Natural Exam Essay Minimum 2500 Words

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Science

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Notes: Although there is a minimum word count of 2500 words for the entire exam (about 625 words or more per question), you will find that it is likely going to require more than the minimum to fully answer the questions. You may not copy or quote from any source. All information must be re-written in your own words.

Question 1: Membranes

Membranes are the primary structural elements of cells and, more than any other structure, provide the integrity of what makes a cell a cell. Discuss the structure of membranes, their role in compartmentalization, and the mechanisms by which some molecules are excluded and others are allowed to enter the cell. Include in your answer:

a. the reasons that molecules would be excluded from passage across a membrane and how membranes are used to compartmentalize the cell

b. the mechanisms by which some molecules are allowed passage across the membrane

c. how molecules are transported into a cell against their concentration gradients

Question 2: Enzymes, Metabolic Pathways and Bioenergetics

Describe the production of pyruvate from glucose and the net increase of ATP during glycolysis. Include in your answer:

a. the structure of proteins and the particular nature of proteins important to enzyme action and the roles of coenzymes, cofactors and allosteric regulators

b. a description of coupled reactions that drive metabolic pathways and the general reasons why some molecules are unstable while others are stable

c. a description of the structure of ATP, the reasons for which it is unstable, and the role(s) of the phosphate group once transferred to another molecule

Question 3: Electron Transport Chains

Electron transport chains found in chloroplasts and mitochondria are central to photosynthesis and respiration for powering most life. Describe the electron transport chains of photosynthesis and respiration and their functions in using light to transform stable molecules into unstable molecules (photosynthesis) and using these unstable molecules to fuel cells (respiration). Include in your answer:

a. the special properties of chlorophyll and ATP synthase

b. the sequences of events in both photosynthetic and respiratory electron transport chains from the sources to the sinks

c. the overall function of each electron transport chain that drives the chemical pathways each serves

Question 4: Photosynthesis

Describe the structure of the chloroplast and the mechanisms of photosynthesis. Include in your answer:

a. the structure and function of the different compartments and membranes of the chloroplast

b. the role of light in the photosynthetic process (photolysis and photophosphorylation)

c. the synthesis of sugars from carbon dioxide and the products of photophosphorylation (photosynthetic carbon reduction cycle)

d. a comparison of C-3 and C-4 plants and adaptations of C-4 plants for tropical and desert habitats

References Immediately following the essay, two lines below the last line of your last answer (do not skip to a following page), list all sources used in writing your essay to answer the question. Do not use in-text citations and do not use footnotes. Simply list your sources in this “References” section. You must have a References section with at least five references which you have used in preparing your answers

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Explanation & Answer

Attached.

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Biology Discussion Questions
Question 1: Membranes
It is true that membranes are actually the primary structural elements to the cells. As
some research says, it is a selective barrier that permits many things to pass through but also
stops others. Some of those things are the molecules as well as ions or even some other small
particles.

However there are some reasons as to why molecules would not be included from

the passage across the membrane and one of them being that, the effective function of a cell
requires control of substances that can enter or exit a membrane. The primary trait of a cell is the
selective permeability which allows molecules to cross quickly, while others are restricted.
Small molecules that are nonpolar can cross a membrane through diffusion, but ions and large
molecules may not. The reason why ions are excluded from through membrane is that it is
repelled by charged molecules. Besides, even a small hydrogen ion cannot permeate the cell
membrane through the fatty acid. Therefore, an ion that needs to enter a cell due to a high
concentration on one side can only do the same using protein channels embedded between lipids.
Moreover, molecules such as glucose cannot easily permeate the cell membrane because it is
large. That makes their process of slipping across the membrane through diffusion slow. They
must resort to channels of ion and precise transporters that actually require energy output to
move at a normal speed.

Surname 2

On the other hand, membranes are used in compartmentalizing the cell because
intracellular membranes develop enclosed compartments which are separate from the cytosol,
therefore, offering the cell with the functionally specific aqueous space. The key intracellular
compartments necessary to eukaryotic cells are as follows. The nucleus has the major genome,
and it is the principal site of DNA and RNA synthesis. The surrounding cytoplasm entails
cytosol and the cytoplasmic organelles that are suspended in it. Moreover, cytosol constitutes
more than half of the total cell volume. It also undertakes cell intermediary metabolism where
many reactions of small molecules get degraded while others get synthesized to provide a
building block associated with macromolecules.
Question 1 b. The mechanisms
There are many ways that the molecules can use to pass across a membrane, for example,
passive mechanisms such as diffusion and active process that calls for energy. Diffusion is
actually the movement of the particles to offset the imbalance in concentration. Molecules that
mostly involve in diffusion include water because they easily penetrate the membrane of a cell.
The second one is active transport where a molecule moves against the gradient. That calls for
energy, and a good example is sodium pump (Na+/K+ ATPase), which preserves the resting
position of a cell. The protein also uses the energy gotten from ATP hydrolysis to just pump the
three sodium ions and also two potassium ions in the cell. Another location for ATP pump is
proton/potassium exchanger that creates the acidic atmosphere of the known stomach, therefore,
causing acidic reflux. Besides, proton pump inhibitor such as omeprazole is prescribed to the
patients with the ulcers or even acid reflux so as to help in the decrease of acidity in a gut.
Question 1 c. The molecules transportation

Surname 3

The first aspect is secondary active transport where multiple molecules move uphill or
against the gradient. For instance, SGLT2 is a transporter of glucose that allows molecules into
cells by bringing sodium molecules as well. When sodium enters a cell, the energy produced by
it while traveling down a gradient is enough for the powering of glucose into cells. The
molecules move in the same direction; therefore, they are known as symporter. Some protein
helps molecules to move in different directions, and that is called antiporters mechanism. That
concept is known as sodium/calcium exchanger mechanism utilized in the...


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