A) crabby the crab lives in the ocean just off the east coast of the united stat
ID: 209158 • Letter: A
Question
A) crabby the crab lives in the ocean just off the east coast of the united states. one day, a young child catches Crabby and wants to take him home as pet. The child's family had a freshwater pound in their backyard, and the child plans to allow crabby to live in the pond. Using your knowledge of diffusion, osmosis, and tonicity, explain why the move to the freshwater pond will be deadly of crabby
B) Concisely describe the fluid mosaic model of the plasma membrane. Do not draw a picture.
C) Consider the insulin-producing cells in the pancreas and innate immune cells such as macrophages. Why are endocytosis and exocytosis important in these cells? which process is more important for each cell type?
D) Why is a active transport necessary in living organisms? what kinds of disorders could result from problems with active transport?
E) Explain 3 of the 6 major functions of membrane proteins.
5.
A) A certain poison acts by binding to the enzyme ATP synthase, which catalyzed the formation of ATP. Binding of this poison causes the enzyme to become inactive. If excess ADP is added in the presence of this poison, the poison is no longer effective.
What purpose does ADP serve in the example?
What type of inhibitor is the poison? what evidence led you to this conclusion?
What is the difference between an exergonic and endergonic reaction? what is the effect on free energy change and entropy of the system of each of these types of reactions?
6. Propose 3 ways that this pathway could be disrupted in patients with type 2 diabetes and suggest a way that one of these problems could be treated medically.
Question 4, Membranes and Cellular Transport (15 points total) A) (3 points) Crabby the crab lives in the ocean just off the east coast of the United States. One day, a young child catches Crabby and wants to take him home as a pet. The child's family had a freshwater pond in their backyard, and the child plans to allow Crabby to live in the pond. Using your knowledge of diffusion, osmosis, and tonicity, explain why the move to the freshwater pond will be deadly for crabby. 3 B) (3 points) Concisely describe the fluid mosaic model of plasma membrane. Do not draw a picture. Do not use more than 3 statements. c) (3 points) Consider the insulin producing cells in the pancreas and innate immune cells such as macrophages. Why are endocytosis and exocytosis important in these cells? Which process is more important in each cell type? Explain your answer.Explanation / Answer
5.a] Osmosis is the movement of water molecules from a higher concentration [ dilute solution] to a lower concentration[ concentrated solution] through a semi permeable membrane [it is a term used only for movement of water molecules] .
Diffusion is the movement of fluid molecules from a higher to a kower concentration till they are evenly dispersed.
Tonicity is the relative concentration of solutes dissolved in a solution which determines the direction and extent of diffusion. In short, all three are related and determine the movement of molecules along the concentration.
Ocean water is highly saline [ salty] with a high concentration of various salts dissolved in it . Aquatic animals living in seas and oceans have adjusted to it and there is an equilibrium between their body fluid and the surrounding saline water. When the crab is moved to fresh water, the following changes will occur:
* The water from the pond will start moving inside the crab's body by osmosis, because the pond water is fresh water and has a much higher water concentration as compared to the crab's body fluids.
* The solute molecules will begin to diffuse out of the crab's body to be at equilibrium with the surrounding pond water.
The crab will die due to accumulation of excess water in its cells and a dilution of its body fluids.
b] The plasma membrane is trilaminar i.e. it is made up of three layers of biomolecules-- two layer of phospholipids and a layer of protein. However, these layers are not rigid but in a state of fluidity which is what makes the plasma membrane soft and flexible.
The phospholipid molecules have a hydrophilic[ water loving] head and a hydrophobic [ water fearing ] head. The layers are arranged in such a way that the hydrophilic heads point outwards and the hydrophilic tail forms the center of the bilayer.
Proteins and some cholesterol molecule lie embedded in the lipid bilayer, giving the membrane the look of a mosaic. These molecules can move or float in the lipid bilayer and for this reason this structure of plasma membrane is called the ' fluid mosaic model '. It is very important for the transport of various molecules accross the PM.
c] Endocytosis is a cellular process by which a cell engulfs a molecule or substance outside the cell and brings it into the cytoplasm. It is an important way of feeding for many unicellular organisms.
Exocytosis is the process by which cells release the substance synthesised by them. The vesicles containing the synthesised substance fuse with the plasma membrane and release their content to the outside of the cell.
Exocytosis is important for insulin producing pancreatis cells, because insulin has to be discharged into the blood stream for its function i.e to convert excess blood sugar into glycogen.
Endocytosis is important for macrophages because their fonction is to target and kill by engulfing the microbes which might have entered our body.
d] Active transport is that in which the movement of molecules is facilitated across a cell membrane , into a region of higher concentration with the help of enzymes. This process requires energy. It is absolutely essential for a cell to perform its normal functions. A very important active transport system is the sodium-potassium pump. This helps in the proper functioning of the nervous system by maintaining a difference in ion concentration between the outside and inside of the nerve cells. There are many more examples where the active transport is essential for the proper functioning of the body . Many types of complications will arise if the active transport system is disturbed.
e] ] Functions of membrane proteins -- They perform several functions essential for the survival of living organisms.
* Membrane receptor proteins relay signals through the PM between the cells external and internal environments.
These signals are important as they carry instructions to and from the cell. For example, the hormones reach the target cells or organs, then it is the receptor proteins which transport the signal to the inside of the cells for further action.
* Transport proteins move molecules and ions across the cell membrane. This is necessary for the synthesis or breakdown of important molecules. For example, glucose molecules are transported inside the cell for respiration and release of energy.
* Cell adhesion molecules allow cells to identify with other cells and interact . For example, cells involved in immune response of the body have antigen binding sites on their PM which helps them to recognise and bind to the antigens which have entered the body.
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