Mod 2

Question 1

Two molecules of glucose are joined together by a _____________ bond, this reaction ______________ a molecule of water and is a(n) ________________ reaction.

Answer 1

glycosidic / forms and releases / anabolic

Question 2

An animal will find it difficult to ___________ produce ______________ without ___________ in its diet.

Answer 2

anabolically / new protein / essential amino acids

Question 3

A case was reported in the Annals of Internal Medicine, of a 17 years old male who progressively lost most of his vision starting at age 15 and was legally blind by 17. Otherwise, he appeared normal, with average height and weight. After questioning by medical professionals, the boy revealed that every day he ate, a portion of hot potatoe fries, and would snack on Pringles, white bread, and slices of processed ham or sausage. He ate no other foods apart from these, ever. What might have caused his blindness? What could the boy do to achieve a healthier diet? What help could he be given? How could this situation have been prevented?

Answer 3

• The lack of vitamins and minerals (e.g. Vitamins B) in his diet may cause his blindness. Vitamins usually act as a coenzyme, while the metabolism reactions need enzymes, and the vitamins will lock on them and help them finish the “work”. So, vitamins and minerals play an important role in building up tissues. Optic nerve is one of the tissues that need to “repair” (old cells dead, new cells need to form) all the time, with the insufficient vitamins and minerals in his body, his optic nerve may have not been able to “repair” which lead to blindness. His daily diet is mainly carbohydrates and high in sodium, etc. He needs to increase the intakes of other macronutrients and micronutrients (more F&V…)

Question 4

The enzyme that converts pyruvate to Acetyla-CoA and carbon dioxide is called pyruvate dehydrogenase and it is located in the mitochondria. If a dog had a mitochondrial deficiency and had an abnormally low amounts of mitochondria, how might this affect the dog’s metabolism?

Answer 4

• (some functions of mitochondria) 1. ATP production
  2. calcium homeostasis
  3. regulation of innate immunity
  4. programmed cell death 5. stem cell regulation
  With the abnormally of low amounts of mitochondria, the dog may not normally achieve those functions (e.g. cannot produce enough energy for the normal functioning). The aerobic pathway will not happen in this dog.

Question 5

In a(n) _______________ cell, the ______________ is/are _____________ .

Answer 5

animal / nucleus / connected to the endoplasmic reticulum

Question 6

_____________ occurs in the _______________

Answer 6

Catabolism of fatty acids / peroxisome

Question 7

What might happen if a fish had a mutation that caused an amino group to be substituted for the OH group on the first ring of cholesterol?

Answer 7

• The fish will have a bad connective cell, so it may be difficult to get pass the embryo state.

Question 8

___________________ is _______________ the ______________ in _______________ .

Answer 8

The mitochondrion / wrapped around / the microtubules / sperm

Question 9

A ____________ caused a(n) ______________ in _______________ .

Answer 9

rise in CRH release / increase of exocytosis / a pituitary cell

Question 10

Describe what would happen from a physiological and cellular perspective if a salt-water fish was placed into fresh water

Answer 10

When the environment surround by the fish that has a lower concentration then before (fresh water), the water will transport from the outside into the fish. However, the urine system of the fish is not ready to “pump” the salts out, so the water will just stay in the fish. As a result, the cells of the fish get stress from the water that coming into the cell which will cause cell lysis.

Question 11

________________ confer(s) a(n) _______________ to _______________

Answer 11

Tight junctions / waterproofing quality / epithelial cells

Question 12

______________ muscle has _______________ but no ________________

Answer 12

Smooth / spindle shaped cells / branched fibres

Skeletal / striations / spindle shaped cells

Question 13

What would happen if cortisol exerted a negative feedback on the hypothalamus?

Answer 13

The hypothalamus is a part of the brain that plays a central role in regulating the body’s stress response through the hypothalamic-pituitary-adrenal (HPA) axis.

If cortisol were to exert a negative feedback on the hypothalamus, this would create a self-regulating mechanism to control the stress response.

Question 14

Throughout pregnancy the concentration of CRH in the blood progressively rises to reach 1,000 times
that of non-pregnant levels. What effects would you expect that might have on the physiology of the
pregnant woman.

Answer 14

Effects include regulating cortisol production, aiding in the maturation of fetal organs, influencing uterine contractions, modulating the immune system, preparing the body for stress and childbirth, and potentially affecting mood. CRH is important for supporting the growing fetus and adapting the mother’s body for pregnancy and childbirth, but its excessive or abnormal increase may lead to complications, highlighting the need for appropriate medical care during pregnancy.

Question 15

to measure photosynthesis a student places a (living) plant leaf inside a gas exchange system (like we used in the
lab classes). The leaf is illuminated with a satura�ng light intensity, but at different CO2 concentra�ons. When the
CO2 concentra�on is around 50 μmol mol-1 (versus ~ 400 μmol mol-1 for normal air), the student no�ces that there
is no net exchange of CO2. What does this tell us

Answer 15

When a plant leaf is exposed to saturating light intensity and a relatively low CO2 concentration (around 50 μmol mol-1), and there is no net exchange of CO2, it indicates that the plant has reached its CO2 saturation point for photosynthesis. At this point, increasing the CO2 concentration further does not significantly enhance photosynthesis because other factors, such as light intensity or nutrient availability, may become limiting.

Question 16

Explain how CAM photosynthesis leads to greater water-use efficiency than C3 or C4 photosynthesis. In your
answer describe which “feature” of CAM has the largest effect on water-use efficiency

Answer 16

the primary feature of CAM photosynthesis that leads to greater water-use efficiency is the temporal separation of CO2 uptake and carbon fixation. By taking in CO2 at night and storing it as malic acid, CAM plants can continue photosynthesis during the day with closed stomata, reducing water loss. This adaptation makes CAM plants well-suited to water-scarce environments and explains their higher water-use efficiency compared to C3 and C4 plants.

Question 17

What are similari�es and differences between autotrophic and heterotrophic modes of “nutri�on

Answer 17

Autotrophs can synthesize organic compounds from inorganic sources like carbon dioxide, using light energy or inorganic chemical reactions. Heterotrophs, in contrast, cannot produce organic molecules from inorganic sources and acquire them by consuming other organisms or organic matter. Autotrophs capture energy from the environment, while heterotrophs rely on consuming pre-formed organic compounds. Autotrophs often serve as primary producers, forming the basis of food chains, while heterotrophs include consumers, decomposers, and predators in ecosystems.

Question 18

What are the main products of the light reac�ons (non-cyclic photophosphoryla�on)?

Answer 18

ATP and NADPH, are the primary energy-rich compounds generated in the light reactions of photosynthesis. They provide the energy and reducing power necessary for the synthesis of organic molecules, including sugars, in the subsequent dark reactions (Calvin cycle) of photosynthesis.

Question 19

What is the main reason plants transpire (evaporate) large amounts of water from their leaves?

Answer 19

ChatGPT
Plants transpire (evaporate) water from their leaves primarily for essential physiological functions. This process facilitates the uptake of water and nutrients from the roots, supports photosynthesis by providing water for the reaction, helps cool the plant, regulates turgor pressure, and aids in the transport of nutrients. While transpiration is crucial, plants have mechanisms to control it to prevent excessive water loss when necessary.

Question 20

C3 photosynthesis has one major drawback. What is that drawback and how is it solved by C4 photosynthesis

Answer 20

C4 photosynthesis solves the major drawback of photorespiration in C3 plants by spatially separating the initial carbon fixation and the subsequent concentration of carbon dioxide around RuBisCO. This separation minimizes oxygen exposure to RuBisCO and allows C4 plants to use carbon dioxide more efficiently, even in conditions where photorespiration is more likely to occur. As a result, C4 plants are better adapted to environments with high temperatures and limited water availability.

Question 21

Photosynthesis involves reduc�on/oxida�on of CO2? Bonus Ques�on: what does this mean in terms of
electrons

Answer 21

Photosynthesis involves the reduction of carbon dioxide (CO2) to form glucose and other organic molecules. Reduction is the gain of electrons, and in photosynthesis, CO2 gains electrons. This process relies on the oxidation of water molecules (H2O), which lose electrons and produce oxygen (O2) as a byproduct. These redox reactions in photosynthesis convert light energy into chemical energy stored in glucose.

Question 22

Why is rubisco’s oxygenase ac�vity problema�c?

Answer 22

Rubisco’s oxygenase activity is problematic because it can lead to photorespiration, a wasteful process in which Rubisco binds with oxygen instead of carbon dioxide. Photorespiration is energy-intensive, reduces growth, and increases water loss in plants. To mitigate this problem, some plants have evolved adaptations like C4 or CAM photosynthesis, which minimize the impact of Rubisco’s oxygenase activity and improve carbon fixation efficiency.

Question 23

Photosynthesis is respira�on in reverse. Discuss.

Answer 23

Photosynthesis and respiration are interconnected processes that can be seen as reversals of each other in terms of inputs and outputs. Photosynthesis captures energy (light) and carbon dioxide to produce glucose, storing energy. Respiration releases energy by breaking down glucose, producing carbon dioxide and water. While distinct, these processes are vital for energy flow and carbon cycling in ecosystems and life on Earth.

Question 24

What are the roles of oxygen in photosynthesis?

Answer 24

Oxygen plays several important roles in photosynthesis:

Oxygen is produced as a byproduct during the light-dependent reactions of photosynthesis when water molecules are split in photolysis.
Oxygen participates in the electron transport chain and redox reactions, facilitating electron flow and contributing to the generation of ATP during photosynthesis.
Oxygen helps maintain the proton gradient across the thylakoid membrane, which is essential for ATP synthesis during chemiosmotic coupling.
While oxygen is primarily associated with respiration, it indirectly supports energy production in photosynthesis by participating in these vital processes.

Question 25

Which photosynthe�c pathway (C3, C4, CAM) has the lowest “water cost” of photosynthesis? Why

Answer 25

Among the three photosynthetic pathways (C3, C4, and CAM), the C4 pathway is generally considered to have the lowest “water cost” of photosynthesis. This is because C4 plants have evolved several structural and biochemical adaptations that minimize water loss through transpiration while maximizing carbon fixation. Here’s why C4 photosynthesis is more water-efficient:

Question 26

The main purpose of Kreb’s cycle is to generate ATP. Discus

Answer 26

the primary purpose of the Krebs Cycle is to generate high-energy electron carriers (NADH and FADH2) and to further oxidize acetyl-CoA, not to produce ATP directly. The real production of ATP occurs later in the electron transport chain, where these high-energy electrons are used to create a proton gradient that drives ATP synthesis.

Question 27

Explain how glycolysis, Kreb’s cycle and the (mitochondrial) electron transport chain work together to support
the produc�on of ATP

Answer 27

Glycolysis initiates the breakdown of glucose, producing a small amount of ATP and NADH. The Krebs Cycle further oxidizes pyruvate from glycolysis and generates additional NADH and FADH2. These high-energy electron carriers feed into the mitochondrial electron transport chain, creating a proton gradient. The flow of protons back across the inner mitochondrial membrane through ATP synthase drives the production of ATP. These interconnected processes efficiently extract energy from glucose and convert it into ATP, the cell’s primary energy source.

Question 28

Why (or why not) might a plant be able to swap between C3 and C4 photosynthesis, or vice versa

Answer 28

the differences in leaf anatomy, enzyme specificity, genetic regulation, and evolutionary adaptations make it extremely challenging for a plant to switch between C3 and C4 photosynthesis or vice versa. These pathways are specialized for specific environmental conditions, and their adaptations are not easily reversible within a single plant’s lifetime.

Question 29

Explain how compartmenta�on is important for func�on of chloroplasts and mitochondria

Answer 29

In chloroplasts, it separates the light-dependent reactions in thylakoid membranes from the light-independent reactions in the stroma, preventing interference and enabling efficient photosynthesis.

In mitochondria, compartmentalization divides the electron transport chain and ATP synthesis in the inner mitochondrial membrane and the Krebs Cycle in the mitochondrial matrix. This separation ensures efficient ATP production, minimizes the formation of reactive oxygen species (ROS), and supports cellular respiration.

Overall, compartmentalization enhances the efficiency and coordination of energy metabolism in these organelles, allowing for specialized reactions to occur without interference and providing a controlled environment for various metabolic pathway

Question 30

A scien�st conducts an experiment where they carefully inject lots of H+ ions into just the matrix of a
mitochondrion. What effect would we expect for this to have on respira�on and wh

Answer 30

injecting excess H+ ions into the mitochondrial matrix would disrupt the normal proton gradient and impair ATP synthesis through oxidative phosphorylation. Cellular respiration would be less efficient, and the energy expended for pumping protons across the inner mitochondrial membrane would be wasted. This disruption could lead to a decrease in ATP production and may have detrimental effects on cellular energy balance and metabolic processes.

Question 31

A scien�st is conduc�ng an experiment on Amoeba, a single-celled eukaryote that has mitochondria. The
scien�st injects NADH and FADH2 into the cell. Which of the following would be most likely to occur

Answer 31

Injecting NADH and FADH2 into an Amoeba cell would likely stimulate cellular respiration, increasing the flow of electrons through the mitochondrial electron transport chain. This would lead to an increase in ATP production, providing the cell with more energy for its various functions. However, the introduction of these molecules should be done with caution, as it can disrupt normal redox balance and regulatory mechanisms if not properly managed.