IB Biology HL Essay Questions
UNIT 1: CELL BIOLOGY 3
1.1: INTRODUCTION TO CELLS 3
1.2: ULTRASTRUCTURE OF CELLS 4
1.3: MEMBRANE STRUCTURE 6
1.4: MEMBRANE TRANSPORT 7
1.6: CELL DIVISION 8
UNIT 2: MOLECULAR BIOLOGY 9
2.1: MOLECULES TO METABOLISM 9
2.2: WATER 10
2.3: CARBOHYDRATES AND LIPIDS 10
2.4: PROTEINS 11
2.5: ENZYMES 12
2.6: STRUCTURE OF DNA AND RNA 12
2.8: CELL RESPIRATION 14
2.9: PHOTOSYNTHESIS 14
UNIT 3: GENETICS 16
3.1: GENES 16
3.2: CHROMOSOMES 16
3.3: MEIOSIS 17
3.4: INHERITANCE 17
UNIT 4: ECOLOGY 19
4.1: SPECIES, COMMUNITIES AND ECOSYSTEMS 19
4.2: ENERGY FLOW 19
4.3: CARBON CYCLING 20
4.4: GREENHOUSE EFFECT 20
UNIT 5: EVOLUTION AND BIODIVERSITY 21
5.1: EVIDENCE FOR EVOLUTION 21
4.2: NATURAL SELECTION 22
5.3: CLASSIFICATION OF BIODIVERSITY 23
UNIT 6: HUMAN PHYSIOLOGY 26
6.1: STRUCTURE OF THE DIGESTIVE SYSTEM 26
6.2: THE BLOOD SYSTEM 28
6.3: DEFENSE AGAINST INFECTIOUS DISEASES 30
6.5: NEURONS AND SYNAPSES 32
6.6: HORMONES, HOMEOSTASIS AND REPRODUCTION 35
UNIT 7: NUCLEIC ACIDS 39
7.1 DNA STRUCTURE AND REPLICATION 39
7.1: TRANSCRIPTION AND GENE EXPRESSION 41
7.3: TRANSLATION 41
UNIT 8: METABOLISM, CELL RESPIRATION AND PHOTOSYNTHESIS 43
,8.1: METABOLISM 43
8.2: CELL RESPIRATION 44
8.3: PHOTOSYNTHESIS 47
UNIT 9: PLANT BIOLOGY 51
9.1: TRANSPORT IN THE XYLEM OF PLANTS 51
9.2: TRANSPORT IN THE PHLOEM OF PLANTS 54
9.3: GROWTH IN PLANTS 54
9.4: REPRODUCTION IN PLANTS 54
UNIT 10: GENETICS AND EVOLUTION 56
10.1: MEIOSIS 56
10.2: INHERITANCE 57
10.3: GENE POOLS AND SPECIATION 58
UNIT 11: ANIMAL PHYSIOLOGY 60
11.1: ANTIBODY PRODUCTION AND VACCINATION 60
11.2: MOVEMENT 62
11.3: THE KIDNEY AND OSMOREGULATION 64
11.4: SEXUAL REPRODUCTION 66
Notes:
2
,Unit 1: Cell Biology
1.1: Introduction to cells
1. Discuss possible exceptions to cell theory. 4 marks
▪ skeletal muscle fibers are larger/have many nuclei/are not typical cells
▪ fungal hyphae are (sometimes) not divided up into individual cells
▪ unicellular organisms can be considered acellular
▪ because they are larger than a typical cell/carry out all functions of life
▪ some tissues/organs contain large amounts of extracellular material
▪ e.g. vitreous humor of eye/ mineral deposits in bone/ xylem in trees/other
example
▪ statement of cell theory/all living things/most tissues are composed entirely of true
cells
2. Eukaryotic cells have intracellular and extracellular components. State the
functions of one named extracellular component. 4 marks
name of component: 1 max
▪ e.g. plant cell wall/cellulose/interstitial
▪ matrix/basement membrane/glycoprotein/bone matrix;
functions: 3 max
EITHER
▪ e.g. (plant cell wall) strengthens/supports the cell/plant (against gravity);
▪ prevents the entry of pathogens;
▪ maintains the shape of plant cells;
▪ allows turgor pressure/high pressure to develop inside the cell;
▪ prevents excessive entry of water to the cell;
OR
▪ helps cells to stick together/adhere;
▪ needed to hold cells/tissues together / example of cells/tissues holding together;
▪ forms interstitial matrix / forms basement membrane to support single layers of
cells;
▪ e.g. around a blood capillary;
▪ forms (part of the) filtration membrane in the glomerulus;
3. Explain how the surface are to volume ratio influences cell sizes. 3 marks
▪ small cells have larger ratio (than larger cells)/ratio decreases as size increases
▪ surface area/membrane must be large enough to absorb
nutrients/oxygen/substances needed
▪ surface area/membrane must be large enough to excrete/pass out waste products
▪ need for materials is determined by (cell) volume
▪ cell size is limited (by SA/Volume ratio)/cells divide when they reach a certain size
▪ reference to diffusion across/through membrane/surface area
4. Outline differentiation of cells in a multicellular organism. 4 marks
▪ differentiation is development in different/specific ways
▪ cells carry out specialized functions/become specialized
3
, ▪ example of a differentiated cell in a multicellular organism
▪ cells have all genes/could develop in any way
▪ some genes are switched on/expressed but not others
▪ position/hormones/cell-to-cell signals/chemicals determine how a cell develops
▪ a group of differentiated cells is a tissue
5. Describe the importance of stem cells in differentiation. 3 marks
▪ stem cells are undifferentiated cells;
▪ embryo cells are stem cells;
▪ stem cells can differentiate in many/all ways / are pluripotent/totipotent;
▪ differentiation involves expressing some genes but not others;
▪ stem cells can be used to repair/replace tissues/heal wounds;
1.2: Ultrastructure of Cells
6. Draw a labeled diagram to show
the ultrastructure of Escherichia
coli. 6 marks
Award 1 for each structure clearly drawn
and correctly labeled.
▪ cell wall – with some thickness;
▪ plasma membrane – shown as
single line or very thin;
▪ cytoplasm;
▪ pilus/pili – shown as single lines;
▪ flagellum/flagella – shown as
thicker and longer structures than
pili and embedded in cell wall;
▪ 70S ribosomes;
▪ nucleoid / naked DNA;
▪ approximate width 0.5 μm /
approximate length 2.0 μm;
Award 4 max if the bacterium drawn does
not have the shape of a bacillum (rounded-
corner rectangle with length approximately
twice its width). Award 4 max if any
eukaryotic structures included.
7. Draw a labelled diagram to show the organelles which are found in the
cytoplasm of plant cells. 6
marks
▪ rough endoplasmic
reticulum
▪ free ribosomes
▪ Golgi apparatus
▪ mitochondrion
▪ chloroplast
▪ vacuole
▪ nucleus
▪ lysosome
▪ smooth endoplasmic
reticulum
4
UNIT 1: CELL BIOLOGY 3
1.1: INTRODUCTION TO CELLS 3
1.2: ULTRASTRUCTURE OF CELLS 4
1.3: MEMBRANE STRUCTURE 6
1.4: MEMBRANE TRANSPORT 7
1.6: CELL DIVISION 8
UNIT 2: MOLECULAR BIOLOGY 9
2.1: MOLECULES TO METABOLISM 9
2.2: WATER 10
2.3: CARBOHYDRATES AND LIPIDS 10
2.4: PROTEINS 11
2.5: ENZYMES 12
2.6: STRUCTURE OF DNA AND RNA 12
2.8: CELL RESPIRATION 14
2.9: PHOTOSYNTHESIS 14
UNIT 3: GENETICS 16
3.1: GENES 16
3.2: CHROMOSOMES 16
3.3: MEIOSIS 17
3.4: INHERITANCE 17
UNIT 4: ECOLOGY 19
4.1: SPECIES, COMMUNITIES AND ECOSYSTEMS 19
4.2: ENERGY FLOW 19
4.3: CARBON CYCLING 20
4.4: GREENHOUSE EFFECT 20
UNIT 5: EVOLUTION AND BIODIVERSITY 21
5.1: EVIDENCE FOR EVOLUTION 21
4.2: NATURAL SELECTION 22
5.3: CLASSIFICATION OF BIODIVERSITY 23
UNIT 6: HUMAN PHYSIOLOGY 26
6.1: STRUCTURE OF THE DIGESTIVE SYSTEM 26
6.2: THE BLOOD SYSTEM 28
6.3: DEFENSE AGAINST INFECTIOUS DISEASES 30
6.5: NEURONS AND SYNAPSES 32
6.6: HORMONES, HOMEOSTASIS AND REPRODUCTION 35
UNIT 7: NUCLEIC ACIDS 39
7.1 DNA STRUCTURE AND REPLICATION 39
7.1: TRANSCRIPTION AND GENE EXPRESSION 41
7.3: TRANSLATION 41
UNIT 8: METABOLISM, CELL RESPIRATION AND PHOTOSYNTHESIS 43
,8.1: METABOLISM 43
8.2: CELL RESPIRATION 44
8.3: PHOTOSYNTHESIS 47
UNIT 9: PLANT BIOLOGY 51
9.1: TRANSPORT IN THE XYLEM OF PLANTS 51
9.2: TRANSPORT IN THE PHLOEM OF PLANTS 54
9.3: GROWTH IN PLANTS 54
9.4: REPRODUCTION IN PLANTS 54
UNIT 10: GENETICS AND EVOLUTION 56
10.1: MEIOSIS 56
10.2: INHERITANCE 57
10.3: GENE POOLS AND SPECIATION 58
UNIT 11: ANIMAL PHYSIOLOGY 60
11.1: ANTIBODY PRODUCTION AND VACCINATION 60
11.2: MOVEMENT 62
11.3: THE KIDNEY AND OSMOREGULATION 64
11.4: SEXUAL REPRODUCTION 66
Notes:
2
,Unit 1: Cell Biology
1.1: Introduction to cells
1. Discuss possible exceptions to cell theory. 4 marks
▪ skeletal muscle fibers are larger/have many nuclei/are not typical cells
▪ fungal hyphae are (sometimes) not divided up into individual cells
▪ unicellular organisms can be considered acellular
▪ because they are larger than a typical cell/carry out all functions of life
▪ some tissues/organs contain large amounts of extracellular material
▪ e.g. vitreous humor of eye/ mineral deposits in bone/ xylem in trees/other
example
▪ statement of cell theory/all living things/most tissues are composed entirely of true
cells
2. Eukaryotic cells have intracellular and extracellular components. State the
functions of one named extracellular component. 4 marks
name of component: 1 max
▪ e.g. plant cell wall/cellulose/interstitial
▪ matrix/basement membrane/glycoprotein/bone matrix;
functions: 3 max
EITHER
▪ e.g. (plant cell wall) strengthens/supports the cell/plant (against gravity);
▪ prevents the entry of pathogens;
▪ maintains the shape of plant cells;
▪ allows turgor pressure/high pressure to develop inside the cell;
▪ prevents excessive entry of water to the cell;
OR
▪ helps cells to stick together/adhere;
▪ needed to hold cells/tissues together / example of cells/tissues holding together;
▪ forms interstitial matrix / forms basement membrane to support single layers of
cells;
▪ e.g. around a blood capillary;
▪ forms (part of the) filtration membrane in the glomerulus;
3. Explain how the surface are to volume ratio influences cell sizes. 3 marks
▪ small cells have larger ratio (than larger cells)/ratio decreases as size increases
▪ surface area/membrane must be large enough to absorb
nutrients/oxygen/substances needed
▪ surface area/membrane must be large enough to excrete/pass out waste products
▪ need for materials is determined by (cell) volume
▪ cell size is limited (by SA/Volume ratio)/cells divide when they reach a certain size
▪ reference to diffusion across/through membrane/surface area
4. Outline differentiation of cells in a multicellular organism. 4 marks
▪ differentiation is development in different/specific ways
▪ cells carry out specialized functions/become specialized
3
, ▪ example of a differentiated cell in a multicellular organism
▪ cells have all genes/could develop in any way
▪ some genes are switched on/expressed but not others
▪ position/hormones/cell-to-cell signals/chemicals determine how a cell develops
▪ a group of differentiated cells is a tissue
5. Describe the importance of stem cells in differentiation. 3 marks
▪ stem cells are undifferentiated cells;
▪ embryo cells are stem cells;
▪ stem cells can differentiate in many/all ways / are pluripotent/totipotent;
▪ differentiation involves expressing some genes but not others;
▪ stem cells can be used to repair/replace tissues/heal wounds;
1.2: Ultrastructure of Cells
6. Draw a labeled diagram to show
the ultrastructure of Escherichia
coli. 6 marks
Award 1 for each structure clearly drawn
and correctly labeled.
▪ cell wall – with some thickness;
▪ plasma membrane – shown as
single line or very thin;
▪ cytoplasm;
▪ pilus/pili – shown as single lines;
▪ flagellum/flagella – shown as
thicker and longer structures than
pili and embedded in cell wall;
▪ 70S ribosomes;
▪ nucleoid / naked DNA;
▪ approximate width 0.5 μm /
approximate length 2.0 μm;
Award 4 max if the bacterium drawn does
not have the shape of a bacillum (rounded-
corner rectangle with length approximately
twice its width). Award 4 max if any
eukaryotic structures included.
7. Draw a labelled diagram to show the organelles which are found in the
cytoplasm of plant cells. 6
marks
▪ rough endoplasmic
reticulum
▪ free ribosomes
▪ Golgi apparatus
▪ mitochondrion
▪ chloroplast
▪ vacuole
▪ nucleus
▪ lysosome
▪ smooth endoplasmic
reticulum
4
