MCAT Biology Exam Practice
2026 – Verified Questions,
Detailed Explanations & Study
Guide for Pre-Med Success
Cell Theory - ANSWER-Four Tenets:
1. All living things are composed of cells
2. The cell is the basic functional unit of life
3. Cells arise only from preexisting cells
4. Cells carry genetic information in the form of DNA
Eukaryotic Cells - ANSWER-Contain a true nucleus enclosed in a membrane.
Prokaryotic Cells - ANSWER-Do not contain a nucleus.
Organelles - ANSWER-Suspended in semifluid cytosol. In eukaryotic cells they are
membrane bound, allowing for compartmentalization of functions. The
membranes are made of a phospholipid bilayer, surfaces are hydrophilic, they
interact with the environment.
,Cytosol - ANSWER-Allows for diffusion of molecules throughout the cell.
Nucleus - ANSWER-Genetic material is encoded in DNA, organized in
chromosomes. This DNA provides all the genetic material needed for replication
of the cell. It is surrounded by the nuclear membrane or envelope, which forms a
double membrane. Nuclear pores allow for selective exchange of material
between cytoplasm and the nucleus.
Genetic Material of the Nucleus - ANSWER-DNA contains coding regions called
genes. Linear DNA is wound around organizing proteins known as histones, and
further wound into chromosomes.
Nuclear Membrane - ANSWER-Contains nuclear pores that allow for selective 2-
way exchange of material between the cytoplasm and the nucleolus
Nucleolus - ANSWER--Subsection of the nucleus
-Where ribosomal RNA is synthesized
-The darker spot that is 25% of the nucleus
Mitochondria - ANSWER-Power plant of the cell. Two layers, inner and outer
membrane. The outer membrane is a barrier between the cytosol and the inner
environment of the mitochondria. The inner membrane, made up of infoldings
called cristae, contains the molecules and enzymes necessary for the electron
transport chain. The intermembrane space separates them, creating a matrix
between them.
,The pumping of protons from the matrix to the intermembrane space creates a
proton-motive force that generates ATP via protons flowing through and turning
ATP synthase (oxidative phosphorylation). The mitochondria is semiautonomous,
meaning they replicate independently of the the nucleus via binary fission.
They can kill the cell via release of enzymes that aid in apoptosis.
Lysosomes - ANSWER-Membrane-bound structures containing hydrolytic enzymes
that are capable of breaking down many different substrates, including those
ingested by endocytosis and cellular waste products.
The enzymes are sequestered to protect the cell, releasing these enzymes causes
autolysis, resulting in apoptosis...in this case, the released enzymes directly lead
to cell degradation.
Rough Endoplasmic Reticulum (RER) - ANSWER-Interconnected membranes that
are actually contiguous with the nuclear envelope. It is folding into complex
structures with a central lumen. The Rough ER is studded with ribosomes that
permit translation of proteins destined for secretion into the lumen.
Golgi Apparatus - ANSWER-Stacked membrane-bound sacs that are transferred
from the ER via vesicles. The Golgi modifies the products via addition of various
groups. It modifies cellular products thought the introduction of signal sequences,
which help direct the delivery of product to a specific cellular location. Can also
send to lysosomes for degredation
Exocytosis - ANSWER-Used in secretion, when the secretory vesicle merges with
the cell membrane and its contents.
, Peroxisomes - ANSWER-Contain hydrogen peroxide. It breaks down long chain
fatty acids via beta oxidation. They help in the synthesis of phospholipids.
Cytoskeleton - ANSWER-Provides structure to the cell and helps it to maintain its
shape. It also provides a conduit for transport of material around the cell.
Microfilaments - ANSWER-Solid polymerized rods of actin organized into bundles
and networks that are resistant to compression and fracture. They assist in
cytokinesis and cleavage furrow. Present in muscle
Actin - ANSWER-Subunit of microfilaments, used with ATP to generate force for
movement by interacting with myosin for muscle contraction.
Microtubules - ANSWER-Hollow polymers of tubulin proteins that provide a
primary pathway along which motor proteins like kinesin and dynein carry
vesicles. Makes cilia and flagella. Also makes centrioles
Cilia - ANSWER-Projections of the cell that are primarily involved in movement of
materials along the surface of a cell. They are made of microtubules and an
example is respiratory cilia.
Flagella - ANSWER-Structures involved in the movement of the cell itself, such as
the movement of sperm cells through the reproductive tract.
2026 – Verified Questions,
Detailed Explanations & Study
Guide for Pre-Med Success
Cell Theory - ANSWER-Four Tenets:
1. All living things are composed of cells
2. The cell is the basic functional unit of life
3. Cells arise only from preexisting cells
4. Cells carry genetic information in the form of DNA
Eukaryotic Cells - ANSWER-Contain a true nucleus enclosed in a membrane.
Prokaryotic Cells - ANSWER-Do not contain a nucleus.
Organelles - ANSWER-Suspended in semifluid cytosol. In eukaryotic cells they are
membrane bound, allowing for compartmentalization of functions. The
membranes are made of a phospholipid bilayer, surfaces are hydrophilic, they
interact with the environment.
,Cytosol - ANSWER-Allows for diffusion of molecules throughout the cell.
Nucleus - ANSWER-Genetic material is encoded in DNA, organized in
chromosomes. This DNA provides all the genetic material needed for replication
of the cell. It is surrounded by the nuclear membrane or envelope, which forms a
double membrane. Nuclear pores allow for selective exchange of material
between cytoplasm and the nucleus.
Genetic Material of the Nucleus - ANSWER-DNA contains coding regions called
genes. Linear DNA is wound around organizing proteins known as histones, and
further wound into chromosomes.
Nuclear Membrane - ANSWER-Contains nuclear pores that allow for selective 2-
way exchange of material between the cytoplasm and the nucleolus
Nucleolus - ANSWER--Subsection of the nucleus
-Where ribosomal RNA is synthesized
-The darker spot that is 25% of the nucleus
Mitochondria - ANSWER-Power plant of the cell. Two layers, inner and outer
membrane. The outer membrane is a barrier between the cytosol and the inner
environment of the mitochondria. The inner membrane, made up of infoldings
called cristae, contains the molecules and enzymes necessary for the electron
transport chain. The intermembrane space separates them, creating a matrix
between them.
,The pumping of protons from the matrix to the intermembrane space creates a
proton-motive force that generates ATP via protons flowing through and turning
ATP synthase (oxidative phosphorylation). The mitochondria is semiautonomous,
meaning they replicate independently of the the nucleus via binary fission.
They can kill the cell via release of enzymes that aid in apoptosis.
Lysosomes - ANSWER-Membrane-bound structures containing hydrolytic enzymes
that are capable of breaking down many different substrates, including those
ingested by endocytosis and cellular waste products.
The enzymes are sequestered to protect the cell, releasing these enzymes causes
autolysis, resulting in apoptosis...in this case, the released enzymes directly lead
to cell degradation.
Rough Endoplasmic Reticulum (RER) - ANSWER-Interconnected membranes that
are actually contiguous with the nuclear envelope. It is folding into complex
structures with a central lumen. The Rough ER is studded with ribosomes that
permit translation of proteins destined for secretion into the lumen.
Golgi Apparatus - ANSWER-Stacked membrane-bound sacs that are transferred
from the ER via vesicles. The Golgi modifies the products via addition of various
groups. It modifies cellular products thought the introduction of signal sequences,
which help direct the delivery of product to a specific cellular location. Can also
send to lysosomes for degredation
Exocytosis - ANSWER-Used in secretion, when the secretory vesicle merges with
the cell membrane and its contents.
, Peroxisomes - ANSWER-Contain hydrogen peroxide. It breaks down long chain
fatty acids via beta oxidation. They help in the synthesis of phospholipids.
Cytoskeleton - ANSWER-Provides structure to the cell and helps it to maintain its
shape. It also provides a conduit for transport of material around the cell.
Microfilaments - ANSWER-Solid polymerized rods of actin organized into bundles
and networks that are resistant to compression and fracture. They assist in
cytokinesis and cleavage furrow. Present in muscle
Actin - ANSWER-Subunit of microfilaments, used with ATP to generate force for
movement by interacting with myosin for muscle contraction.
Microtubules - ANSWER-Hollow polymers of tubulin proteins that provide a
primary pathway along which motor proteins like kinesin and dynein carry
vesicles. Makes cilia and flagella. Also makes centrioles
Cilia - ANSWER-Projections of the cell that are primarily involved in movement of
materials along the surface of a cell. They are made of microtubules and an
example is respiratory cilia.
Flagella - ANSWER-Structures involved in the movement of the cell itself, such as
the movement of sperm cells through the reproductive tract.
