IB Biology Study Guide
1.2 Ultrastructure of cells
Name: _________________________________
Understandings:
 Prokaryotes have a simple cell structure without compartmentalization.
 Eukaryotes have a compartmentalized cell structure.
 Electron microscopes have a much higher resolution than light microscopes.
Applications & Skills:
1. List and describe the structures and functions of organelles within:
a. exocrine gland cells of the pancreas
b. palisade mesophyll cells of a plant leaf
2. Explain the process of binary fission in prokaryotes.
3. Draw the ultrastructure of prokaryotic cells based on electron mircographs.*
4. Draw the ultrastructure of eukaryotic cells based on electron micrographs.**
5. Identify organelles and deduce the function of specialized cells from interpretations of electron micrographs.
Guidance:
 *Drawings of prokaryotic cells should show the cell wall, pili, and flagella, and plasma membrane enclosing
cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA
 **Drawings of eukaryotic cells should show a plasma membrane enclosing cytoplasm that contains 80S
ribosomes and a nucleus, mitochondria, and other membrane bound organelles are present in the cytoplasm.
Some eukaryotic cells have a cell wall.
Theory of Knowledge:
 The world that we inhabit is limited by that world the world that we see. Is there any distinction to be drawn
between knowledge claims dependent upon observations made by sense perception and knowledge claims
dependent upon observations assisted by technology?
Understandings
1. Prokaryotes have a simple cell structure without compartmentalization.
2. Drawings of prokaryotic cells should show the cell wall, pili and flagella, and plasma membrane enclosing
cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA.
http://www.tokresource.org/tok_classes/biobiobio/biomenu/prokaryotic_cells/prokaryote_500.jpg
Prokaryotic Cells
cell wall:
flagella:

always present


composed of peptidoglycan

provides physical protection

base is embedded in the cell wall

maintains cell shape

using energy, they can be rotated, to propel the

prevents bursting in hypotonic environment
corkscrew shape
cell from on area to another

plasma membrane:

unlike eukaryotic flagella, they are solid and
inflexible, working like a propeller
thin layer mainly composed of phospholipids
pushed up against the inside of the cell wall

structures protruding from the cell wall with a
provides selectively permeable barrier between
cytoplasm:

homeostatically controlled interior and
fluid filling the space inside the plasma
membrane
fluctuating exterior environments

water with many dissolved substances

controls entry and exit of substances

contains many enzymes

can also pump substances in or out by active

contains ribosomes
transport

does not contain any membrane-bound

can produce ATP by cell respiration
organelles

pili:
metabolism

protein filaments protruding from the cell wall

can be pulled in or push out by a ratchet
mechanism

used for cell to cell adhesion

used when bacteria stick together to form
nucleoid:

used when two cells are exchanging DNA during


small granular structures (70S)

smaller than eukaryotic ribosomes which are
80S

sites of protein synthesis
total amount of DNA is much smaller than in
eukaryotes


DNA is circular and naked (not associated with
protein)
conjugation
ribosomes:
region cytoplasm containing the genetic
material (usually one molecule of DNA)
aggregations of cells

carries out the chemical reactions of
the nucleoid is stained less densely than the
rest of the cytoplasm because there are fewer
ribosomes in it and less protein
3. Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
http://ib-biology2010-12.wikispaces.com/file/view/bacterial_cell.gif/179867541/bacterial_cell.gif
4. Application: Prokaryotes divide by binary fission.
http://gleesonbiology.pbworks.com/f/1159266492/binary%20fission.JPG
5. Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
Guidance: Drawings of eukaryotic cells should show a plasma membrane enclosing cytoplasm that contains 80S
ribosomes and a nucleus, mitochondria and other membrane-bound organelles are present in the cytoplasm.
Some eukaryotic cells have a cell wall.
Eukaryotic Cells
Free ribosomes:
 sites of protein synthesis for use within the
cytoplasm
 ribosomes are constructed in the nuclear region
called the nucleolus
Rough endoplasmic reticulum:
 flattened membrane sacs (cisternae)
 ribosomes attached to outside of cisternae
 proteins synthesized by ribosomes enter
cisternae
 proteins collected within cisternae are
packaged in vesicles
 vesicles transport proteins to Golgi apparatus
Lysosomes:
 spherical vesicles formed by Golgi apparatus
 contain hydrolytic/digestive enzymes
 enzymes for breaking down ingested food,
damaged organelles, or entire cells
Golgi apparatus:
 consists of flattened membrane sacs called
cisternae
 unlike ER, cisternae are curved, shorter, and
lack ribosomes
 proteins received from arriving vesicles are
processed
 carbohydrates added to proteins to form
glycoproteins
 vesicles of glycoproteins exit Golgi for
exocytosis or intracellular use
Nucleus:
 double membrane bound, containing pores for
transport of proteins and ribosomes
 contains chromosomes, made of DNA + protein
 uncoiled chromosomes = chromatin
 site of DNA replication and transcription into
RNA
Mitochondria:
 double membrane bound
 inner membrane invaginated to form cristae
 site of aerobic respiration, producing ATP
Compare prokaryotic & eukaryotic cells.
Prokaryotic
 naked DNA
 DNA in cytoplasm (no nuclear membrane)
 No membrane-bound organelles (no
mitochondria, ER, golgi)
 ribosome size = 70S
 Only bacteria
 Size: 1 - 10 µm
 Evolved at least 3.5 billion years ago
Eukaryotic
 DNA associated with proteins
 True nucleus (enclosed by nuclear membrane)
 Many membrane-bound organelles
(mitochondria, ER, golgi) to compartmentalize
functions
 ribosome size = 80S
 All cells other than bacteria
 Size: 2 - 1000 µm
 Evolved 1.5 - 2 billion years ago
7. Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized
cells. Electron microscopes have a much higher resolution than light microscopes.
1.
2.
3.
4.
5.
nucleus
mitochondria
plasma membrane
nucleoli
red blood cells (in adjacent blood vessel)
8. Compare prokaryotic and eukaryotic cells.
Prokaryotic
 naked DNA
 DNA in cytoplasm (no nuclear membrane)
 No membrane-bound organelles (no mitochondria, ER, golgi)
 ribosome size = 70S
 Only bacteria
 Size: 1 - 10 µm
 Evolved at least 3.5 billion years ago
Eukaryotic
 DNA associated with proteins
 True nucleus (enclosed by nuclear membrane)
 Many membrane-bound organelles (mitochondria, ER, golgi) to compartmentalize functions
 ribosome size = 80S
 All cells other than bacteria
 Size: 2 - 1000 µm
 Evolved 1.5 - 2 billion years ago
9. Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade
mesophyll cells of the leaf.
Animal cells
 no cell walls
 no chloroplasts
 lacking or small vacuoles
exocrine gland cells of the pancreas
http://ak47boyz90.files.wordpress.com/2010/09/8.png
Plant cells
 cellulose cell walls
 chloroplasts
 large central vacuole
palisade mesophyll cells of the leaf