IB Biology Study Guide with Complete
Solutions
The cell theory (2.1..1.2) - ANSWER-1. The cell is the smallest unit of life
2. All living things are made of cells (or cell products)
3. Cells arise from pre-existing cells
Evidence:
• With the invention of microscopes (Janssen) scientists could see cells (Hooke,
Leeuwenhoek)
• Pasteur demonstrated that cells couldn't grow in sterile conditions (disproved
abiogenesis)
Function of life (2.1.3) - ANSWER-Function of life (2.1.3)
Remember: MRS GREN
Movement
Reproduction
Sensitivity (to stimuli)
Growth
Respiration
Excretion
Nutrition
Cell size (2.1.4 - 2.1.6) - ANSWER-• The rate of metabolism (e.g. cell respiration) is a
function of a cell's volume
• The rate at which material is exchanged (needed for metabolism) is a function of a
cell's surface area • When a cell grows, volume grows quicker than surface area and
the cell must divide or die
• Many cells contains structures (e.g. microvilli) to increase their SA:Vol ratio
Calculating cell sizes:
• Magnification = Size of image (magnified) ÷ Actual size of object
Relative sizes:
• Eukaryote (10 - 100μm) > Organelle (~10μm) > Bacteria (1 - 5μm) > virus (100nm) >
membrane (7.5nm)
Differential gene expression (2.1..1.8) - ANSWER-• Differentiation is the process by
which newly-formed cells specialize as they mature
• Cells in multi-cellular organisms share identical genomes but differ in gene expression
• Chemical signals lead to differential gene expression and thus specialization of cells
• The combination of different cell types can give rise to emergent properties
,Stem cells (2.1..1..4..4.13) - ANSWER-• Stem cells retain the capacity to
divide and differentiate along different pathways
• Therapeutic cloning can be used to regenerate skin cells in burns victims
Reproductive Cloning Steps: somatic cell -> nucleus -> fusion of cell & nucleus -> stem
cells -> surrogate
Therapeutic Cloning Steps: egg cell -> enucleated cell -> fusion of both cells -> stem
cells -> surrogate
Arguments For Therapeutic Cloning:
• May be used to cure diseases (e.g. diabetes)
• Stem cell research may promote future discoveries
• Cells cultured when embryos lack nervous system
Arguments Against Therapeutic Cloning:
• Involves creation and destruction of embryos
• Rapidly dividing cells may become cancerous
• At more cost, other technologies fulfill same role
Know how to draw Prokaryotic & Eukaryotic Cell - ANSWER-Reference diagrams from
Bioninja
Compare pro- / eukaryotes (2.3.4) - ANSWER-Remember: DR MARIO:
DNA (naked vs histones)
Ribosomes (70S vs 80S)
Morphology (unicellular vs multicellular)
Average Size (1-5 μm vs 10-100 μm) Reproduction (binary fission vs mitosis)
Internal Structures (membranous organelles)
Other features (plasmids, ploidy, nucleus, etc)
Compare plant / animal cells (2.3.5) - ANSWER-Remember: Clever Vampires Can
Confront Sunlight:
Cell Wall (cellulose vs none)
Vacuole (large & central vs small & temporary)
Chloroplast (present vs absent) Centrosome (no centrioles vs centrioles)
Sugar Storage (starch vs glycogen)
State how bacteria divide (2.2.4) - ANSWER-State how bacteria divide (2.2.4) Bacteria
divide by binary fission
Outline 2 extracellular components (2.3.6) - ANSWER-Cell Wall (plants) - maintain
shape, infection barrier
ECM (animals) - anchorage, segregation
Label diagram of a Membrane - ANSWER-Reference diagram from Bioninja
,Explain how properties of phospholipids maintain membrane structure (2.4.2) -
ANSWER-• Structure of phospholipid (hydrophilic/polar head & hydrophobic/non-polar
tails)
• Arrangement in bilayer (hydrophobic tails face inwards; hydrophilic heads face
surrounding fluid)
• Properties of membrane (hydrophobic interactions, fluidity, saturated vs unsaturated
fatty acids)
Functions of membrane proteins (2.4.3) - ANSWER-Remember: TRACIE:
Transport (active vs facilitated diffusion)
Receptors (e.g. for hormones & neurotransmitters)
Adhesion (attachment sites for ECM) Cell Recognition (MHC molecules; HLA antigens)
Intercellular Joining (e.g. tight junctions)
Enzymatic Activity (e.g. ATP synthase)
Define diffusion & osmosis (2.4.4) - ANSWER-Diffusion: Net movement of molecules
from a region of high to low concentration, until equilibrium is reached
Osmosis: Net movement of water molecules across a semi-permeable barrier from a
region of low solute to high solute concentration, until equilibrium is reached
Explain passive transport (2.4.5) - ANSWER-Remember: Along gradient, no ATP
Simple: Small or lipophilic molecules cross freely Examples: O2, CO2, H2O, steroids
Facilitated: Larger, polar substances cross via protein channels (interior linings are
polar) Examples: Ions, glucose, sucrose
Explain active transport (2.4.6) - ANSWER-Remember: Against gradient, uses ATP
• Molecule binds to surface of protein pump
• Hydrolysis of ATP causes a conformational
change in protein pump
• Molecule translocated to interior surface
Examples: Na+/K+ pump
Explain vesicle transport (2.4.7) - ANSWER-Polypeptides destined for secretion are
embedded to Rough ER surface -> Polypeptides transported to Golgi Apparatus via
vesicles -> transported to plasma membrane via another vesicle where contents are
released (exocytosis)
Describe membrane fluidity (2.4.8) - ANSWER-• Change shape (membrane is
amorphous)
• Break and reform (weak hydrophobic forces)
• Cytosis (endocytosis vs exocytosis)
Outline stages in the cell cycle (2.5.1) - ANSWER-Interphase
, • G1 (before DNA replication: cell growth & organelle duplication)
• S (DNA replication)
• G2 (after DNA replication: final growth & DNA 'proof-reading')
Mitosis
• Nuclear division (prophase, metaphase, anaphase, telophase)
Cytokinesis
• Cytoplasmic division (cell creates an actin furrow and divides)
Functions of interphase (2.5.3) - ANSWER-Remember: PAID
Protein synthesis (transcription/translation)
Aerobic respiration (ATP formation) Increase organelles (mitochondria/chloroplast)
DNA replication (in S phase)
Explain genetic duplication (2.5.5) - ANSWER-Remember: Mitosis = genetically
identical
• In S phase, DNA is copied so that chromosomes are made of identical sister
chromatids
• Conservation of base sequence is achieved by complementary base pairing
• In anaphase, identical sister chromatids split apart (becoming separate chromosomes)
• In telophase, nuclei reform around separated chromosomes, resulting in the formation
of genetically identical nuclei
Describe the events that occur in the four phases of mitosis (2.5.4) - ANSWER-1.
Prophase
• DNA supercoils (chromatin → chromosome)
• Nuclear membrane dissolves
• Centrosomes move to opposite poles
• Centrioles start making spindle fibres
2. Metaphase
• Spindle fibres connect to centromere
• Chromosomes line up along equator
3. Anaphase
• Spindle fibres contract
• Sister chromatid chromosomes split into genetically identical single chromatid
chromosomes
• Chromosomes move to opposite poles
4. Telophase
• DNA decondenses (chromosome → chromatin)
• Nuclear membranes reform around chromatin
State the roles of mitosis (2.5.6) - ANSWER-Remember: GATE
Growth
Asexual reproduction
Tissue repair
Embryonic development
Solutions
The cell theory (2.1..1.2) - ANSWER-1. The cell is the smallest unit of life
2. All living things are made of cells (or cell products)
3. Cells arise from pre-existing cells
Evidence:
• With the invention of microscopes (Janssen) scientists could see cells (Hooke,
Leeuwenhoek)
• Pasteur demonstrated that cells couldn't grow in sterile conditions (disproved
abiogenesis)
Function of life (2.1.3) - ANSWER-Function of life (2.1.3)
Remember: MRS GREN
Movement
Reproduction
Sensitivity (to stimuli)
Growth
Respiration
Excretion
Nutrition
Cell size (2.1.4 - 2.1.6) - ANSWER-• The rate of metabolism (e.g. cell respiration) is a
function of a cell's volume
• The rate at which material is exchanged (needed for metabolism) is a function of a
cell's surface area • When a cell grows, volume grows quicker than surface area and
the cell must divide or die
• Many cells contains structures (e.g. microvilli) to increase their SA:Vol ratio
Calculating cell sizes:
• Magnification = Size of image (magnified) ÷ Actual size of object
Relative sizes:
• Eukaryote (10 - 100μm) > Organelle (~10μm) > Bacteria (1 - 5μm) > virus (100nm) >
membrane (7.5nm)
Differential gene expression (2.1..1.8) - ANSWER-• Differentiation is the process by
which newly-formed cells specialize as they mature
• Cells in multi-cellular organisms share identical genomes but differ in gene expression
• Chemical signals lead to differential gene expression and thus specialization of cells
• The combination of different cell types can give rise to emergent properties
,Stem cells (2.1..1..4..4.13) - ANSWER-• Stem cells retain the capacity to
divide and differentiate along different pathways
• Therapeutic cloning can be used to regenerate skin cells in burns victims
Reproductive Cloning Steps: somatic cell -> nucleus -> fusion of cell & nucleus -> stem
cells -> surrogate
Therapeutic Cloning Steps: egg cell -> enucleated cell -> fusion of both cells -> stem
cells -> surrogate
Arguments For Therapeutic Cloning:
• May be used to cure diseases (e.g. diabetes)
• Stem cell research may promote future discoveries
• Cells cultured when embryos lack nervous system
Arguments Against Therapeutic Cloning:
• Involves creation and destruction of embryos
• Rapidly dividing cells may become cancerous
• At more cost, other technologies fulfill same role
Know how to draw Prokaryotic & Eukaryotic Cell - ANSWER-Reference diagrams from
Bioninja
Compare pro- / eukaryotes (2.3.4) - ANSWER-Remember: DR MARIO:
DNA (naked vs histones)
Ribosomes (70S vs 80S)
Morphology (unicellular vs multicellular)
Average Size (1-5 μm vs 10-100 μm) Reproduction (binary fission vs mitosis)
Internal Structures (membranous organelles)
Other features (plasmids, ploidy, nucleus, etc)
Compare plant / animal cells (2.3.5) - ANSWER-Remember: Clever Vampires Can
Confront Sunlight:
Cell Wall (cellulose vs none)
Vacuole (large & central vs small & temporary)
Chloroplast (present vs absent) Centrosome (no centrioles vs centrioles)
Sugar Storage (starch vs glycogen)
State how bacteria divide (2.2.4) - ANSWER-State how bacteria divide (2.2.4) Bacteria
divide by binary fission
Outline 2 extracellular components (2.3.6) - ANSWER-Cell Wall (plants) - maintain
shape, infection barrier
ECM (animals) - anchorage, segregation
Label diagram of a Membrane - ANSWER-Reference diagram from Bioninja
,Explain how properties of phospholipids maintain membrane structure (2.4.2) -
ANSWER-• Structure of phospholipid (hydrophilic/polar head & hydrophobic/non-polar
tails)
• Arrangement in bilayer (hydrophobic tails face inwards; hydrophilic heads face
surrounding fluid)
• Properties of membrane (hydrophobic interactions, fluidity, saturated vs unsaturated
fatty acids)
Functions of membrane proteins (2.4.3) - ANSWER-Remember: TRACIE:
Transport (active vs facilitated diffusion)
Receptors (e.g. for hormones & neurotransmitters)
Adhesion (attachment sites for ECM) Cell Recognition (MHC molecules; HLA antigens)
Intercellular Joining (e.g. tight junctions)
Enzymatic Activity (e.g. ATP synthase)
Define diffusion & osmosis (2.4.4) - ANSWER-Diffusion: Net movement of molecules
from a region of high to low concentration, until equilibrium is reached
Osmosis: Net movement of water molecules across a semi-permeable barrier from a
region of low solute to high solute concentration, until equilibrium is reached
Explain passive transport (2.4.5) - ANSWER-Remember: Along gradient, no ATP
Simple: Small or lipophilic molecules cross freely Examples: O2, CO2, H2O, steroids
Facilitated: Larger, polar substances cross via protein channels (interior linings are
polar) Examples: Ions, glucose, sucrose
Explain active transport (2.4.6) - ANSWER-Remember: Against gradient, uses ATP
• Molecule binds to surface of protein pump
• Hydrolysis of ATP causes a conformational
change in protein pump
• Molecule translocated to interior surface
Examples: Na+/K+ pump
Explain vesicle transport (2.4.7) - ANSWER-Polypeptides destined for secretion are
embedded to Rough ER surface -> Polypeptides transported to Golgi Apparatus via
vesicles -> transported to plasma membrane via another vesicle where contents are
released (exocytosis)
Describe membrane fluidity (2.4.8) - ANSWER-• Change shape (membrane is
amorphous)
• Break and reform (weak hydrophobic forces)
• Cytosis (endocytosis vs exocytosis)
Outline stages in the cell cycle (2.5.1) - ANSWER-Interphase
, • G1 (before DNA replication: cell growth & organelle duplication)
• S (DNA replication)
• G2 (after DNA replication: final growth & DNA 'proof-reading')
Mitosis
• Nuclear division (prophase, metaphase, anaphase, telophase)
Cytokinesis
• Cytoplasmic division (cell creates an actin furrow and divides)
Functions of interphase (2.5.3) - ANSWER-Remember: PAID
Protein synthesis (transcription/translation)
Aerobic respiration (ATP formation) Increase organelles (mitochondria/chloroplast)
DNA replication (in S phase)
Explain genetic duplication (2.5.5) - ANSWER-Remember: Mitosis = genetically
identical
• In S phase, DNA is copied so that chromosomes are made of identical sister
chromatids
• Conservation of base sequence is achieved by complementary base pairing
• In anaphase, identical sister chromatids split apart (becoming separate chromosomes)
• In telophase, nuclei reform around separated chromosomes, resulting in the formation
of genetically identical nuclei
Describe the events that occur in the four phases of mitosis (2.5.4) - ANSWER-1.
Prophase
• DNA supercoils (chromatin → chromosome)
• Nuclear membrane dissolves
• Centrosomes move to opposite poles
• Centrioles start making spindle fibres
2. Metaphase
• Spindle fibres connect to centromere
• Chromosomes line up along equator
3. Anaphase
• Spindle fibres contract
• Sister chromatid chromosomes split into genetically identical single chromatid
chromosomes
• Chromosomes move to opposite poles
4. Telophase
• DNA decondenses (chromosome → chromatin)
• Nuclear membranes reform around chromatin
State the roles of mitosis (2.5.6) - ANSWER-Remember: GATE
Growth
Asexual reproduction
Tissue repair
Embryonic development
