BIO152 Exam 4 UPDATED ACTUAL
Exam Questions and CORRECT Answers
Transpiration - CORRECT ANSWER - Transpiration is the loss of water from the plant
through evaporation at the leaf surface. It is the main driver of water movement in the xylem.
Lumen - CORRECT ANSWER - The sources mention the thylakoid lumen as the internal
space enclosed by the thylakoid membrane within a chloroplast. Hydrogen ions accumulate in
this space during the light-dependent reactions of photosynthesis. The term 'lumen' can also refer
to the internal cavity of tubular structures in other biological contexts, though the sources
primarily use it in the context of the thylakoid.
Cuticle - CORRECT ANSWER - The cuticle is a waxy covering on the outer surface of
aerial parts of land plants, such as leaves and stems. It is produced and secreted by epidermal
cells. Its function is to minimize water loss.
Stoma (stomata) - CORRECT ANSWER - A stoma (plural: stomata) is a pore that
penetrates the waxy cuticle on the surface of plant leaves. It allows for effective gas exchange
with the environment. In gymnosperms and angiosperms, each pore is flanked by two specialized
plant cells called guard cells. The entire structure, including the pore and guard cells, is referred
to as a stoma.
Anatomy of Photosynthetic Tissues - CORRECT ANSWER - Leaves are the main sites for
photosynthesis in most terrestrial environments. The outer surface layer is the epidermis, present
on both upper and lower sides. Epidermal cells are generally not photosynthetic but help balance
gas exchange and water loss. Below the epidermis is the mesophyll ('middle leaf'), which
contains the photosynthetic cells. The mesophyll typically has two layers: palisade parenchyma
(column-shaped, tightly packed cells, high chloroplast concentration) and spongy parenchyma
(loosely arranged, irregularly shaped cells). Both layers contain many chloroplasts. Stomata are
pores on the leaf surface, often more numerous on the underside. They are surrounded by guard
cells (the only epidermal cells with chloroplasts) that regulate their opening and closing. Leaves
contain vascular bundles composed of xylem (transports water and minerals to the leaves) and
phloem (transports photosynthetic products from the leaf).
,Cuticle and Stoma Pros and Cons - CORRECT ANSWER - Cuticle: Pro: Helps to
minimize water loss from the plant's aerial surfaces. Con: Creates a barrier that prevents effective
gas exchange. Stomata: Pro: Provide pores for effective gas exchange, allowing CO2 to enter for
photosynthesis and O2 to leave. Con: Are also the primary sites for water loss through
transpiration. Their opening and closing are regulated by guard cells to balance the need for gas
exchange against the need to conserve water.
Autotroph - CORRECT ANSWER - An autotroph is an organism that can produce its own
food. They synthesize carbohydrates from light and carbon dioxide through photosynthesis.
Examples include plants, certain bacteria, and algae.
Heterotroph - CORRECT ANSWER - A heterotroph is an organism that must rely on
other organisms for their organic compounds or food source. They obtain energy by consuming
other organisms. Examples include animals and some plants (like holo-parasitic plants lacking
chlorophyll).
Photosynthesis - CORRECT ANSWER - Photosynthesis is the process by which green
plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll
pigments, primarily converting carbon dioxide and water into glucose and oxygen.
Photosynthesis - CORRECT ANSWER - The process by which certain organisms convert
solar energy (sunlight) into chemical energy, used to build carbohydrate molecules from light,
carbon dioxide, and water, releasing oxygen into the atmosphere.
Pigment - CORRECT ANSWER - A molecule that absorbs light. In plants, pigment
molecules like chlorophyll absorb visible light for photosynthesis and act as biological 'sun
catchers'. Different pigments absorb different wavelengths of light and reflect others.
Wavelength - CORRECT ANSWER - A measure used to describe and measure the
manner in which solar energy (electromagnetic radiation) travels, with different wavelengths
corresponding to different colors of visible light, shorter wavelengths having higher energy and
longer wavelengths having lower energy.
, Carboxylation - CORRECT ANSWER - The first step of the Calvin cycle, also referred to
as carbon fixation, where carbon dioxide (CO2) is added to ribulose bisphosphate (RuBP),
catalyzed by the enzyme RuBisCO, forming a six-carbon compound that breaks down into two
three-carbon intermediates (3-PGA).
Intermediate - CORRECT ANSWER - A temporary molecule produced step-by-step as a
substrate is modified in a metabolic pathway, eventually yielding a final product. For example,
glucose-6-phosphate is an intermediate between glucose and pyruvate, and in the Calvin cycle,
3-PGA is an intermediate formed after carbon fixation.
Reduction - CORRECT ANSWER - The second step of the Calvin cycle, where
intermediate molecules (specifically 3-PGA) are energized by ATP and reduced by NADPH,
converting the 3-PGA molecules into glyceraldehyde 3-phosphate (G3P).
Autotrophs - CORRECT ANSWER - Organisms, like plants, that make their own food by
converting solar energy and carbon dioxide into chemical energy in the form of carbohydrates
through photosynthesis.
Heterotrophs - CORRECT ANSWER - Organisms, like animals, that obtain energy by
consuming other organisms for their organic compounds or food source.
Light-dependent reactions - CORRECT ANSWER - The part of photosynthesis that occurs
at the thylakoid membrane, converting light energy into chemical energy using water and
releasing oxygen as a byproduct.
Calvin cycle - CORRECT ANSWER - The part of photosynthesis that takes place in the
stroma, using the chemical energy (ATP and NADPH) from the light reactions to capture carbon
from CO2 and assemble sugar molecules (carbohydrates).
ATP - CORRECT ANSWER - An energy carrier molecule produced during the light-
dependent reactions that transports chemical energy to the Calvin cycle, providing energy for the
process.
Exam Questions and CORRECT Answers
Transpiration - CORRECT ANSWER - Transpiration is the loss of water from the plant
through evaporation at the leaf surface. It is the main driver of water movement in the xylem.
Lumen - CORRECT ANSWER - The sources mention the thylakoid lumen as the internal
space enclosed by the thylakoid membrane within a chloroplast. Hydrogen ions accumulate in
this space during the light-dependent reactions of photosynthesis. The term 'lumen' can also refer
to the internal cavity of tubular structures in other biological contexts, though the sources
primarily use it in the context of the thylakoid.
Cuticle - CORRECT ANSWER - The cuticle is a waxy covering on the outer surface of
aerial parts of land plants, such as leaves and stems. It is produced and secreted by epidermal
cells. Its function is to minimize water loss.
Stoma (stomata) - CORRECT ANSWER - A stoma (plural: stomata) is a pore that
penetrates the waxy cuticle on the surface of plant leaves. It allows for effective gas exchange
with the environment. In gymnosperms and angiosperms, each pore is flanked by two specialized
plant cells called guard cells. The entire structure, including the pore and guard cells, is referred
to as a stoma.
Anatomy of Photosynthetic Tissues - CORRECT ANSWER - Leaves are the main sites for
photosynthesis in most terrestrial environments. The outer surface layer is the epidermis, present
on both upper and lower sides. Epidermal cells are generally not photosynthetic but help balance
gas exchange and water loss. Below the epidermis is the mesophyll ('middle leaf'), which
contains the photosynthetic cells. The mesophyll typically has two layers: palisade parenchyma
(column-shaped, tightly packed cells, high chloroplast concentration) and spongy parenchyma
(loosely arranged, irregularly shaped cells). Both layers contain many chloroplasts. Stomata are
pores on the leaf surface, often more numerous on the underside. They are surrounded by guard
cells (the only epidermal cells with chloroplasts) that regulate their opening and closing. Leaves
contain vascular bundles composed of xylem (transports water and minerals to the leaves) and
phloem (transports photosynthetic products from the leaf).
,Cuticle and Stoma Pros and Cons - CORRECT ANSWER - Cuticle: Pro: Helps to
minimize water loss from the plant's aerial surfaces. Con: Creates a barrier that prevents effective
gas exchange. Stomata: Pro: Provide pores for effective gas exchange, allowing CO2 to enter for
photosynthesis and O2 to leave. Con: Are also the primary sites for water loss through
transpiration. Their opening and closing are regulated by guard cells to balance the need for gas
exchange against the need to conserve water.
Autotroph - CORRECT ANSWER - An autotroph is an organism that can produce its own
food. They synthesize carbohydrates from light and carbon dioxide through photosynthesis.
Examples include plants, certain bacteria, and algae.
Heterotroph - CORRECT ANSWER - A heterotroph is an organism that must rely on
other organisms for their organic compounds or food source. They obtain energy by consuming
other organisms. Examples include animals and some plants (like holo-parasitic plants lacking
chlorophyll).
Photosynthesis - CORRECT ANSWER - Photosynthesis is the process by which green
plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll
pigments, primarily converting carbon dioxide and water into glucose and oxygen.
Photosynthesis - CORRECT ANSWER - The process by which certain organisms convert
solar energy (sunlight) into chemical energy, used to build carbohydrate molecules from light,
carbon dioxide, and water, releasing oxygen into the atmosphere.
Pigment - CORRECT ANSWER - A molecule that absorbs light. In plants, pigment
molecules like chlorophyll absorb visible light for photosynthesis and act as biological 'sun
catchers'. Different pigments absorb different wavelengths of light and reflect others.
Wavelength - CORRECT ANSWER - A measure used to describe and measure the
manner in which solar energy (electromagnetic radiation) travels, with different wavelengths
corresponding to different colors of visible light, shorter wavelengths having higher energy and
longer wavelengths having lower energy.
, Carboxylation - CORRECT ANSWER - The first step of the Calvin cycle, also referred to
as carbon fixation, where carbon dioxide (CO2) is added to ribulose bisphosphate (RuBP),
catalyzed by the enzyme RuBisCO, forming a six-carbon compound that breaks down into two
three-carbon intermediates (3-PGA).
Intermediate - CORRECT ANSWER - A temporary molecule produced step-by-step as a
substrate is modified in a metabolic pathway, eventually yielding a final product. For example,
glucose-6-phosphate is an intermediate between glucose and pyruvate, and in the Calvin cycle,
3-PGA is an intermediate formed after carbon fixation.
Reduction - CORRECT ANSWER - The second step of the Calvin cycle, where
intermediate molecules (specifically 3-PGA) are energized by ATP and reduced by NADPH,
converting the 3-PGA molecules into glyceraldehyde 3-phosphate (G3P).
Autotrophs - CORRECT ANSWER - Organisms, like plants, that make their own food by
converting solar energy and carbon dioxide into chemical energy in the form of carbohydrates
through photosynthesis.
Heterotrophs - CORRECT ANSWER - Organisms, like animals, that obtain energy by
consuming other organisms for their organic compounds or food source.
Light-dependent reactions - CORRECT ANSWER - The part of photosynthesis that occurs
at the thylakoid membrane, converting light energy into chemical energy using water and
releasing oxygen as a byproduct.
Calvin cycle - CORRECT ANSWER - The part of photosynthesis that takes place in the
stroma, using the chemical energy (ATP and NADPH) from the light reactions to capture carbon
from CO2 and assemble sugar molecules (carbohydrates).
ATP - CORRECT ANSWER - An energy carrier molecule produced during the light-
dependent reactions that transports chemical energy to the Calvin cycle, providing energy for the
process.
