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Cells 1.1

Bio - Cells 1.1
Cell Theory
1. All living things are composed of cells / cell products
2. Cell is the smallest unit of life
3. Ce;s only arise from preexisting cells
But the current cell theory added two more..
4. Cell contain a blueprint for their growth, development and behaviour
5. Cells are the site of all of the chems reactions of life
● Cellular respiration & photosynthesis ( an exp. of chem reaction )
Explanations of Each Theory
1. Living organism are composed of cells
● The internal structure of LO is very intricate & built up from very small individual
● Unicellular and multicellular organism
● Vary in size and shape
○ Bacterial cells
○ Red blood cell
○ Nerve cell
○ Skeletal muscles
But cells share certain common feature :
● Every living cell is surrounded by a membrane ( not share by viruses )
● Cells contain genetic material
● Chemical reactions are catalyzed by enzymes
● Cells have their own energy release system
2. The cell is the smallest unit of life
● Specialised structures within cells ( organelles ) carry out different functions.
Organelles cannot survive alone
Paramecium shows the 2 contractile vacuole, the oral groove with the formation of a
new food vacuole
3. Cell only arise from preexisting cells
● Cell multiply through division
● All life evolved from simpler ancestor
● Mitosis results in genetically identical diploid daughter cells
● Meiosis generate haploid meters ( sex cells )
Exceptions to the cell theory
● Trends ( things that appear to be found generally rather than just a specific case
○ a trend of animals - generally they have legs.. some have 2 some have 4 (
exceptions )
● Theory ( a way of interpreting the natural world allowing us to make predictions )
● Discrepancies ( sometimes exceptions are found from a general trend )
● e.g Robert hooke looked at many different cells and discovered a general trend.
That is, tissue consist of cells
Micrope is an optical instrument that uses lens to enlarge / magnify objects that can’t be
seen by the naked eye
There are 2 types
● Light microscopes ( use light beams and lenses )
● Electron microscope ( beams of electrons and magnets)
○ SEM ( electron beams r reflected off the specimen )
○ TEM ( electron beam passes through specimen )
Parts of the microscope
- Review in the ppt
1mm = 1000 micrometer
Scale bar
A line added to a micrograph / drawing to help show the actual size of the structures
It's important in calculations
Use these calculation to find the magnification / actual size of images
1. Convert all units to make them the same ( where appropriate )
2. Perform calculations
3. Convert answers to appropriate SI units, using scientific notation where needed
4. Always convert to mm then to micrometer
Magnification : measured length/ scale bar label
Actual size : measured length / magnification
Calculating magnification
Most electron micrographs have a Scale bar that will allow u to calculate the
magnification of the photograph
Using the scale bar :
1. Measure the scale bar on the photograph in mm
2. Convert these mm into the same units as the scale bar
3. Divide this no. by the no. of the scale bar
Magnification : put x in the end
Magnification : 350x
Image : 250mm
Actual length
0.71mm or 710 micrometer
* Isn't that a bit big for a cell? More on size of cells later
Sperm cell tail 50 micrometer
Draw 75 mm long
Magnification : ?
- 75 / 50
- 1.5 x 1000
- 1500 x
1.1 A 1 Questioning the cell theory using atypical exam. Including striated
muscle, giant algae and aspirate fungal hyphae
1. Striated muscle
● Challenges the idea that a cell has one nucleus
● Muscle cell have more than one nucleus per cell - why a lot - to generate faster
and produce more energy )
● Muscle cells called fibres can be very long ( 300mm)
● They are surrounded by a single plasma membrane but they are multinucleated
● This does not conform to the standard view of a small single nuclei within a cell
2. Aseptate fungal hyphae
● Challenges the idea that a cell is a single unit ( no separation between them, this
comprises one cell )
● Fungal hyphae are again very large with many nuclei and a continuous
● The tubular system of hyphae form dense networks called mycelium
● They have cell walls composed of chitin
● The cytoplasm is continuous along the hyphae with no end cell wall or membrane
3. Giant Algae ( Acetabularia )
● Acetabularia is a single celled organism that challenged both the idea that cell
must be simple in structure and small in size
● Gigantic in size ( 5-100mm)
● Couples in from, it consist of three anatomical parts
○ Bottom rhizoid ( that resembles a set of short roots )
○ Long stalk
○ Top umbrella of branches that may fuse into a cap
● The single nucleus is located in the rhizoid
1.1 U2 Organism consisting of only cell carry out all function of life in that cell
Characteristics of living organism
● Movement - all living things move
● Reproduction - living things produce offsprings, either sexually or asexually
● Sensitivity - response - living things can respond to and interact with the
● Homeostasis - the maintenance and regulation of internal cell conditions, e.g
water and pH
● Growth - living things can grow or change size/ shape
● Respiration - metabolism - the well of all enzymes -catalysed reactions in a cell
or organism, e.g respiration
● Excretion - the removal of metabolic waste
● Nutrition - feeding by either the synthesis of organic molecules ( e.g
photosynthesis ) or the absorption of organic matter
○ Autotroph and heterotroph
How to memorize the characteristics of living : MR H GREN
Examples :
Paramecium shows the functions of life
Nutrition - food vacuoles contain organisms the paramecium has consumed
- Heterotrophic ( it eats smaller organism, gets food from outside )
- Most metabolic pathways happen in the cytoplasm
- The plasma membrane control the entry and exit of substance including explosion of
metabolic waste
- Exocytosis
- Contractile vacuole fill up with water and expel it thro the plasma membrane to
manage the water content
- The wave action of the cilia moves the paramecium in response to changes in the
environment e.g towards food
- The nucleus can divide to support cell division by mitosis, reproduction is often
- After consuming and assimilating biomass from food the paramecium will get larger
until it divides
Chlorella - undergo the same as paramecium
Some differences are…
- Nutrition : photosynthesis happens inside the chloroplast to provide the algae with food
- Reproduction - mitosis
- Excretion - plasma membrane control the entry an exit of the subs including the
diffusion out of waste oxygen
- It's not a true plant , the cell wall is not made out of cellulose
- Photosynthetic
1.1 U3 SA to Vol ratio is important in the limitation of cell size
1 vol 27
6 SA 54
6: 1 SA: VOL 2: 1
The plasma membrane is responsible for import/export in the cell
Metabolic reactions occur on membranes
A larger SA: Vol ratio means the cell can act more efficiently : for every nit of vol that
requires nutrients or produces waste , there is more membrane to serve it
How else is a large SA:Vol ratio a benefit ?
Diffusion pathway are shorter, so more efficient - molecule do not have to travel so far
to get in/ out of the cell , so it takes less time and ( if it is active transport ) energy
Concentration gradient are easier to generate - diffusion more efficient, e.g it takes less
solute to make 10% solution in a 100 ml beaker than a 10l bucket
A large SA: Vol ratio is not always an advantage
Small warm-blooded mammals lose heat very quickly due to their large SA: Vol ratio.
They need to eat almost constantly!
( think about how hungry you get on a cold day )
● Small organisms have the opposite problem of a rapid rate of exchange with the
● Sore minutus ( pygmy shrew ) - eat every 2 hrs to stay alive ( gain amt of heat
needed )
● This is a brief intro to scaling in biological systems . There’re a variety of other
Desert plants would lose water quickly with flat leaves, so they minimise their SA:Vol
ratio in order to conserve water. She plants change their metabolism ( CAM plants ) to
save water
● Cactus ( needle like structure, those r equivalent to their leaves - photosynthesis
- to lose less water )
So how do organisms maximise SA:VOL RATIO
As organisms grow , cell divide two small cells are more efficient than one large cell
This also allows for cell differentiation, specialized faucet and more complex
multicellular life
Cell compartmentalise - they have us membranes to carry out metabolic processes. In
eukaryotes , these are Called organelles
More stuff from ppt / tb
Cell and tissues r specialised for gas or materials exchange will increase their SA to
optimise the transfer of materials e.g microvilli in the small intestine
In summary
- The rate of metabolism of a cell is a function of its mass/vol
- The rate of materials exchange in and out of a cell is functionalists of its SA
- As the cell grows , vol increase faster than sa ( leading to decreased sa:vol ratio )
- I the majolica rate is greater than the rate of exchange of vital material and waste , the
cell will eventually die
- Hence the cell must consequently divide in order to restore a reasonable o viable SA :
Vol and survive
- Cells and tissues specialized for gas or material exchange
1.1 U4 multicellular organism have properties that merely from there iteration of
their cellular component
Volvox aureus - a type of alga, a unicellular organism that lives together in
colonies. Each colony consists of a ball made of protein gel with 500. Or more identical
cells attached to its surface
Altho the cell are cooperating, they are NOT fused to form a single cell mass and so are
not a single organism
Multicellular organism
● Consist of a single mast cells, fused together
● The most intensively research multicellular organism is a worm called
caenorhabditis elegant
○ An adult body is 1mm long and it is made up of exactly 959 cell
● This might seem like a large no. but most multicellular organism have more cells
● There are mil cells in an adult human body and even more in organisms such as
oak trees or a whale
The bigger the multicellular is, the more cells in the body
Caenorhabditis elegans
● Has a mouth, pharynx , intestine and anus
● It is hermaphrodite having both male and female reproductive organs
● One third of is is made of neutrons located at the front end tact one regarded as
the brain
● It does not control how individual cells develop
● The cell cooperative and organise to interact with each other
Emergent properties
Emergent properties the characteristics of the whole organism, the interaction with each
other making it more beneficial for organism rather than acting individually
● Arise form the interaction of component parts
● The whole is greater than the sum of its parts
● Multicellular organism are capable of completing functional that individual cells
could not overtake
Atoms - molecules - cells - tissue - organ- organ system - organism
Since traditionally has taken a reductionist approach to solve problems and developing
System biology uses inductive thinking as it is relied the importance of emergent
properties, whether it be the interaction of genes, enzymes, working together
1.1 U5 specialised tissues can develop by cell differentiation in multicellular
Differentiation : development of cells in different ways to carry out specific functions
● It happens because a different sequence of genes is expressed in the different
cell type
● They develop ideal structure, with the enzymes needed to carry out the
The control of gene expression is the key to development