Class Presentation on Topic 2
4A– IB Biology HL
Key:
Angel Alabe/Abbey Currence
Larger
subunit
Small
subunit
rER – rough endoplasmic reticulum
RIBOSOMES
Translation & Channeling of Proteins (contd.)
RIBOSOMES
Translation & Channeling of Proteins (contd.)
Structure
 A membranous system of
interconnected tubules and
flattened sacs called
cisternae.
 Rough Endoplasmic
Reticulum – studded on its
outer surface with
ribosomes.
Function
 It transports materials
throughout the internal
region to cell.
 Membrane factory for cells;
it grows in place by adding
membrane proteins and
phospholipids to its
membrane
 It is involved in protein
development and transport.
Content
 Most secretory proteins in
the organelle are
glycoprotein (proteins that
have carbohydrates
covalently bonded to them).
The carbohydrates are then
attached to the proteins the
rough endoplasmic
reticulum by specialized
molecules built into its
membrane.
Capillary
I
Storage vesicles
II
III
 Definition: The organelle that “functions as a selective
barrier or boundary for every cell, and regulates the
sufficient passage of oxygen, nutrients, and wastes to
service the entire cell.”
 Also known as:
 Membrane
 Plasma membrane
 Cell surface membrane
 Organelles have membranes, too, that are similar in
structure
Micrograph image of
part of a cell:
I = Membrane (of the
nuclear envelope)
II = Mitochondrion
 Structure Overview: There is a bilayer (double layer) in
which lipids (fats) stay on the outer part, and proteins pass
through the middle among the lipid tails
 Phospholipids: Made up of glycerol (3 carbon compound)
 2 of glycerol carbons are attached to fatty acids
 3rd glycerol carbon attached to highly polar organic alcohol
(related to phosphate)
 Has a hydrophilic (polar, water
soluble) head
 Has two hydrophobic (nonpolar,
water insoluble) tails
 The tails have a weak bond, causing
the cell membrane to be very flexible
 The heads are connected by
hydrogen bonds, and they maintain
the structure of the membrane
Cholesterol:
 Found in animal cells ONLY
 Located in the tails of phospholipids
 Determines the membrane fluidity
 Membranes MUST be fluid in order to function
properly
 Consistency is similar to olive oil
 Temperature change affects fluidity
 Instead of cholesterol, plant cells use unsaturated and
saturated fatty acids
 Many different varieties – Also known as amino acids
 Two most prominent types are:
 Integral proteins
 Peripheral proteins
Integral:
 Hydrophilic regions – polar
amino acids (outer
regions)
 Hydrophobic regions –
nonpolar amino acids
(central regions)
 Regulate the entrance and
exit of molecules through
the cell membrane
I
I = Integral Protein
Peripheral:
 Stays on the surface
of cell membrane
 Attached to integral
proteins
 Also attach to
glycoproteins (another
type )
I = Glycoprotein
II = Integral protein
III = Hydrophilic
phosphate head
6 basic functions of proteins:
1) Enzymatic action: relates to metabolic reactions
2) Cell adhesion: when proteins connect (junctions)
3) Cell-to-cell communication: for identification
4) Hormone binding sites
5) Passive transport channels
6) Active transport pumps
Two types of transport are:
Passive transport: movement due to
redistribution for different concentrations,
no energy expended
Diffusion
Osmosis
Active transport: movement against
concentration gradient, energy is expended
(in the form of ATP)
Diffusion: movement of non-water particles
from a concentration that is high to one that
is low
Movement between protein channels
(phospholipid molecules)
Facilitated diffusion: carrier proteins
combine with substances to help with
movement – protein shape changes but no
energy is required still
 Exam Question Example: Channel Proteins
 The diagram below shows a channel protein in a
membrane. Which parts of the surface of the
protein would be composed of polar amino acids?
 A. I and II only
 B. II and III only
 C. III and IV only
 D. I and IV only
(Answer is A)
Osmosis:
Happens along the concentration gradient
Involves ONLY water molecules
Happens with partially permeable membranes
Movement caused by concentration difference
inside and outside the cell membrane
Goal of passive transport is to reach
equilibrium on both sides
Osmosis:
Hyperosmotic – higher concentration
Hypo-osmotic – lower concentration
Water moves from
hypo-osmotic → hyperosmotic
Iso-osmotic – equilibrium, no movement
Osmosis: influencing factors of substances that
are being transported are…
Size – small = easy movement
large = difficult movement
Charge – nonpolar = easy movement
polar = difficult movement
(Partially
permeable)
Uses aquaporins (proteins with specialized water channels)
Trying to achieve equilibrium (iso-osmotic)
Does require energy in the form of ATP
Moves against a concentration gradient that
needs energy
Process helps cell maintain equal
concentrations inside and outside the
membrane
Sodium-potassium pump: (way for moving these ions)
1.
Specific protein in cell membrane binds to three sodium ions
from inside the cell
2.
Binding of sodium ions causes phosphorylation (the activation
of the protein enzymes through the addition of PO4-3 from the
phosphate molecule from the AT
3.
Phosphorylation causes protein to change shape and expel
sodium ions that were inside the protein to outside the cell
4.
2 potassium ions enter the protein from outside the cell which
causes the phosphate to be released
5.
When the phosphate is released, protein restores to its original
shape and the potassium ions are released into cell
Endocytosis: process that allows
macromolecules to enter the cell
Exocytosis: process that allows
macromolecules to leave the cell
In endocytosis, portion of membrane is
pinched to surround a particle, and a vesicle
forms leading to the cytoplasm
Vesicle allows protein to eventually reach
nucleus
Cell Organelles - Cell Wall
Class Presentation on Topic 2
4A– IB Biology HL
By: Robert Jennings
Cell Wall
 The cell wall is
a semi-rigid
structure
composed
mainly of
cellulose, and
its purpose is
to give the cell
structure and
protection.
Structure/Composistion-Cell Wall
 Consist of three layers.
 Middle lamella
1.
Formed during cell division
2.
Makes up outer wall of cell
3.
Composed of proteins and pectic compounds.
 Primary wall
1.
Formed after middle lamella.
2.
Consist of rigid skeleton made of cellulose microfibrils embedded in a gel-like
matrix composed of pectic compounds, hemicellulose, and glycoproteins.

Secondary wall
1.
After cell enlargement is completed
2.
Very rigid and provides incredible strength.
3.
Layered and made of cellulose, lignin, and hemicellulose.
Function-Cell Wall
 Determines the shape of the particular cell.
 Provides strength to the cell but is still somewhat flexible.
 Controls the turgor pressure in a cell. Turgor is the pressure
applied to the cell from the constituents inside it.
 Since the cell wall is permeable it allows for proteins and
other small molecules to come in and out of the cell.
 Protects cells from pathogens and microorganisms.
 Reserves carbohydrates that can be used in times of need.
Vesicles-Cell Wall
 Vesicles are smooth pieces of endoplasmic reticulum or ER that break
off and transport things such as proteins throughout the cell.
 Vesicles are storage organelles.
 Vesicles, carry molecules that are too large to pass directly through the
membrane to destinations outside of the cell.
 Vesicles form when coat proteins wrap themselves around large
molecules. This spherical product then buds out of the ER (endoplasmic
reticulum) and is carried like cargo out of the cell’s membrane.
Miscellaneous-Cell Wall
Prokaryotic
cells have a
cell wall as
well as plant
cells.
•Composed of:
•Membrane
•Proteins and Enzymes
If the lysosome stops or
explodes, the cell will break
down
 Scientifically, lysosomes are organelles that contain
digestive enzymes. So, in other words, the lysosomes
are essentially the stomach of the cell.
 Intracellular digestive centers that derive from the
Golgi apparatus
 The enzymes that lysosomes have can breaks down
the substances within the cell
The lysosome performs it’s job
by helping digest the microbe
 Collects, packages, modifies, and distributes
materials synthesized in the cell
 Is the post office of the cell
 Tells products where to go in or out of the cell.
 Main body is cisternae. Which are flat and stacked on
top of each other. Products travel through cisternae.
 Two sides. Cis side is close to the rough ER. Trans
side.
 Vesicles go in one side and come out the other.
 Modifies Vesicles by adding enzymes or removing
sugar and adding it own.
Class Presentation on Topic 2
4A– IB Biology HL
Nucleus: Function
*The main
function of the
nucleus is to
regulate activity
within a cell.
*Ex. Aids in
reproduction
Nucleus: Structure
* Bordered by a
double
membrane,
nuclear envelope.
* Contains a
nucleolus
Nucleus: Contents
* Contains
most of
the cell’s
DNA *
Nucleus:
Prokaryotic vs. Eukaryotic:
*Prokaryotic
cells do NOT
have a
nucleus.
* Eukaryotic
cells DO have
a nucleus.
Nucleus:
Nuclear Membrane
*Double layered
structure that separates
nucleus from cytoplasm
* Itcontains pores that
allow communication
with cytoplasm
Nucleus: Locations
* A nucleus is
located in the
center of a cell.
Nucleus: Micrograph
* A Micrograph is
a photo taken by
a microscope!
Nucleus: DNA and RNA
* DNA carries the genetics of
a cell and consists of
thousands of genes
* The RNA is processed so
that non-coding parts are
removed. After this, the RNA
is removed from the nucleus.
Nucleus:
Haploid nucleus + Diploid nuclei
In cell division:
*Haploid nuclei contain only
half of the number of
chromosomes (23
chromosomes)
* Diploid nuclei contain both
pairs of chromosomes (which is
46 chromosomes)
By
Sarah Liles, Natashia Gavarrete, and Matthew Juve
Period 4A
IB Biology Year 1 HL
 Structure Within (Contents):
 Rod-shaped organelles that appear throughout the cytoplasm.
 Have their own DNA.
 Circular chromosome similar to that in bacteria cells, allowing for
autonomy within the cell.
 Has a smooth outer membrane. The inner membrane is a semifluid substance called a matrix, and lies between the two
membranes.
 Cristae provides a huge internal surface area for the chemical
reactions of the mitochondria to occur.
 Structure:
 an outer membrane that encloses
the entire structure
 an inner membrane that encloses a
fluid-filled matrix
 between the two is the
intermembrane space
 the inner membrane is elaborately
folded with shelflike cristae projecting
into the matrix.
 a small number (some 5–10) circular
molecules of DNA
 Uses in prokaryotic cells:
Prokaryotic
Cell
 They are not present in
prokaryotic cells.
 Uses in eukaryotic cells:
 the energy producing
structures of Eukaryotic cells
and supply the cells with ATP.
 Structures which produce the
cell’s energy.
 Powerhouses of the cell.
Eukaryotic
Cell
 Functions:
 Main function: production of
energy in the form of adenosine
triphosphate (ATP)
 Performs the process of
programmed cell death. It occurs
during development as the
organism is pruning away
unwanted, excess cells.
 involved in building, breaking
down, and recycling products
needed for proper cell
functioning.
 Mitochondria’s role in cellular respiration:
 known as the powerhouses of the cell.
 They are organelles that act as a digestive system that takes
in nutrients and breaks them down.
 This process creates energy for the cell.
 By producing this nutrients and power it contributes to
creating cell energy other wise known as cellular
respiration.
 The Mitochondrion's perfect shape allows for a good place for
cellular respiration to occur, and maximize the effort given.
 Acetyl-CoA: produced in mitochondria through the oxidation of
fats.
 Pyruvate is converted to Acetyl Coenzyme (CoA) via active transport
when entering the mitochondria.
 The entry compound for the citric acid cycle in cellular respiration,
formed from a fragment of pyruvate attached to coenzyme while
transporting through the organelle.
 Carries out key reactions in the cells of eukaryotes.
 ATP Synthetase occurs in these organelles.
 It is the location of Chemiosmosis.
 The diffusion of ions across a selectively-permeable membrane.
More specifically, it relates to the generation of ATP by the
movement of hydrogen ions across a membrane during cellular
respiration
 Electron Micrograph
 Mitochondrion appear as bacteria sized ellipses.
 Vary in size and width, but this is hard to see on a two
dimensional electron micrograph.
 Krebs cycle- Cycle that
accounts for the
oxidation of
carbohydrates in
prokaryotes and
eukaryotes.
 Mitochondria produce
the ATP in the Krebs
cycle in eukaryotes.
 There are no
mitochondria in bacteria.
 Mitochondria vs. chloroplasts
 Both are circular in shape.
 Both are involved in ATP
production.
 Chloroplasts are slightly larger.
 Mitochondrion generate ATP with
glucose during cell respiration.
 Chloroplasts generate ATP through
sunlight.
Exam Question
Example #1
The electron micrograph below shows part of several
pancreatic islet cells.
(a) Identify the structures labelled I, II and III in the
micrograph above and give a role for each one. (3)
(b) (i) Using the letter A, identify one location on the
micrograph where transcription takes place. (1)
(ii) Using the letter B, identify one location on the
micrograph where chemiosmosis occurs. (1)
Exam Question
Example #1
Markscheme
Capillary
Mitochondria
Structure
Role
mitochondria
produce ATP / site of
(aerobic) respiration;
nucleus
contains genetic
information /
produces RNA /
site of replication;
(rough)
endoplasmic
reticulum
(site of) translation /
protein production /
protein
transport;
Storage vesicles
Nucleus
*Transcription takes place
** Chemiosmosis
(Rough) Endoplasmic Reticulum
Exam Question
Example #2
The electron micrographs below show mitochondria in
longitudinal section. The mitochondrion in A is from a
bat pancreas cell and that in B is from a mouse liver
cell. (Next Slide)
(a) Annotate the micrographs to show two similarities
in the structure of the mitochondria. (2)
(b) The mitochondria differ in size. State two other
differences that are visible in the mitochondria. (2)
(c) Predict, with two reasons, which of the
mitochondria would have been able to produce ATP at a
greater rate.
Exam Question
Example #2
Markscheme
BAT
Similarities
MOUSE
Cristae
Matrix/Ribosomes
.
Differences:
Shape
Arrangement of cristae
Density of cristae
Amount of matrix
granules/any reference to
dark dots *ribosomes not
accepted
Which mitochondria would have been able to
produce ATP at a greater rate & why:
Bat’s
Larger size/volume
Greater surface area of cristae/more cristae
Closeness of mitochondria in mouse reduces rate
Exam Question
Example #7
(a) Distinguish between the terms resolution and
magnification when applied to electron microscopy.
(2)
The electron micrograph below shows part of a cell.
(Next Slide)
(b) Identify the structures labelled I and II. (2)
(c) State one function of the structure labelled II. (1)
(d) Deduce, with a reason, whether this cell is eukaryotic
or prokaryotic. (1)
(Total 6 marks)
Exam Question
Example #7
Markscheme
resolution: separate points / focus
clearly / greater detail / clarity;
magnification: size of image / view
/ picture
Function of mitochondrion (II):
aerobic respiration;
correct specific reaction / pathway
occurring in mitochondria /
ATP production; Do not accept
“energy production” alone.
I: membrane / (nuclear) envelope
II: mitochondrion / mitochondria
Eukaryotic:
internal membranes / membrane
bound organelles /
presence of mitochondria / double
nuclear membrane;
•Approximately the same size as a
bacterial cell
•The parts
-Thylakoid: flat shaped membrane
sacs that absorbed light for
photosynthesis.
-Stroma: Contain the chloroplast
DNA and ribosomes as well as many
enzymes that aid in photosynthesis
-Double membrane: two membranes
that separate the contents from the
cytosol. Also create a small space
between the membranes.
•Contains enzymes in the Stroma which helps
complete photosynthesis.
- RuBP carboxylase enzyme- catalyzes the first step
of the Calvin Cycle.
•Main function is photosynthesis
•The Calvin Cycle- In the Calvin Cycle, the enzymes
of the chloroplast are in the stroma.
•Tylakoids of chloroplasts get positive protons using
energy obtained from light sources, thus the small
volume size is advantageous to concentrate protons
more rapidly.
•Plastids
•Have three distinct parts: the intermembrane space,
the stroma, and the thylakoid space.
Chloroplasts
Contain
stroma
Used for
photosynthesis
Only in plant
cells
Both
-Same size
-Double
membrane
s
- 70S
ribosomes
Mitochondria
Contain
matrixes
ATP energy
Cellular
respiration
•Chlorophyll:
•Green pigment
•Plants are green due to
the green pigment of
chlorophyll (used in
photosynthesis).
•Absorbs violet-blue
and red colors and
reflects green light
(visible light)
•Chemical structure of
chlorophyll
Works Cited
 http://learn.genetics.utah.edu/content/begin/cells/
vesicles/
 http://biology.clc.uc.edu/courses/bio104/cells.htm
 AP Edition Biology Textbook.
 Biology HL Textbook.