venule blood vessel X receives blood from an artery. So blood vessel X is receiving blood from the artery and it is delivering the blood to the capillary.

[00:05:30]Name the type of blood vessel represented by X. So X would be an arteriole because arterioles are the connecting bridges between the artery and the capillary. Um I know that they have mentioned that the blood vessel X receives blood from an artery. So it is a blood vessel which is not an artery Instead, it is receiving blood from an artery, and it is delivering the blood to the capillary network. So, the blood vessel between the artery and capillary, or the connecting bridge between the artery and the capillary, is the arteriole.

[00:06:02]Describe the formation of tissue fluid in the capillary network of the villi.

[00:06:06]So, basically, blood enters the arterial end of the capillary at a high hydrostatic pressure, and thus, the components the small components of the blood, such as glucose, amino acids, are filtered out of the blood with the blood plasma through the fenestrations. Fenestrations are basically the gaps or the pores in the endothelial walls of the capillary.

[00:07:28]In response to the presence of compounds in the gut lumen, enteroendocrine cells synthesize and release peptides, short chains of amino acids that are cell signaling molecules.

[00:07:41]One of these cell molecule is known as GLP-1. GLP-1 initiates a number of responses in different body cells. Some of these responses include the increase in release of the hormone insulin from the cells of the pancreas, the decrease in release of acid from cells in the stomach. Outline in sequence the main stages involved in the process of cell signaling by GLP-1.

[00:08:05]Now, we have to get the cell signaling, ma'am. Basically, there are three stages. One stage is basically the production of the cell signaling molecule from the target cell from the side of origination or the side of production.

[00:08:19]Side of production my first care my first side of production enteroendocrine cells are So, the GLP-1 is produced and secreted by the entero- endocrine cells.

[00:08:59]It travels via the bloodstream to the target cell, which would have a receptor complementary to what GLP-1 The GLP-1 would bind to the receptor and trigger a sequence of responses within the target cell.

[00:10:09]So, we have to talk about the movement of the cell signaling molecule via the bloodstream, its movement towards the target cell, and its binding with the complementary receptor to gain our three marks.

[00:10:24]Paneth cells, which are secretory cells, are located between intestinal stem cells at the base of the crypt of Lieberkühn, as shown in figure 1.1.

[00:10:36]Figure 1.1 A Paneth cell has a very different appearance to an intestinal stem cell. Figure 1.2 is a transmission electron micrograph of a Paneth cell.

[00:10:45]So, this is basically our Paneth cell.

[00:10:50]Surrounded with obviously intestinal stem cells. So, it's the surrounding with intestinal stem cells and all in between of our Paneth cell here.

[00:10:58]Paneth cells are formed following the mitotic division of an intestinal stem cell during a cell cycle. Complete the cell cycle shown in figure 1.3 by naming in sequence the stages of mitosis. This sequence is P mat, which is prophase, metaphase, anaphase, and telophase.

[00:11:27]One of the functions of a Paneth cell is to synthesize and secrete peptides and proteins that act against pathogens in the gut lumen.

[00:11:38]State and explain the evidence visible in figure 1.2 which suggests that a pendant cell is a secretory cell and synthesizes many peptides and proteins.

[00:11:48]Now, if it is a secretory cell what evidence do we have in the figure to tell us that a pendant cell is a secretory cell?

[00:11:56]A secretory cell is basically a cell which uh transports substances, which form substances and then transports those substances outside of the cell.

[00:12:08]And obviously, our best substances as bulk transport move out here. So, bulk transport may exocytosis would have.

[00:12:15]Over here, we can see how many solid vesicles are here.

[00:12:20]1 2 3 4 and so on and so forth. I mean, sorry.

[00:12:24]Vesicles of different sizes are there here.

[00:12:28]Now, I must be getting there.

[00:12:30]The presence of many vesicles confirms that this is a secretory cell and these vesicles would basically fuse with the cell membrane and release their contents outside of the cell via exocytosis. So, the secretory cell only got my password evidence here.

[00:12:47]Well, presence of a lot of secretory vesicles are.

[00:12:52]I don't know the second evidence longer here. Okay, how can we say looking at this particular cell that it is involved in the synthesis of peptides and proteins? If we look closely can you see how many rough endoplasmic reticulum are there? I could write this one here.

[00:13:10]On the endoplasmic reticulum, so the presence of RER a lot of RER or an abundance of RER within the cell suggests that this cell is involved in the secretion of peptides and proteins. Then I make a good day here. Mitochondria will be there and this is a mitochondria. This is a mitochondria.

[00:13:34]Yeah, don't know if you have my best mitochondria. Yeah, they are The presence of mitochondria protein synthesis is essentially an active process. It requires ADP. So many mitochondria within the cell suggest that they are um actively playing a role in synthesizing ADP which is needed in the protein synthesis process.

[00:13:59]Okay.

[00:14:04]There are many secretory vesicles within the paneth cell suggesting that they contain substances which will be secreted outside of the cell via exocytosis.

[00:15:01]The paneth cell has an abundance of rough endoplasmic reticulum.

[00:15:30]which is responsible for protein synthesis.

[00:15:51]Mitochondria are also present for ATP synthesis.

[00:16:08]Which is needed during protein synthesis.

[00:16:22]So, one mark for presence of secretory vesicles, one mark for the presence of rough endoplasmic reticulum, and another mark for mitochondria.

[00:16:31]Explain why Paneth cell has a very different appearance to an intestinal stem cell. Obviously, an intestinal stem cell can differentiate into any cell type. It can differentiate into an enterocyte, into a goblet cell. So, you can see intestinal cell may stem cell differentiate right?

[00:16:51]Um because initially it was undifferentiated. So, yeah, you can also use the word of specialized. So, specialized or differentiated or use it.

[00:16:59]We would say that Paneth cell is differentiated or it is specialized compared to a stem cell which is undifferentiated or it is unspecialized.

[00:17:10]So, Paneth cell Let's move towards to the next question.

[00:17:20]Cholera is an infectious intestinal disease caused by a bacterial pathogen.

[00:17:25]Name the species of bacterium that causes cholera. So, that is Vibrio cholerae.

[00:17:35]The World Health Organization WHO recommends a number of different approaches for the prevention and control of cholera.

[00:17:43]Two of these are Authorities should provide access to safe drinking water.

[00:17:47]Individuals and communities should practice preventive personal hygiene.

[00:17:51]Suggest and explain how these two approaches help in the prevention and control of cholera. Now, cholera is transmitted through the fecal-oral route.

[00:18:01]If we are drinking contaminated water, it is likely that we ingest the cholera bacterium and therefore drinking safe water would prevent the entry or the ingestion of Vibrio cholerae within our system.

[00:18:17]To practice preventive personal hygiene basically means that every time uh we are using the washroom, we end up washing our hands to ensure that any feces is not present on our hands. And if feces are not present on our hands, they would not contaminate food or water through which the transmission chain of cholera would be propagated.

[00:18:48]So, cholera spreads via fecal-oral route and is present in contaminated water.

[00:19:12]Drinking clean and safe water.

[00:19:22]Would ensure that cholera patch bacterium causing cholera is not ingested.

[00:19:52]Practicing preventative personal hygiene include frequent washing of hands especially after using the toilet to ensure that the feces are not present on the water.

[00:20:53]water.

[00:21:04]Mass vaccination is Mass vaccination Mass vaccination using an oral cholera vaccine can be carried out in situation where there is a high risk of people developing the disease.

[00:21:18]Passive immunization involves transferring antibodies into a person for the prevention or treatment of an infectious disease.

[00:21:26]Some of the infectious diseases for which passive immunization is available use monoclonal antibody. Passive immunization for cholera using monoclonal antibody could be available in the future. Complete table 2.1 to compare an oral cholera vaccine and passive immunization for cholera. Fill in the empty box in row one. Circle the correct answers from the choices given in rows three, four, and five.

[00:21:50]Okay, so in an oral cholera vaccine, the component causing the desired response is an antigen or we can say an attenuated pathogen.

[00:22:03]Attenuated pathogen is basically the pathogen in its weakened form from which we remove the disease-causing ability.

[00:22:11]Now, when we look at rows three, four, and five, stimulates production of memory lymphocytes. Now, because there is an antigen which is being injected in the body, there would be the stimulation of B cells which would differentiate into plasma cells and memory cells.

[00:22:28]In passive immunization, because there is no antigen being injected in the body, there would no there would be no immune response and thus there would be no production of memory lymphocytes.

[00:22:39]Length of time we need to have an effect. Obviously, we vaccine get through when we inject a pathogen in the bloodstream, it takes a time for the antibodies and the memory cells to form because first we have a we have an innate immune response which is basically phagocytosis and then we move towards the adaptive immune response which includes your humoral immune response, if you call the antibody-mediated immune response. So, it takes longer.

[00:23:09]However, because we're directly injecting antibodies in the passive immunization, it would take a shorter time for the response to be produced.

[00:23:18]Duration of immunity, a vaccination gives you a long-term immunity, so it gives you longer immunity. Whereas, the duration of immunity when we're just injecting antibodies, it is shorter because eventually the antibodies would move or would break down.

[00:23:40]The production of monoclonal antibodies for treatment involves the formation of hybridoma cells from two different cell types. Name the two types of cell that fuse to form a hybridoma cell and explain why this fusion is necessary.

[00:23:52]So, how am I supposed to get get to them?

[00:23:55]We fuse the myeloma cells, which are cancerous obese cells, with the Myeloma cells are fused with plasma cells.

[00:24:07]And why is this needed?

[00:24:10]It is needed uh because uh plasma cells cannot divide via mitosis, whereas myeloma cells can divide via mitosis.

[00:24:19]Um plasma cells can produce the desired antibodies.

[00:24:24]So, plasma cells can produce the desired antibodies.

[00:24:39]However, they cannot divide my via mitosis.

[00:25:01]>> Myeloma cells can divide by mitosis.

[00:25:12]Therefore, fusing them together forms a hybridoma cell, which can divide and produce desired antibody.

[00:25:44]Now, let's move towards question number five.

[00:25:50]A plant is described as a mesophyte.

[00:25:54]A plant that is described as a mesophyte has evolved to grow in conditions that do not normally experience water stress.

[00:26:01]So, my bad. Mesophytes basically as a plant with the head to grow garden conditions where the hopper water availability what do you have access to water present with that?

[00:26:12]They do not experience water stress or low availability of water basically.

[00:26:16]Figure 5.1 is a diagram of a cross-section of the leaf of a herbaceous dicotyledonous mesophyte.

[00:26:21]Complete Figure 5.1 by naming structure A and the tissue layer B. So, the structure A is basically a layer above the upper epidermis. So, that is the layer of cuticle.

[00:26:32]It's the home for back seat cuticle in the last day and cuticle in the last day.

[00:26:37]B is basically a layer of spongy mesophyll cells. B in my past would I go?

[00:26:44]Spongy mesophyll cells.

[00:26:51]Okay. They're basically asking us to the tissue layer, not the cell. So, spongy mesophyll tissue. You can get all spongy mesophyll cells.

[00:27:00]In xerophytes, xerophytes are plants adapted to live in water stress.

[00:27:14]In xerophytes, some of the structural features shown in figure 5.1 are modified as adaptations for surviving of conditions of water stress. Complete table 5.1 to show how the structural features The structural feature listed may be modified in the leaf of a xerophyte.

[00:27:32]Each feature feature should have a different example of a modification structure name.

[00:27:36]Waxy cuticle. How is a waxy cuticle different in a xerophyte?

[00:27:48]Would it be the same or would it be different?

[00:27:52]And if different, then how?

[00:27:54]Yeah, exactly. So, waxy cuticle is thicker to prevent water loss through upper epidermis.

[00:28:18]Mesophytes have a single layer On the other hand, a multi-layered epidermis has two or three layers of the upper epidermis cells. So, so that water loss through the upper surface easily now.

[00:28:42]Multi-layered upper epidermis.

[00:28:52]Who do what epidermis? Do what epidermis for my bus viewers tomato or they have you have a bus sunken a tomato or they have trichomes present or they have some crazy adaptation like they get fewer stomata.

[00:29:10]Okay, so we have done three questions question one, two, and five yesterday.

[00:29:15]We do three, four, and six today.

[00:29:20]The gene LCT codes for the enzyme lactase.

[00:29:27]In babies, lactase synthesis is necessary for digesting lactose, the sugar found in milk. So, lactase is needed for lactose digestion.

[00:29:39]Another gene, MCM6, has introns that have a regulatory role in the expression of gene LCT.

[00:29:49]A regulatory role in the expression of gene LCT basically means that they basically control the amount of times regulate the amount of times the gene LCT would be expressed. So, they're basically regulating the transcription of the LCT gene.

[00:30:07]Gene MCM6 codes for a protein that has no involvement in lactase synthesis.

[00:30:14]As children got older, the MCM6 introns are responsible for a decrease in lactase synthesis.

[00:30:25]So, with age, the MCM6 introns are responsible for a decrease in lactase synthesis. This decrease in lactase synthesis is also known as lactase non-persistence.

[00:30:39]LCT and MCM6 are located on the same chromosomes in humans.

[00:30:47]Suggest differences between gene LCT and gene MCM6 other than their locations and different positions on the same chromosome. Obviously, if there are two different genes, the sequence of nucleotides would be different. Okay, other sequence of nucleotide would have been the same.

[00:31:04]They would have been the same genes, not different. So, sequence of nucleotides of gene LCT and gene MCM6 would be different. Then, it is also possible the length, which means how many nucleotides make up a single gene, would be different. So, how many base pairs do they have?

[00:31:42]Different lengths the two genes would have different lengths.

[00:32:02]Now, we know that LCT codes for an enzyme. So, we can say that the enzyme LCT is coding for an enzyme, whereas MCM6 is coding for the different protein.

[00:32:16]So, LCT gene codes for an enzyme lactase, whereas the MC M6 codes for a different protein product.

[00:32:52]With reference to the process of lactate synthesis, explain the relationship between a transcribed strand and a primary transcript, a primary transcript and a messenger RNA. So, we have to tell how transcribed strand and a primary transcript are related and then we have to explain how a primary transcript and mRNA are related. So, my bus DNA care those strands of them. We have two strands of the DNA.

[00:33:20]In transcription, only one of the two strands is used, which is known as the transcribed strand.

[00:33:30]From the transcribed strand, we form the primary transcript.

[00:33:35]So, my bus transcribed strand, this is our transcribed strand, this is our primary transcript.

[00:33:42]So, the transcribed strand is transcribed, but it undergoes transcription for a complementary primary transcript to be formed. Now, this primary transcript has both the introns and the exons. The introns from the primary transcript has to be removed where the process of splicing so that an mRNA can be formed.

[00:34:05]So, my bus primary transcript splicing about your modification about eventually mRNA one time.

[00:34:13]So, transcribed strand is transcribed to form a primary transcript, a a complementary primary transcript, whereas the primary transcript undergoes post-transcriptional modification, which involves splicing of the introns to form mRNA. So, we'll write that down.

[00:34:32]The transcribed strand is the DNA strand which undergoes transcription to form a complementary primary transcript.

[00:35:14]The primary transcript undergoes post-transcriptional modification in which introns are removed via splicing to form mRNA.

[00:35:57]Clear? Any questions so far?

[00:36:01]A mutation in a regulatory intron of MCM6 allows lactase synthesis to continue.

[00:36:11]This is known as lactase persistence. In this mutation, the number of nucleotides in the intron remains the same, but one of the nucleotides is different to the original nucleotide. State the type of mutation that is the cause of lactase persistence. So what I've seen that mutations of DNA base addition base deletion base substitution I mean base addition or base deletion would be the number of nucleotides wouldn't have been the same.

[00:36:39]It would have either increased in the case of base addition or the number of nucleotides would have decreased in the case of base deletion.

[00:36:47]If the number of nucleotides is same but a nucleotide has has replaced an original nucleotide in that case base substitution has taken place.

[00:37:03]Figure 3.1 summarizes the reaction catalyzed by lactase. Draw the ring structure of alpha glucose in the box provided to complete figure 3.1. So AB alpha which means the OH on the first carbon would be below.

[00:37:34]Some people with lactase non-persistence may be lactose intolerant.

[00:37:39]They may have symptoms such as abdominal pain if their diet contains lactose.

[00:37:44]Lactase supplements tablets can be taken before milk or milk based products are consumed to avoid symptoms of lactose intolerance.

[00:37:54]A student compared the activity of two different concentrations of a lactase supplement using an artificial substrate ONPG instead of lactose.

[00:38:05]A solution of ONPG is colorless but the hydrolysis of ONPG by lactase releases a colored product.

[00:38:14]So my best substrate is colorless.

[00:38:19]But after hydrolysis the product is colored.

[00:38:28]Now, to see how different concentration of a lactase supplement, which helps with lactose digestion, how does that work?

[00:38:41]So that we can see how fast the digestion or how fast the hydrolysis is in two different concentration of a supplement.

[00:38:52]Colorimeter I'm using this. Okay. The student plan to follow the progress of the reaction for each concentration of lactase using a colorimeter. Are you aware of how a colorimeter works, Anna?

[00:39:04]Or should I explain the basics of colorimeter?

[00:39:14]I'll show you how a colorimeter looks like.

[00:39:19]Yeah, it's the one used in the practicals.

[00:39:25]It also comes up some P1 and P2. So, let me show you how it works.

[00:39:37]Give me a second. Let me picture copy paste kar leti hu.

[00:39:42]So, this is basically how a colorimeter looks like.

[00:39:47]Achha.

[00:39:48]So, Hamare pass hota kya hai? Hamare pass you can see um Ye basically hamare pass different test tube hoti hai. At a given time I'm usually a test tube placed here. Can you see how a test tube placed there?

[00:40:04]I will try to zoom in over here. Can you see a test tube is placed in this space?

[00:40:11]So, what happens is in a colorimeter space provided in which we have to place test tube. We place it like that.

[00:40:18]Hamare pass hota kya hai? Hamare pass we green light will pass through our Now, how many of us have green light pass?

[00:40:33]Obviously solution So, how many of us have light must test tube will cross really?

[00:40:42]Some amount of light will be absorbed by the substances present within the solution.

[00:40:48]light So, how many of us have basically absorbed and get a transmittance How many of us us have absorbed over the course of the reaction change we have?

[00:41:01]How many of us have transmitted over the reaction change we have? Usually the color emitter values that have absorbed and data How many of us have a solution amount of light absorbed color? How many of us have darker solution only in the other absorbed only?

[00:41:17]How many of us have clear or lighter solution only in the other absorbed only? It's going to simply explain and understand that if I have a glass of water and a glass of Coca-Cola and if I have light exposed to both of the glasses and we see the clear water and all of the light pass through the car windows and the car windows >> [snorts] >> our car windows clear and transparent If you have tinted windows So, if the solution is not clear the solution contents light absorb the transmitted or partly Does that make sense?

[00:42:39]The student plan to follow the progress of the reaction for each concentration of lactase using colorimeter. Explain why the student chose to use a colorimeter to follow the progress of the reaction for each concentration of lactase for my bus exact quantitative values are the end.

[00:42:53]Um colorimeter key reading color change eyes errors are the whole I got him a colorimeter use key in case that would eliminate human error to my bus accurate results I engage while using a colorimeter.

[00:43:15]So through a colorimeter quantitative results are obtained.

[00:43:50]Reducing human judgement errors if the student would have simply obtained conclusions by observing the change in color.

[00:44:30]The lactose in milk can be hydrolyzed using immobilized lact ase or by using lact ase free insulation.

[00:44:45]Lact ase This results in milk and milk products that do not contain lactose and so are suitable for lact ase intolerant I would have milk made lact ase beads added to the milk make a getting a free lact ase added to the milk made lact ase free milk and the lact ase present.

[00:45:07]The beads or the free lact ase would hydrolyze it resulting in a lact ase free milk or a lact ase free milk products to be formed which then in [snorts] turn are suitable for the use of lact ase intolerant people. So we have lact ase free milk and now we have lact ase free milk but that is made up of lact ase hydrolysis after that.

[00:45:29]Scientists carried out an investigation to compare the activity of lact ase immobilized in very small magnetic beads known as magnetic micro spheres with free lact ase at different temperatures and at different pH values. Figure 3.2 shows the activity of immobilized lact ase and the activity of free lact ase at five different temperatures. Figure 3.3 shows the activity of immobilized lact ase and the activity of free lact ase at eight different pH values. So we have the pH and we have the activity at different temperatures and we have the activity which we have observed here.

[00:46:01]Now I'm telling you said that he had activity of the lactase enzyme at it is better than the free lactase.

[00:46:14]The my pass higher yield of hydrolysis produced already.

[00:46:21]One advantage of using magnetic microspheres with immobilized lactase is that they can be easily recovered using an electric field and reuse. So I'm immobilized lactase the advantage of using that is that we can easily reuse it because I'm using a recollect using a magnet. With reference to figure 3.2 and figure 3.3, explain why the results indicate that there are other advantages in using immobilized lactase instead of free lactase to produce lactose free product. So we can clearly see the my pass the immobilized lactase the immobilized lactase has an overall greater yield compared to the free lactase and different pH as well as at different temperatures. We can also see that our immobilized enzyme is thermostable. Even at higher temperatures, its percentage activity is better than the free lactase.

[00:47:23]Then my pass if you look at temperature, so at a range of different pH sorry if you look at the pH at a range of different pH it is still giving us a higher activity compared to the free lactase. So my pass the free lactase at the free lactase is giving us high activities in these pH which is pH 6.5, pH 7, pH 7.5 and pH 8. But my pass even pH 9 but your lactase immobilized lactase the activity it is comparatively Bacteria can be classified according to the type of cell wall they have. Gram-negative bacteria have a cell wall with an outer layer known as the outer membrane.

[00:48:09]Gram-positive bacteria do not have an outer membrane, but have a much thicker peptidoglycan layer than Gram-negative bacteria. Figure 4.1 is a diagram of a section through the cell wall of a Gram-negative bacterium, which has an outer layer.

[00:48:25]With reference to Figure 4.1, outline the similarities and differences between the outer membrane of a Gram-negative bacterial cell and the cell surface membrane of a eukaryotic cell. This is basically the outer membrane of your Gram-negative bacteria.

[00:48:44]So, similarities can I similarities you have that we have phospholipids present.

[00:48:50]I might have phospholipids present there. So, like a eukaryotic cell membrane, phospholipids are present.

[00:48:59]Then, we have membrane proteins present. So, like a eukaryotic membrane, I might have us membrane proteins present and you can have a money similarities over there.

[00:49:13]Differences can I differences you have lipopolysaccharide is present in the outer membrane, which we do not see in eukaryotic cell membrane.

[00:49:22]Furthermore, I might have us get get in here only mono layer present here phospholipids here I might have us eukaryotic cell membrane um a phospholipid bilayer present over here. So, I might have us mono layer by difference here.

[00:49:36]I might have >> by lipid present okay. So we have a monolayer difference here.

[00:49:57]And we have what do you call it lipo polysaccharide difference when we compare the outer membrane of the gram-negative bacteria to a eukaryotic cell membrane.

[00:50:09]So similarities.

[00:50:17]Both have phospholipid molecule.

[00:50:31]And transport protein.

[00:50:42]Differences would be eukaryotic cell membrane does not have lipopolysaccharides.

[00:51:12]And it has a phospholipid bilayer instead of a monolayer.

[00:51:41]Pathogenic and non-pathogenic gram-negative bacteria can produce extracellular vesicles.

[00:51:48]Figure 4.2 and OIMVs are formed. OIMVs are formed from the outer membrane and the cell surface membrane. So, my bus this is basically the cell surface membrane.

[00:52:01]This is basically the outer membrane.

[00:52:03]How about OIMV mega get them? We can see outer membrane be present here or cell membrane be present there.

[00:52:11]OIMVs can contain ATP and DNA.

[00:52:15]I got a OIMV to compare getting OMVs.

[00:52:17]So, OMV is only made up of the outer membrane. It is only made up of the outer membrane.

[00:52:25]Whereas the OIMV is made up of the outer membrane as well as the cell membrane.

[00:52:32]How about getting here? Plasmids which are small circular DNA are found in the OIMV. But, they are not found in the OMVs.

[00:52:45]With reference to figure 4.2, suggest why fewer OIMVs are formed than OMVs.

[00:52:54]It is because we can see how many bars OIMV formed getting here.

[00:53:00]Save for my outer membrane.

[00:53:02]Can get them here.

[00:53:04]Fold earlier or outer membrane eventually pinch off getting OIMV banana.

[00:53:10]On the other hand, OIMV banana getting here how many bars cellular content he chaiye how many bars cell membrane be bulge getting here how many bars getting the peptidoglycan cell wall here this is the peptidoglycan cell wall.

[00:53:23]How many bars is point per break getting here and eventually is about OIMV banana. So, forming an OIMV is a comparatively more complex process.

[00:53:33]Because the cell membrane as well as the outer membrane has to bulge and cell components also have to be a part of the OIMV.

[00:53:45]More complex process to form an OIMV since the folding of both cell membrane and the outer membrane has to occur.

[00:54:22]Suggest why ATP is found within OIMVs but not in OMVs. I might have ATP to hold the ATP.

[00:54:29]A bacterial cytoplasm is present over I might have to get the inside of the plasma in ATP present over. The cytoplasm ATP would be transferred into the OIMV because I might have to get the inside of the OIMV in cellular content be present over. Cytoplasm be present over. On the other hand, OMVs may cytoplasm present over. Cytoplasm may be present over. So, I might have to get the inside of the ATP present over.

[00:54:54]OIMVs consist of bacterial cytoplasm in which ATP is found.

[00:55:14]Suggest and explain why the discovery that OIMVs contain DNA. Guess in the past DNA because they have plasmids.

[00:55:21]Plasmids are basically cytoplasmic DNA, that circular cytoplasmic DNAs.

[00:55:26]Why the discovery that OIMVs contain DNA has implications for antibiotic resistance. I might have antibiotic resistance to with the I might have antibiotic resistance to with the I might have to get the bacteria may a mutated antibiotic resistance gene or a plasmid cytoplasmic circular DNA if that develops an antibiotic resistant allele it can transfer that allele to other bacteria and thus it can be a reason of antibiotic resistance to spread.

[00:56:04]The plasmid within OIMVs can mutate to form a resistant allele which can then be passed to other bacteria by vertical transmission such as transformation.

[00:56:58]Clear? Any questions?

[00:57:07]Okay.

[00:57:08]Let's move to question number six and then wrap up this paper.

[00:57:14]Okay. So question number 16 in the pulmonary circulation of a mammal deoxygenated blood becomes oxygenated when red blood cells pass through alveolar capillaries and hemoglobin within the cells combines with oxygen.

[00:57:30]The blood returns to the heart to be pumped around the systemic circulation.

[00:57:34]Describe the sequence of events occurring in the heart that allows blood returning in the pulmonary circulation to then enter the systemic circulation.

[00:57:44]You should include in your description the names of the relevant blood vessels of the pulmonary circulation and systemic circulation that are connected to the heart, reference to blood pressure changes that cause the opening and closing of valves. You do not need to include the details of the control of cardiac cycle.

[00:58:02]Okay.

[00:58:03]So, basically one second, my tablet got disconnected.

[00:58:12]So, when they're saying you do not need to include the details of control of the cardiac cycle, we basically don't have to talk about the sinoatrial node and everything.

[00:58:19]What we have to talk about over here is how the blood which is entering the heart is entering into the system.

[00:58:32]The sequence of events occurring in the heart that allows blood returning in the pulmonary circulation to then enter the systemic circulation.

[00:58:48]It comes where the pulmonary vein. And when it once it enters into the pulmonary vein, it then enters into the left atrium.

[00:58:58]When it enters into the left atrium, it then moves to towards the left ventricle where the AV valve.

[00:59:13]Bicuspid valve over there. Now, valve get through atria atrium the blood ventricle may I got that here. Then the ventricles pressure starts to increase.

[00:59:25]When the ventricles pressure starts to increase, the first thing which happens is that the AV valves closes to prevent the backflow of blood to the atrium.

[00:59:34]The ventricles pressure increases. When it increases above the aortic pressure, the aortic valve or the semilunar valve in the aorta, that opens. And once it opens, the blood from the left ventricle enters into the aorta, and then through the aorta, it is supplied to the rest of the body.

[00:59:56]Clear? Any questions?

[01:00:41]Figure 6.1 is a drawing of a hemoglobin molecule to show its globular structure.

[01:00:45]Describe the quaternary structure of a hemoglobin molecule. So, my best quaternary structure may two or more than two polypeptide chains associate via hydrogen bonding, hydrophobic interactions, ionic bonding, or disulfide bonds, so my best quaternary structure form with that.

[01:01:04]My best hemoglobin key quaternary structure may we have four polypeptide chains, two alpha chains and two beta chains, which associate via these four bonds to form the quaternary structure.

[01:01:20]The hemoglobin molecule consists of two alpha globin chains and two beta globins which associate via hydrogen bonds formed between the R groups of the four chains.

[01:02:05]Explain how a hemoglobin molecule can become fully saturated with oxygen to form oxyhemoglobin.

[01:02:11]So, basically a hemoglobin molecule has a four heme groups.

[01:02:16]Um Each heme group basically has an iron ion in the center. One oxygen molecule can bind to one iron ion. So, a total of four oxygen molecules binding to the iron ion forms the oxyhemoglobin.

[01:02:39]Iron ion is present in each heme group of the four chains.

[01:03:00]One oxygen molecule can bind to one iron ion.

[01:03:12]A hemoglobin molecule >> can become fully saturated when all four iron ions are bound to four oxygen molecules.

[01:03:45]Okay.

[01:03:47]So, that's it for this paper. We shall start with a new paper due tomorrow.

[01:03:52]Till then, take care. Allah Hafiz.