BIO 251 Exam
(2026-2027 Edition)
Final Exam Questions with 100%
Correct Answers and Rationales |
Latest Update | Grade A+
,Name five fundamental characteristics shared by all 1. Cells
living organism. 2. Energy consumption
3. Information
4. Replication
5. Evolutionary adaptation
Describe the two components of cell theory. 1. All living things are made up of cell or cells.
2. Cells come from other cells.
Define energy, and describe the major forms it can take. Energy is the capacity to do work or to supply heat. Potential energy- may be
Understand in what way chemical bonds can be stored. Kinetic energy- may be available in the form of motion. When chemical
considered a form of energy. bonds are formed, energy is released. The internal energy of the system goes
down
Explain, both in mathematical terms and in plain English, ΔG(ibbs free energy) = ΔH (enthalpy) - T ΔS (entropy)
how changes in entropy and potential energy determine
whether or not a reaction is spontaneous. Understand If ΔG is negative (big loss of potential energy, and/or big gain of disorder): the
under what conditions a nonspontaneous reaction can reaction is Exergonic (Exit of energy). SPONTANEOUS
occur.
If ΔG is positive (big gain of potential energy, and/or big loss of disorder): the
reaction is Endergonic (Input of energy). NOT SPONTANEOUS
Explain and give examples of why proteins are essential -Enzyme Catalysis (chemistry)
to cell function. -Cell receptors (signalling and immune response)
-Transport (food uptake, e.g.)
-Support (cell/organism structure)
-Motion (muscles, flagella)
-Regulation (gene expression)
Sketch the basic structure of an amino acid, and Structure: Central carbon atom bonded to an amino group (-NH2), a carboxyl
describe why and how the side chains affect the function group (-COOH), a hydrogen atom and in the 4th position, a side group (R-
and structure of each amino acid. Group). The side chain is the chemical identity to the amino acid and extends out
from the backbone, making it possible for them to interact with each other and
with water. (Visual representation: slide 4)
Sketch a nucleotide, label its three basic parts, and A nucleotide has a sugar or deoxyribose group, a phosphate that is attached on
identify the 2', 3', and 5' carbons. the 5' carbon and an organic nitrogenous base which is attached to the 3'
carbon. Ribose has an -OH on the 2' carbon, Deoxyribose has a H' on the 2'
carbon.
Describe the primary, secondary, tertiary, and quaternary RNA's primary structure consists of a sequence of nitrogen-containing bases that
structures of RNA, and explain in what ways RNA differs contain information in the form of a molecular code. Its secondary structure
from DNA. includes short double helixes and structures called hairpins that holds RNA
strands together. Its tertiary and quaternary structures that fold secondary
structures into complex shapes or hold different RNA strands together. RNA has
Uracil instead of Thymine, it is single stranded, its ribose has an extra -OH group,
and it acts as a transcript of DNA expression. Also, DNA does not have a tertiary
and quaternary structure.
Explain why and how the secondary structure of DNA Complementary base pairing allows each strand of a DNA molecule to be copied
allows organisms to store and copy information. exactly, producing two daughter molecules. DNA's primary structure serves as a
mold or template for the synthesis of a complementary strand and DNA contains
the information required for a copy of itself to be made
Explain why RNA, and not DNA, was probably the first To make a copy of itself, the first living organism had to provide a template that
self-replicating molecule, and describe at least one piece could be copied and catalyze polymerization reactions that would link monomers
of experimental evidence that supports this hypothesis. into a copy of that template. RNA is capable of both.
One experimental evidence is by Wendy Johnston and David Bartel. They found
that ribozymes isolated in each round are copied, the molecules that result are
not identical in terms of their primary sequence because mutations were
introduced during the copying step. By isolating the best enzyme and copying
them in the next round, they continually selected ribozymes that were more
efficient. This was to mimic the process of natural selection
List the features shared by all carbohydrates. A molecule made up of a bunch of carbon, hydrogen, and oxygen. These atoms
are arranged in a few specific ways: they have a carbon atom that's bonded to a
carbonyl group (>C=O), several hydroxyl functional groups (-OH), and many C-H
bonds.
,Sketch several representative monosaccharides, Monosaccharide have a carbonyl group at various locations , several hydroxyl
illustrating three ways in which monosaccharides can functional groups at various locations, and many carbon-hydrogen (C-H) bonds
differ from one another. (energy). Linear form, ring form, alpha vs beta form.
Give examples of the four major functions that Raw materials: Sugars frequently furnish the raw "carbon skeletons" that are
carbohydrates can perform in cells (raw materials, used as a building blocks in the synthesis of important molecules. Amino acids
structure, cell identity, and chemical energy storage). use sugars as a starting point.
Structure: Cellulose and chitin, along with modified polysaccharide
peptidoglycan, are key to structural compounds. They form fibers that give cells
and organisms strength and elasticity.
Cell identity: Enormous number of structurally distinct monosaccharides make it
possible for an enormous number of unique oligosaccharides to exist. As a
result, each cell type and each species can display a unique identity
Chemical energy storage: Kinetic energy in sunlight is converted to chemical
energy stored in bonds of carbohydrates by photosynthesis.
Sketch a phospholipid's molecular structure, and explain Phospholipids have polar ends and nonpolar tails. The hydrophobic tails on the
why phospholipids spontaneously form bilayers in water. phospholipid molecules react with one another, and are repelled by water. The
polar head groups on the phospholipids are hydrophilic and react with water. For
these reasons, the phospholipids organize themselves in such a way as to
maximize the hydrophobic and hydrophilic interactions. The form that
accomplishes this the best is a bilayer.
Predict which way a certain substance will diffuse, given If a solution is hypertonic (the solution surrounding the cell has higher
its concentration on either side of a selectively concentration of solutes) water will rush out of the cell, shrinking it. If a solution is
permeable membrane. hypotonic, (the solution surrounding the cell has less concentration of solutes)
water will rush into the cell, enlarging it. If a solution is isotonic, (the
concentration of solute is the same inside and outside the cell) the water stays as
is.
Describe at least three ways in which membrane 1. Carrier proteins are in the phospholipid bilayer (the membrane) and they
proteins can help substances cross a cell membrane. transport large molecules: glucose and amino acids via the proteins by changing
the shape of them to make them more easy to transport.
2. Channel proteins: Used for ions (as the membrane is polar and so cannot
transport charged particles), and they can be gated and so selected about what
they allow through the protein.
3. Active Transport: Using ATP (energy) to move from a low to a high
concentration of solutes (with other diffusion it is from high to low diffusion) it
transports molecules using carrier proteins, the only difference is the direction
e.g. from a high or a low concentration.
4. Fluid mosaic model: Due to the phospholipids in the bilayer and the fluid like
consistancy of the membrane, small non polar (non charged particles/molecules)
can move through the membrane unaided.
Define the difference between passive transport and -Passive transport- movement is determined by concentration, movement from
active transport, and give examples of each. high to low. Doesn't require any energy. Oxygen and water and get into cells
easily (Diffusion of oxygen into an aerobically respiring cell).
-Active transport- Moving substances across a membrane against their
concentration gradients (high to low). Requires energy (ATP). Example: a cell
uses energy to pump out a substance already present in the extracellular fluid in
concentrations higher than inside the cell
Explain what molecular "zip codes" are and how they Molecular "zip codes" determines where a protein should be delivered. Inside
function. cells, materials are transported to their destinations with the help of molecular
"zip codes."
Describe the structural and functional importance of the This provides a structural framework within the cell, and plays a role in cell
cytoskeleton. division, movement, and transport.
Explain the dynamic nature of the cell. -Lots of chemical reactions occur each second
-Molecules constantly enter and exit across the plasma membrane
-Products move along protein fibers
The cytoskeleton continually grows and shrinks
, Understand the relationship between exergonic and ATP catalyzes endergonic reactions.
endergonic reactions and ATP. Example: ADP + Pi --> ATP
In exergonic reactions, ATP is released.
Example: ATP --> ADP + Pi
Describe the four components of cellular respiration. Part Glycolysis:
1. -starts by using ATP.
-Glucose is phosphorylated to form glucose-6-phosphate.
-An enzyme rearranges this to fructose-6-phosphate.
-A phosphate group is added, making fructose-1,6-biphosphate.
-2 ATP used before any ATP is produced
-NAD+ molecules are reduced
-2 ATP produced
-Final reaction in the sequence produces another 2 ATP
For each molecule of glucose processed, the net yield is 2 NADH, 2 ATP, 2
Pyruvate. Takes place in the cytosol.
Describe the four components of cellular respiration. Part Pyruvate Processing:
2. -Pyruvate reacts with a compound called coenzyme-A (CoA).
-CoA acts as a coenzyme by transferring an acetyl group to a substrate
-Pyruvate reacts with CoA to produce acetyl CoA
NADH produced. Takes place in the cytosol.
Describe the four components of cellular respiration. Part Krebs/Citric Acid Cycle:
3.
-Acetyl-CoA reacts with 4-carbon oxaloacetate to from 6-carbon citric acid
-Two of the 6-carbons of the citric acid leave as CO2
3 NADH, 1 FADH2, 1 ATP. Takes place in the mitochondrial matrix.
Describe the four components of cellular respiration. Part Electron Transport Chain:
4. -NADH and FADH2 is oxidized to NAD+ and FADH
-The electrons released by the NADH and the FADH2 is carried from one
complex to another by molecule ubiquinone and cytochrome c.
-Hydrogen that is also released by the oxidized NADH is pumped from the
matrix, through the complex, to the intermembrane
-Hydrogen protons runs the ATP synthase. The ATP synthase takes ADP and
one inorganic phosphate molecule (Pi). The ATP synthase puts the ADP and the
Pi together to make ATP.
-The electrons are moved from one complex to another, then they are added to 2
hydrogens and 1/2O2 to make H2O.
~29 ATP
Explain how cellular respiration and fermentation are Feedback inhibition. If ATP concentrations are high, the reaction rate is lowered.
regulated. ATP acts as an allosteric regulator in this case.
Describe how fermentation operates in the absence of Humans: Pyruvate accepts electrons from NADH. This process, called lactic acid
the electron transport chain. fermentation forms lactate and regenerates NAD+. 2 ATP, 2 NAD+ (regenerated).
Yeast: Glycolysis is used to metabolize sugar by enzymatically converting
pyruvate to 2-carbon compound acetaldehyde. 2 CO2, 2 ATP, 2 NAD+
(regenerated).
(2026-2027 Edition)
Final Exam Questions with 100%
Correct Answers and Rationales |
Latest Update | Grade A+
,Name five fundamental characteristics shared by all 1. Cells
living organism. 2. Energy consumption
3. Information
4. Replication
5. Evolutionary adaptation
Describe the two components of cell theory. 1. All living things are made up of cell or cells.
2. Cells come from other cells.
Define energy, and describe the major forms it can take. Energy is the capacity to do work or to supply heat. Potential energy- may be
Understand in what way chemical bonds can be stored. Kinetic energy- may be available in the form of motion. When chemical
considered a form of energy. bonds are formed, energy is released. The internal energy of the system goes
down
Explain, both in mathematical terms and in plain English, ΔG(ibbs free energy) = ΔH (enthalpy) - T ΔS (entropy)
how changes in entropy and potential energy determine
whether or not a reaction is spontaneous. Understand If ΔG is negative (big loss of potential energy, and/or big gain of disorder): the
under what conditions a nonspontaneous reaction can reaction is Exergonic (Exit of energy). SPONTANEOUS
occur.
If ΔG is positive (big gain of potential energy, and/or big loss of disorder): the
reaction is Endergonic (Input of energy). NOT SPONTANEOUS
Explain and give examples of why proteins are essential -Enzyme Catalysis (chemistry)
to cell function. -Cell receptors (signalling and immune response)
-Transport (food uptake, e.g.)
-Support (cell/organism structure)
-Motion (muscles, flagella)
-Regulation (gene expression)
Sketch the basic structure of an amino acid, and Structure: Central carbon atom bonded to an amino group (-NH2), a carboxyl
describe why and how the side chains affect the function group (-COOH), a hydrogen atom and in the 4th position, a side group (R-
and structure of each amino acid. Group). The side chain is the chemical identity to the amino acid and extends out
from the backbone, making it possible for them to interact with each other and
with water. (Visual representation: slide 4)
Sketch a nucleotide, label its three basic parts, and A nucleotide has a sugar or deoxyribose group, a phosphate that is attached on
identify the 2', 3', and 5' carbons. the 5' carbon and an organic nitrogenous base which is attached to the 3'
carbon. Ribose has an -OH on the 2' carbon, Deoxyribose has a H' on the 2'
carbon.
Describe the primary, secondary, tertiary, and quaternary RNA's primary structure consists of a sequence of nitrogen-containing bases that
structures of RNA, and explain in what ways RNA differs contain information in the form of a molecular code. Its secondary structure
from DNA. includes short double helixes and structures called hairpins that holds RNA
strands together. Its tertiary and quaternary structures that fold secondary
structures into complex shapes or hold different RNA strands together. RNA has
Uracil instead of Thymine, it is single stranded, its ribose has an extra -OH group,
and it acts as a transcript of DNA expression. Also, DNA does not have a tertiary
and quaternary structure.
Explain why and how the secondary structure of DNA Complementary base pairing allows each strand of a DNA molecule to be copied
allows organisms to store and copy information. exactly, producing two daughter molecules. DNA's primary structure serves as a
mold or template for the synthesis of a complementary strand and DNA contains
the information required for a copy of itself to be made
Explain why RNA, and not DNA, was probably the first To make a copy of itself, the first living organism had to provide a template that
self-replicating molecule, and describe at least one piece could be copied and catalyze polymerization reactions that would link monomers
of experimental evidence that supports this hypothesis. into a copy of that template. RNA is capable of both.
One experimental evidence is by Wendy Johnston and David Bartel. They found
that ribozymes isolated in each round are copied, the molecules that result are
not identical in terms of their primary sequence because mutations were
introduced during the copying step. By isolating the best enzyme and copying
them in the next round, they continually selected ribozymes that were more
efficient. This was to mimic the process of natural selection
List the features shared by all carbohydrates. A molecule made up of a bunch of carbon, hydrogen, and oxygen. These atoms
are arranged in a few specific ways: they have a carbon atom that's bonded to a
carbonyl group (>C=O), several hydroxyl functional groups (-OH), and many C-H
bonds.
,Sketch several representative monosaccharides, Monosaccharide have a carbonyl group at various locations , several hydroxyl
illustrating three ways in which monosaccharides can functional groups at various locations, and many carbon-hydrogen (C-H) bonds
differ from one another. (energy). Linear form, ring form, alpha vs beta form.
Give examples of the four major functions that Raw materials: Sugars frequently furnish the raw "carbon skeletons" that are
carbohydrates can perform in cells (raw materials, used as a building blocks in the synthesis of important molecules. Amino acids
structure, cell identity, and chemical energy storage). use sugars as a starting point.
Structure: Cellulose and chitin, along with modified polysaccharide
peptidoglycan, are key to structural compounds. They form fibers that give cells
and organisms strength and elasticity.
Cell identity: Enormous number of structurally distinct monosaccharides make it
possible for an enormous number of unique oligosaccharides to exist. As a
result, each cell type and each species can display a unique identity
Chemical energy storage: Kinetic energy in sunlight is converted to chemical
energy stored in bonds of carbohydrates by photosynthesis.
Sketch a phospholipid's molecular structure, and explain Phospholipids have polar ends and nonpolar tails. The hydrophobic tails on the
why phospholipids spontaneously form bilayers in water. phospholipid molecules react with one another, and are repelled by water. The
polar head groups on the phospholipids are hydrophilic and react with water. For
these reasons, the phospholipids organize themselves in such a way as to
maximize the hydrophobic and hydrophilic interactions. The form that
accomplishes this the best is a bilayer.
Predict which way a certain substance will diffuse, given If a solution is hypertonic (the solution surrounding the cell has higher
its concentration on either side of a selectively concentration of solutes) water will rush out of the cell, shrinking it. If a solution is
permeable membrane. hypotonic, (the solution surrounding the cell has less concentration of solutes)
water will rush into the cell, enlarging it. If a solution is isotonic, (the
concentration of solute is the same inside and outside the cell) the water stays as
is.
Describe at least three ways in which membrane 1. Carrier proteins are in the phospholipid bilayer (the membrane) and they
proteins can help substances cross a cell membrane. transport large molecules: glucose and amino acids via the proteins by changing
the shape of them to make them more easy to transport.
2. Channel proteins: Used for ions (as the membrane is polar and so cannot
transport charged particles), and they can be gated and so selected about what
they allow through the protein.
3. Active Transport: Using ATP (energy) to move from a low to a high
concentration of solutes (with other diffusion it is from high to low diffusion) it
transports molecules using carrier proteins, the only difference is the direction
e.g. from a high or a low concentration.
4. Fluid mosaic model: Due to the phospholipids in the bilayer and the fluid like
consistancy of the membrane, small non polar (non charged particles/molecules)
can move through the membrane unaided.
Define the difference between passive transport and -Passive transport- movement is determined by concentration, movement from
active transport, and give examples of each. high to low. Doesn't require any energy. Oxygen and water and get into cells
easily (Diffusion of oxygen into an aerobically respiring cell).
-Active transport- Moving substances across a membrane against their
concentration gradients (high to low). Requires energy (ATP). Example: a cell
uses energy to pump out a substance already present in the extracellular fluid in
concentrations higher than inside the cell
Explain what molecular "zip codes" are and how they Molecular "zip codes" determines where a protein should be delivered. Inside
function. cells, materials are transported to their destinations with the help of molecular
"zip codes."
Describe the structural and functional importance of the This provides a structural framework within the cell, and plays a role in cell
cytoskeleton. division, movement, and transport.
Explain the dynamic nature of the cell. -Lots of chemical reactions occur each second
-Molecules constantly enter and exit across the plasma membrane
-Products move along protein fibers
The cytoskeleton continually grows and shrinks
, Understand the relationship between exergonic and ATP catalyzes endergonic reactions.
endergonic reactions and ATP. Example: ADP + Pi --> ATP
In exergonic reactions, ATP is released.
Example: ATP --> ADP + Pi
Describe the four components of cellular respiration. Part Glycolysis:
1. -starts by using ATP.
-Glucose is phosphorylated to form glucose-6-phosphate.
-An enzyme rearranges this to fructose-6-phosphate.
-A phosphate group is added, making fructose-1,6-biphosphate.
-2 ATP used before any ATP is produced
-NAD+ molecules are reduced
-2 ATP produced
-Final reaction in the sequence produces another 2 ATP
For each molecule of glucose processed, the net yield is 2 NADH, 2 ATP, 2
Pyruvate. Takes place in the cytosol.
Describe the four components of cellular respiration. Part Pyruvate Processing:
2. -Pyruvate reacts with a compound called coenzyme-A (CoA).
-CoA acts as a coenzyme by transferring an acetyl group to a substrate
-Pyruvate reacts with CoA to produce acetyl CoA
NADH produced. Takes place in the cytosol.
Describe the four components of cellular respiration. Part Krebs/Citric Acid Cycle:
3.
-Acetyl-CoA reacts with 4-carbon oxaloacetate to from 6-carbon citric acid
-Two of the 6-carbons of the citric acid leave as CO2
3 NADH, 1 FADH2, 1 ATP. Takes place in the mitochondrial matrix.
Describe the four components of cellular respiration. Part Electron Transport Chain:
4. -NADH and FADH2 is oxidized to NAD+ and FADH
-The electrons released by the NADH and the FADH2 is carried from one
complex to another by molecule ubiquinone and cytochrome c.
-Hydrogen that is also released by the oxidized NADH is pumped from the
matrix, through the complex, to the intermembrane
-Hydrogen protons runs the ATP synthase. The ATP synthase takes ADP and
one inorganic phosphate molecule (Pi). The ATP synthase puts the ADP and the
Pi together to make ATP.
-The electrons are moved from one complex to another, then they are added to 2
hydrogens and 1/2O2 to make H2O.
~29 ATP
Explain how cellular respiration and fermentation are Feedback inhibition. If ATP concentrations are high, the reaction rate is lowered.
regulated. ATP acts as an allosteric regulator in this case.
Describe how fermentation operates in the absence of Humans: Pyruvate accepts electrons from NADH. This process, called lactic acid
the electron transport chain. fermentation forms lactate and regenerates NAD+. 2 ATP, 2 NAD+ (regenerated).
Yeast: Glycolysis is used to metabolize sugar by enzymatically converting
pyruvate to 2-carbon compound acetaldehyde. 2 CO2, 2 ATP, 2 NAD+
(regenerated).
