Chapter 1 - Kaplan MCAT Biology Review

2025-2026

cell theory

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 info in the form of DNA, this genetic material is passed from parent to daughter cell

viruses contain genetic material but

cannot reproduce on their own

prokaryotic organisms

single celled

eukaryotic organisms

unicellular or multicellular

prokaryotic cells do not contain

-nucleus

-membrane bound organelles

eukaryotic cells have a

true nucleus enclosed in membrane

each cell has a membrane enclosing a semifluid ____ in which the organelles are suspended

cytosol

membrane of eukaryotic cells consists of

phospholipid bilayer

the phospholipid bilayer

-surfaces are hydrophilic (for aqueous environment)

-inner portion is hydrophobic (selective barrier)

cytosol allows for

diffusion of molecules throughout the cell

genetic material is encoded in ___ which is organized into _____

DNA, chromosomes

mitosis

-common to all eukaryotes

-daughter cells contain same number of chromosomes as parent cell

meiosis

-occurs in eukaryotic organisms that reproduce sexually

-produces gametes that have half as many chromosomes as the other cells in the organism

-each gamete is unique bc parent cells dna shuffles before division

binary fission

-how prokaryotic cells replicate

-requires replication of cells chromosomes

nucleus

has all genetic material needed for replication

nucleus is surrounded by

nuclear membrane or envelope

nuclear membrane or envelope

a double membrane that has a nuclear environment separate and distinct from the cytoplasm

nuclear pores

-in the nuclear membrane

-allow selective 2-way exchange of material between the cytoplasm and nucleus

DNA has coding regions called

genes

linear DNA is wound around organizing proteins known as ___, and then further wound into linear strands called ____

histones, chromosomes

nucleolus

-subsection of nucleus

-where ribosomal RNA (rRNA) is synthesized

mitochondria outer membrane

barrier between cytosol and inner environment of mitochondrion

mitochondria inner membrane

contains the molecules and enzymes of electron transport chain

mitochondria inner membrane is arranged into unfolding called

cristae (increase surface area available for electron transport chain enzymes)

space between inner and outer membrane of mitochondria is called

intermembrane space

space inside inner membrane of mitochondria is called the

mitochondrial matrix

the pumping of protons from the _____ to the _____ establishes the proton-motive force

mitochondrial matrix, intermembrane space

proton-motive force

force that promotes movement of protons across membranes down the electrochemical potential

protons in proton-motive force

flow through ATP synthase to generate ATP during oxidative phosphorylation

mitochondria are semi-autonomous because they

contain some of their own genes and replicate independently of the nucleus via binary fission

the transmission of genetic material independent of the nucleus is called

cytoplasmic or extranuclear inheritance

mitochondria releases enzymes from the _____ to kickstart apoptosis

electron transport chain

lysosomes

-membrane bound

-contain hydrolysis enzymes that can break down substrates (including substances ingested by endocytosis and cellular waste products)

lysosomes function alongside ___

endosomes

endosomes

transport, package, and sort cell material traveling to and from the membrane

endosomes can transport materials to the ____, the ____, or to the _______ for degradation

transgolgi, cell membrane, lysosomal pathways

lysosomes releasing hydrolytic enzymes can result in a process known as

autolysis (resulting in apoptosis?)

endoplasmic reticulum (ER)

-series of interconnected membranes

-borders nuclear envelope

rough ER (RER)

studded with ribosomes that permit translation of proteins destined for secretion into its lumen

smooth ER (SER)

-no ribosomes

-used for lipid synthesis (phospholipids in cell membrane)

-used for detoxification of certain drugs and poisons

-transports proteins from the RER to the golgi apparatus

golgi apparatus

-stacked membrane-bound sacs

-receives materials in vesicles from ER

-may modify cellular products (by adding carbohydrates, phosphates, or sulfates, or signal sequences)

signal sequences

direct product to specific location

after golgi modifies and sorts, products are

repackaged in vesicles, and then directed to correct location

if product is to be secreted, _____ merges with _____, and its contents are released via endocytosis

secretory vesicles, cell membrane

peroxisomes

-contain hydrogen peroxide

-breaks down very long chain fatty acids via beta-oxidation

-synthesis of phospholipids and contain some enzymes involved in the pentose phosphate pathway

cytoskeleton

-provides structure to cell and maintain shape

-provides a conduit for the transport of materials

3 components of cytoskeleton

1. microfilaments

2. microtubules

3. intermediate filaments

microfilaments

-made of actin

-plays role in cytokinesis

cytokinesis

division of materials between daughter cells

actin filaments are resistant to ____ and ____

compression, fracture

actin filaments can use ATP to generate force for movement by interacting with ____

myosin

during mitosis, the _____ is formed from microfilaments (during cytokinesis)

cleavage furrow

steps of cytokinesis

1. cleavage furrow formed

2. organizes as ring at site of division

3. as actin filaments contract, ring becomes smaller

4. pinches off connection

microtubules

-hollow polymers of tubulin proteins

-provide pathways for kinesin and dynein (to carry vesicles)

cilia

projections from a cell involved in movement of materials along surface of cell

flagella

structures involved in movement of cell itself

cilia and flagella are composed of

9+2

-9 pairs of microtubules forming outer ring

-2 microtubules in center

9+2 structure is only seen in

eukaryotic organelles of motility

centrioles are found in

centrosomes

centrioles

organizing centers for microtubules

centrioles are structured as

9 triplets of microtubules w a hollow center

during mitosis, centrioles…

migrate to opposite poles of dividing cell and organize mitotic spindle

the microtubules emanating from the centrioles attach to

the chromosomes via complexes called kinetochores and pull apart sister chromatids

intermediate filaments

-filamentous proteins (keratin, desmin, vimentin, lamins)

-cell-cell adhesion

-maintenance of integrity of cytoskeleton

-anchor other organelles

intermediate filaments can withstand

tension

types of tissue

-epithelial

-connective

-muscle

-nervous

epithelial tissue

-covers body and lines its cavities

-provides protection

-sometimes involved in absorption, secretion, and sensation

epithelial cells are tightly joined to

each other and to basement membrane

basement membrane

underlying layer of connective tissue

epithelial cells constitute the

parenchyma

parenchyma

functional parts of organ

epithelial cells are polarized:

-one side faces a lumen or outside world

-other side interacts with underlying blood vessels and structural cells

lumen

hollow inside of an organ or tube

simple epithelia

one layer of cells

stratified epithelia

multiple layers of cells

pseudostratified epithelia

one layer of cells but looks like multiple layers

cuboidal cells

cube shaped

columnar cells

long and thin

squamous cells

flat and scale-like

connective tissue

-supports the body and its framework

-for epithelial cells to carry out their functions

connective tissue is main contributor to the

stroma

stroma

support structure

examples of connective tissue

bone, cartilage, tendons, ligaments, adipose tissue, blood

most cells in connective tissues produce and secrete materials such as

collagen and elastin (to form extracellular matrix)

prokaryotes contain genetic material in

single circular molecule of DNA in nucleoid region

prokaryotes carry out electron transport chain using

the cell membrane

prokaryotic ribosomes are (smaller/larger) than eukaryotic ribosomes

smaller

3 overarching domains of life

-eukarya

-archaea (prokaryote)

-bacteria (prokaryote)

archaea

-extremophiles

-often use chemical sources of energy

extremophiles live in harsh environments such as

-high temp

-high salinity

-no light

chemosynthesis

getting energy from chemical sources

photosynthesis

get energy from light

archaea similarities to eukaryotes

-start translation with methionine

-similar RNA polymerase

-histones

archaea similarities to bacteria

-single circular chromosome

-divide by binary fission or budding

bacteria’s relationship w humans

-mutualistic symbiosis

-pathogenesis

bacteria shape classifications

-cocci

-bacilli

-spirilli

cocci

spherical bacteria

bacilli

rod-shaped bacteria

spirilli

spiral-shaped bacteria

bacteria metabolic processes classifications

-obligate aerobes

-obligate anaerobes

-facultative anaerobes

-aerotolerant anaerobes