2. What are Cells?
Cells are the basic structural and functional unit of life.
They are the smallest living material.
Robert Hooke first discovered cells in 1665 using a simple
microscope.
Organisms are made up of one or more cells.
One cell = unicellular
More than one cell = Multicellular
INTRODUCTION TO CELLS
3. Microscopes:
∗ Invented in the 1600’s.
∗ Not until the 1930’s that scientists began to
study cell structure in detail.
∗ 1839 – German scientist, Theodore Schwann,
developed the CELL THEORY.
Cell Theory - is an important biological concept which states
that:
All living things are made up of cells.
Organisms vary in size from unicellular to multicellular.
Every cell arises from pre-existing cells.
Cells are specialised to perform specialised tasks.
THE CELL THEORY
4. *Read page 20 of your textbook and then answer the
following questions:
1. Before the cell theory, what alternative theory
existed?
2.Who disproved this earlier theory?
THE CELL THEORY
5. ∗ Take in nutrients and carry out chemical reactions.
∗ Produce waste products.
∗ Make useful substances such as hair and bone.
∗ Reproduce by dividing in two.
∗ Some specialised cells can move. E.g.
muscle cells contract and sperm cells
can ‘swim’.
∗ Exchange gases with their surroundings.
www.3dscience.com/img/Products/3D_Models/Biol
WHAT DO CELLS DO?
6. THE SIZE OF CELLS
•Cells are measured using a unit of length called a micrometer (µm)
•1 µm = 1/1000 of a millimeter
•Organelles are measured using a unit called a nanometer (nm).
•1 µm = 1000 nm
•Bacteria = 1 µm
•Human Red Blood Cells = 10 µm
•Human Liver Cells = 50 µm
•Mesophyll cells (in plant leaves) = 100 µm
Cell Size & Scale Interactive
http://learn.genetics.utah.edu/content
/begin/cells/scale/
7. MICROSCOPES
There are two main types of Microscopes:
Light Microscope
•Can magnify up to 1500x.
•Light passes through thin tissue sections.
•Light is focused through a series of lenses – Eyepiece & Objective
Lens.
Electron Microscope
•Can magnify up to 100,000x.
•Beams of electrons pass through a vacuum and then through a thin
layer of tissue.
•Better detail resolution than light microscope (ability to see
separate objects that are close together).
8. THE LIGHT MICROSCOPE
Light Microscope Use - Refresher
http://www.youtube.com/watch?feature=player_detailpage&v=scEhgAiazzU
10. MICROSCOPES
•Magnification – The ratio of the size of
the image as viewed through the microscope
to the actual size of the object.
•Resolution – The ability to perceive fine detail
(measured as the smallest distance between two points
that allows the two points to be distinguished from on
another, rather than be seen as a single blurred image).
•Total Magnification = Magnification of the Eyepiece
Lens X Magnification of the Objective Lens
11. MICROSCOPES
Activities:
1.Complete the handout “Parts of the Microscope”
2.Complete the handout “Microscope Magnification”
3.Using the light microscopes, view a minimum of 3 slides. For each
slide draw a diagram that is:
• Fully labeled including specimen name, total magnification
and anything else of interest.
• Drawn in pencil
• Is appropriately sized.
4.Read page 29-34 of your textbook and then answer question 9-13
on page 34.
12. Clickview - ”The Cell – How It Works (22 minutes)”
CELL STRUCTURE &
FUNCTION
13. Cell Structure & Function
PROKARYOTES - Bacteria EUKARYOTES – Plants, Animals, Fungi,
Protists
Small Size (1 - 10µm) Large Size (10 – 100µm)
Circular DNA Linear DNA
No Nucleus Contains nucleus
Little internal organisation High level of internal organisation
No membrane bound organelles Contains membrane bound organelles
Single Chromosome Two or more chromosomes
Cell wall made of peptidoglycan Cell Wall (if present) made of
cellulose
•There are two basic forms of cells:
•Prokaryotic Cells – have a simple structure.
•Eukaryotic Cells – have a complex structure.
14. CELL STRUCTURE-
ORGANELLES
Organelles are tiny living structures inside the cell which are
responsible for cell metabolism – the chemical reactions that
take place within the cell.
Organelles that make up cells:
∗ Cytoplasm
∗ Nucleus
∗ Mitochondria
∗ Cell Wall
∗ Cell Membrane
∗ Ribosome
∗ Endoplasmic Reticulum (ER)
∗ Chloroplast
∗ Golgi Bodies
∗ Vacuole
∗ Lysosome
15. CELL STRUCTURE-
ORGANELLES
*Use the following slides to fill in the table below –
“Cell Structure and Function”
Name of
Structure
Appearance Function Diagram
e.g. Cytoplasm Jelly-like
substance that
occupies most
of the cell
Contains
dissolved
substances to
support the
organelles
16. CYTOPLASM
The cytoplasm is a jelly like substance which
occupies most of the cell in animals and a
narrow band in plants.
The watery fluid contains
dissolved substances and
tiny living structures called
organelles.
http://sciencecity.oupchina.com.hk/biology/
student/glossary/img/cytoplasm.jpg
17. NUCLEUS
Found only in eukaryotic cells.
The largest and most prominent feature of cells.
Spherical and usually located centrally in animal cells
and towards the edge of the cell wall in plants.
Double membrane boundary is called the nuclear
envelope. This contains nuclear pores. Around each
pore is a protein.
The nucleus controls the development and functioning of the cell.
It controls growth and reproduction (mitosis) and metabolism.
DNA is found in the nucleus. This is the hereditary information
that is passed on through generations.
18. ROLE OF DNA IN CELLS
DNA contains coded information for the synthesis of enzymes.
Enzymes are important molecules that are needed to speed up
chemical reactions.
A sequence of DNA that codes for a protein is called a gene. One
gene codes for one protein. Genes carry the information to
synthesise various molecules called gene products.
Even in the simplest cells there are hundreds of chemical
reactions that take place which means that hundreds of enzymes
are needed. Each of the enzymes needed is made up of different
genetic code. So, several hundred genes are needed to carry out
all necessary chemical reactions so the cell can survive and
reproduce.
Prokaryotic cells have several hundred genes. Eukaryotic cells
have several thousand genes.
19. MITOCHONDRIA
∗ Elongated, rod shaped organelle found in
the cytoplasm of all living cells.
∗ It is enclosed by a double membrane.
∗ The outer membrane forms a smooth
envelope enclosing the organelle.
∗ The inner membrane is extensively
folded inwards upon itself to produce a
vast number of finger-like projections.
∗ This is the site of aerobic respiration –
simple organic molecules (glucose) are
broken down to release energy.
∗ The mitochondria is referred to as ‘the
powerhouse of the cell’.
20. CELL WALL
Only found in plants.
The cell wall is a highly complex structure.
It is made up of a tough,
rigid and highly cross-linked
matrix of substances.
The cell wall gives shape
and strength to the cell.
http://library.thinkquest.org/06aug/01942/plcells/think
quest/cell-wall.gif
21. CELL MEMBRANE
The cell membrane is made up of two layers of fat molecules
(called a lipid bilayer).
Protein molecules are present between the lipid bilayer.
Different types of lipids and
proteins make up different
types of cells.
The lipid bilayer determines the
basic structure of the membrane.
The proteins allow substances to
enter and leave the cell.
http://library.thinkquest.org/C004535/media/cell_me
mbrane.gif
22. ENDOPLASMIC RETICULUM
This is a system of membranes that exists throughout the
cytoplasm.
It is important in the transport of materials from one part of
the cell to another.
Rough ER has ribosomes (small round organelles) attached to it.
It is the site of protein and membrane synthesis.
Some proteins made by rough ER may have carbohydrates
attached to them and are called glycoproteins. These are used as
cell membrane receptors.
Smooth ER does not have ribosomes attached. It is involved in
metabolic processes such as lipid synthesis and carbohydrate
metabolism. There are many enzymes embedded in smooth ER to
help carry out metabolic processes.
24. GOLGI BODY
These are stacks of flattened sacs made of smooth membrane.
They package and secrete proteins and carbohydrates made by
the cell.
Cells that are involved in secretion contain large amounts of golgi
bodies. E.g. salivary glands.
Golgi bodies also make carbohydrates for use outside the cell.
They are packaged in vesicles that
bud off from the golgi body,
migrate to and fuse with the cell
membrane to release the contents.
This secretion is known as
exocytosis.
25. VACUOLE
∗ The vacuole is a fluid filled space that is bounded by a membrane.
It is found as a relatively large structure in plants and as very
small structures in animal cells.
∗ The fluid contains solutes which include:
∗ Salts, in the form of ions
∗ Simple sugars
∗ Amino acids
•The main functions of the
vacuole are to maintain water
and salt balance and also the
shape of the cell.
•The vacuole can also store
wastes, contain pigment and
contribute to cell growth.
26. CHLOROPLAST
∗ Thylakoids store the pigment chlorophyll.
Chlorophyll captures energy for photosynthesis.
∗ Equation for photosynthesis:
Light
6CO2 + 6H2O C6H12O6 + 6O2
Chlorophyll
∗ The first stage of p/s occurs in the grana. The final stage, which
needs enzymes, occurs in the stroma. Glucose is produced.
•The chloroplast is a type of plastid (a small
particle involved in storage) and carries out the
process of photosynthesis.
•Chloroplast are bounded by two membranes.
Internally there are flattened sacs called
thylakoids. These are arranged in stacks called
grana. The fluid surrounding these sacs is
called stroma
27. LYSOSOME
Small, spherical, membrane-bound organelles that are
found in the cytoplasm of the cell.
They are formed by the golgi bodies.
Can contain enzymes which
breakdown macromolecules.
http://www.biology4kids.com/file
s/art/cell_lysosome1.gif
29. PLANT VS ANIMAL CELLS
Read page 25 & 26 of your textbook.
Class discussion – what are the key differences
between plant and animal cells?
Draw a fully labeled diagram of a plant cell and an
animal cell (pg. 25).
Answer questions 4-6 on page 29 of your textbook.
30. PLANT VS ANIMAL CELLS
Practical – Investigating Plant & Animal Cells
(See Handout)
32. QUIZ- CELLS & THEIR
ORGANELLS
Complete the quiz “Cells and their Organelles” and
hand up to be checked.
33. SURFACE AREA TO VOLUME
RATIO
The surface area of a cell refers to its exposed cell
membrane. The volume of a cell refers to the quantity
of protoplasm that must be supplied with its
requirements for metabolism.
For all cells, the membrane area must of sufficient
size for the entire cell contents or volume to be
supplied with its requirement for metabolism by
diffusion at the highest rate. This process will then
occur in the shortest possible time.
34. SURFACE AREA TO VOLUME
RATIO
1 cm Cube
SA : Vol
6 : 1
Surface Area is
six times the
Volume
3 cm Cube
SA : Vol
2 : 1
Surface Area is
twice times the
Volume
The membrane area is sufficient
size for diffusion to supply the
entire cell volume at a high rate.
The membrane area is insufficient
in size for diffusion to supply the
entire cell volume at a high rate.
Diffusion will take considerably
longer.
35. SURFACE AREA TO VOLUME
RATIO
•As cells increase in size, their surface area to volume ratio
decreases. As a cell gets bigger there is less surface area available
to supply the increasing volume.
•Increase in cell size could be detrimental to the cell as there may
not be enough surface area available to allow enough nutrients to
reach the interior of the cell. Therefore, surface area to volume
ratio has an effect on cell size.
•DNA can also have an effect on cell size.
If the volume is too large, it may not be
able to produce enough proteins and
enzymes to maintain a cell.
10 L
10 L
36. SURFACE AREA TO VOLUME
RATIO
• Read page 60-61 of your textbook and then
answer question 8 & 9 on page 62.
• Practical – ‘Surface Area to Volume Ratio’
37. MOVEMENT OF SUBSTANCES
IN AND OUT OF CELLS
The transport of molecules into and out of a cell can
be divided into two main categories:
1.Passive Transport
– no energy required
(Movement of molecules is with
the concentration gradient)
2.Active Transport
– energy required
(Movement of molecules is against
the concentration gradient)
38. MOVEMENT OF SUBSTANCES
IN AND OUT OF CELLS
Active & Passive Transport can be further divided
into:
Active Passive
Exocytosis Endocytosis Diffusion Osmosis
Pinocytosis Phagocytosis
Transport
Facilitated
Diffusion
39. DIFFUSION
Diffusion – the kinetic
movement of molecules or
ions from an area of high
concentration to an area
of low concentration.
* Does not require energy
40. OSMOSIS
Osmosis – the diffusion of water across a membrane.
Water will move from an area of low solute
concentration to high solute concentration.
.
41. SELECTIVE EXCHANGE
A membrane is not equally permeable to all substances.
Factors that can affect permeability include:
Size of particle – particles need to be smaller than
the pore.
Charge of particle – charged particles are more
difficult to go through.
Some proteins can act as channels, and others are
carrier proteins. This selects for particles that can
move across. We say the membrane is selectively
permeable.
42. SELECTIVE EXCHANGE
Facilitated Diffusion – Passive movement across a
membrane through a protein carrier.
“Cell Membrane Passive Transport – Cell Biology” http://youtube.com./watch?
v=JShwXBWGMyY
43. ACTIVE TRANSPORT
This is the opposite of Diffusion
Active Transport – substances move across the
membrane against a concentration gradient. A living
cell and ATP is needed.
Carrier proteins are always needed, therefore this
process is selective.
44. ACTIVE TRANSPORT & ATP
• ATP is used to transport the ion/molecule against
the concentration gradient.
• The phosphate attaches to the channel protein – it
becomes a phosphorylated protein.
• Another type of
molecule is then picked
up on the other side of
the membrane, and
once this has been
transported across
the protein becomes
dephosphorylated.
45. ENDOCYTOSIS
• This is the process where particles and large
molecules are taken into the cell. The membrane
encloses them in a vacuole. There are two types of
endocytosis:
• Phagocytosis
• Pinocytosis
46. PHAGOCYTOSIS
•This involves the intake of particles.
•The membrane folds near the particle, it encloses it in
a vacuole, it then breaks away from the membrane and
enters the cytoplasm.
•These vacuoles are called lysosomes and contain
digestive enzymes which breakdown the particle.
•Phagocytes are selective for particles.
•Certain cells in our immune system are phagocytic.
47. PINOCYTOSIS
•This is the intake of liquids and large molecules into
tiny vesicles that form at the surface of the cell.
•This process may be selective or non-selective.
48. EXOCYTOSIS
• This is the opposite of endocytosis.
• Secreted materials which are produced by the cell
are packaged into a vesicle which migrates to the
plasma membrane and
releases the contents.
• Manufactured material
comes from the ER and
packaging occurs by the
golgi body.
“Cell Membrane, Exocytosis & Endocytosis”
http://youtube.com./watch?v=K7yku3sa4Y8
49. MOVEMENT OF SUBSTANCES
IN AND OUT OF CELLS
Activities:
•Read page 62- 66 of the textbook and then answer questions 10-13
on page 67.
•Clickview – “Keeping It All Together – Cell Membrane” (31 minutes)
•Homework – Use your textbook/internet to draw a diagram for each
of the following:
• Diffusion
• Osmosis
• Facilitated Diffusion
• Endocytosis
• Exocytosis
•Review Material so far and add to your glossary.
50. CELLS ISSUES
INVESTIGATION
•Task Outline – see handout
•Part A
• 1 Lesson in Computer Room – Friday Week 4
• Due Mon Week 6
•Part B
• Three lessons in Computer Room
• Due Monday Week 8
•Part C
• Due Friday Week 8 (Supervised Assessment in Class)
51. ENZYMES
•Enzymes are proteins that can increase the rate at
which chemical reactions happen.
•Enzymes are usually proteins, and they act on one or
more compounds (called the substrate)
•Enzymes may:
∗ Break a single substrate down into two or more simpler
molecules (Catabolic Reactions)
∗ Cause two substrate molecules to form bonds and
become a single molecule
52. ENZYMES
How Do They Work?
Animation – How Enzymes Work
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html
53. ENZYMES
Lock & Key Hypothesis Vs Induced Fit Model….
• The substrate binds to the active
site on the enzymes using weak
bonds (often hydrogen).
• This causes a change in the shape
of the enzyme and the substrate –
The Induced Fit Model.
• It is NOT a lock and Key
relationship.
• However, each enzyme catalyses
only one type of reaction because
the active site on the enzyme and
its substrate are structurally
complimentary (‘fit’ together).
54. ENZYMES
Enzymes & Activation Energy….
• Enzymes increase reaction
rates by lowering activation
energy.
• The initial energy required to
start a reaction is known as
the activation energy in a
chemical reaction.
• These reactions initially
require energy, but then
release free energy once the
reaction is commenced –
Striking of a match
Activation Energy
http://www.youtube.com/watch?v=Dd1yi2aVoOc
55. ENZYMES
• Enzymes do not change the direction of a reaction
or the amount of product.
• Most chemical reactions are reversible and the
same enzyme can catalyse a reaction in either
direction:
∗ If there is more substrate present, the net reaction
will be to the right.
∗ If there is a net accumulation of product, the net
reaction will be to the left.
• Enzymes are not used up in the reaction, and they
remain unchanged at the end of the reaction.
58. ∗ All cells divide at some stage in their life cycle.
∗ When a cell divides one cell splits into two daughter
cells
Cell Division
59. ∗ When the cell divides to produce two
daughter cells each of the cells being
produced need their own DNA.
∗ Thus before cell division the amount of
DNA in the cell needs to double.
∗ This process is referred to DNA
replication
Cell Division
60. ∗ Bacteria divide by a process known as binary fission.
∗ This means that each bacterial cell essentially divides in
2.
∗ Most bacteria have a single chromosome of DNA.
∗ Prior to cell division this chromosome replicates
itself and the two chromatids remain coiled
together in the cytoplasm
∗ Each daughter cell produced is genetically identical to
the
to the parent cell.
Cell Division – Binary Fission
61. ∗ This method of reproduction can occur within 20
minutes or so.
∗ This can result in exponential growth of bacterial
population
Cell Division – Binary Fission
62. ∗ Mitosis is the term that describes the division process that
eukaryotic cells undergo
∗ An easy way to remember mitosis is that it produces two cells
at the end. (MI- TWO- SIS)
∗ Cells undergo a cell cycle in which there are times of growth,
then preparation for division including the duplication of
chromosomes.
∗ There are 4 phases of Mitosis
* Prophase
* Metaphase
* Anaphase
*Telophase
Mitosis
63. ∗ This resting phase where the cell is
growing is called interphase.
∗ During interphase the DNA is present in
the nucleus in the form of chromatin,
which is basically stretched out
chromosomes.
∗ At the end of interphase the DNA in the
nucleus replicates itself.
∗ At the conclusion of interphase the cell
starts mitosis.
Interphase
64. ∗ Changes in the nucleus and cytoplasm occur during prophase.
∗ In the nucleus the chromatid fibres coil tightly and become visible
under the microscope.
∗ Each chromosome has duplicated and consists of two Identical
sister chromatids joined at the centromere.
∗ In the cytoplasm microtubules appear as spindle fibres and
centrioles move toward the poles of the cell. These are both a part
of the cytoskeleton.
Mitosis - Prophase
65. ∗ In the cytoplasm, microtubules or spindle fibres radiate from
the poles toward the cells equator and the chromosomes
become aligned at the metaphase plate which is an imaginary
line halfway along the cell.
∗ The microtubules become attached to the centromeres and
the centrioles (in animals).
∗ This whole structure is called a spindle.
Mitosis - Metaphase
66. ∗ Anaphase begins with the pairs of centromeres of the
chromosomes divide and the sister chromatids are pulled
apart.
∗ Each chromatid is now considered to be a daughter
chromosome.
∗ These chromosomes are drawn toward the
opposite poles of the cell by microtubules
attached to the centromeres.
Mitosis - Anaphase
67. ∗ As the daughter chromosomes are drawn
to the opposite poles, daughter nuclei
begin to form and the nucleoli reappear.
∗ The chromosomes uncoil to form chromatin
and the cytoplasm forms a cleavage furrow.
∗ The cell pinches in along this furrow and the
microtubules involved act like a ligature
pinching it off.
Mitosis - Telophase
68. ∗ http://www.youtube.com/watch?v=HYKesI9jL8c
∗ It is very important that cells which divide by mitosis
or binary fission have the same chromosomes as the
parent if they are to function normally.
∗ This is ensured by DNA replication producing two
copies of all the DNA in the cell. Secondly mitosis acts
to make sure that sister chromatids separate evenly
and become identical chromosomes.
Mitosis
69. ∗ Cells won't divide all the time.
∗ Cells need to control when they are going to divide.
∗ Factors which control cell division can be external, ie outside
the cell or inside the cell.
∗ If certain nutrients aren't present outside the cell then it will
not divide. This is called nutrient dependence.
∗ Research has shown that some cells will only divide when they
are attached to something. This is called anchorage
dependence.
Regulation of Cell Division
70. ∗ Some factors regulate the cell cycle that aren't chemical in
nature. Contact inhibition is an example of this.
∗ If a cell is surrounded by other cells it will not generally
divide.
∗ This is called contact inhibition or
density dependence.
∗ If cells are removed from around
it then cells at the edge will divide
until the gap is closed
Regulation of Cell Division
71. ∗Carcinogens are chemicals that cause
cancer.
∗Cancer is uncontrolled cell division.
∗Cancer is caused by mutations in the DNA
of cells. These mutations cause changes in
the structure and function of some of the
chemicals that regulate cell division
Cancer
72. ∗ Cancer begins with one abnormal cell. This cell divides through
mitosis and forms a small growth.
∗ This growth can then metastasise or break apart and the
abnormal cells will keep growing in other parts of the body,
forming secondary tumours.
∗ http://www.youtube.com/watch?v=rrMq8uA_6iA
Cancer
74. ∗ Cancer can be treated by radiotherapy, in which a
concentrated dose of radiation is targeted at the cell which
will damage the DNA in the cell further, stopping the cells
from growing, and chemotherapy, which does a similar thing
but with chemicals to kill off the infected cells.
Clickview – Catching Cancer (50 mins)
Treatment
