1.1 Syllabus
U1. Living Organisms are composed of cells
-Cells are smallest unit of life
-Unicellular: Smallest organism (it is 1 cell that contains all characteristics)
-Multicellular: Composed of many cells
So… Cell Theory is:
-Unicellular: Smallest organism (it is 1 cell that contains all characteristics)
-Multicellular: Composed of many cells
- Living cells are surrounded by cell membrane which is semi-permeable
- Contains genetic material that needed for cell activities
- Many reactions are chemical reactions catalyzed by enzymes produced inside the cell
- Cells have own energy release system
So… Cell Theory is:
- All organisms are composed of cells
- All cells originate from a pre-existing cell
- Cell is the basic unit of life
A1. Cell theory exception
1. Striated muscle: It challenges the idea of that cell can have only 1 nucleus-Type of tissues (muscle fibres) that change the position of our body
-Muscle cells (fibres) have more than one nucleus per cell and it is very long
-It’s surrounded by single plasma membrane
2. Aseptate Fungi hyphae : Challenges idea that cell is single unit
-Fungi consists of narrow thread like structure (Hyphae that is composed of chitin)
-Has no cellular partitions
-Multi nucleated and with continuous cytoplasm ( along hyphae that are no end wall or membrane)
3. Giant algae: Grown to be very large-It’s an organism that feed themselves by photosynthesis
-Very large in size but single cells
-Complex in form that consists of 3 anatomical parts
-Muscle cells (fibres) have more than one nucleus per cell and it is very long
-It’s surrounded by single plasma membrane
2. Aseptate Fungi hyphae : Challenges idea that cell is single unit
-Fungi consists of narrow thread like structure (Hyphae that is composed of chitin)
-Has no cellular partitions
-Multi nucleated and with continuous cytoplasm ( along hyphae that are no end wall or membrane)
3. Giant algae: Grown to be very large-It’s an organism that feed themselves by photosynthesis
-Very large in size but single cells
-Complex in form that consists of 3 anatomical parts
U2. Unicellular organisms carry out all functions of life
Metabolism: Living things undertake essential chemical reactions Ex) Respiration
Response: Living things can respond and interact with environment
Homeostasis: Maintain stable internal environment ex) water and pH
Growth: Living things grow or change size and shape
Reproduction: Living things produce offspring asexually or sexually
Excretion: Removal of metabolic waste
Nutrition: Feeding by synthesis of organic molecules or absorption of organic matter
Response: Living things can respond and interact with environment
Homeostasis: Maintain stable internal environment ex) water and pH
Growth: Living things grow or change size and shape
Reproduction: Living things produce offspring asexually or sexually
Excretion: Removal of metabolic waste
Nutrition: Feeding by synthesis of organic molecules or absorption of organic matter
A2. Investigation of function of life in Paramecium and one named photosynthetic unicellular organism
- Paramecium
R: Cilia moves the paramecium in response to changes in environment
H: Contractile Vacuole fill up water and expel through plasma membrane to manage water content with tolerable limits.
G: Consuming and assimilating biomass from food and Paramecium will get larger until it divides. Digested nutrients r absorbed into cytoplasm where they provide energy and materials needed for growth.
R: Nucleus can divide to support cell divisions by mitosis
E: Plasma membrane control exit and entry of substances including expulsion of metabolic waste
N: Food vacuole contain organism that the cell has consumed.
U3. Surface are to volume ration is important in limitation of size
-Plasma membrane is responsible for exit and entry of cell and metabolic reaction occurs in membrane
-For metabolism to continue, substance used in reaction need to be absorbed and waste products must be removed
Surface: Rate at which the cell can take in or send out waste materials
Volume: Amount of food a cell needs, amount of excretions the cell produces. (Rate of gas exchange of material)
→ Efficient removal of waste products: High Surface area and Low volume (Rate of metabolism)
→Large SA:V means faster heat loss and cell can act more efficiently since there is shorter pathways for diffusion. (Don't need to travel far to get in and out of cell)
→ Low SA:V means exchange of materials take longer which reduce efficiency of exchange
→When cell grows, SA:V decreases since rate of gas exchange is too low
So… how to maximize?
→Organisms grow and cell divides= 2small cell are more efficient than 1 big cell
(Allows for cell differentiation, specialized functions and more complex multicellular life)
But… Large SA:VOL x always advantage
-Warm blooded animals: Lose heat quickly so need to eat constantly
-Desert plant lose water quickly with flat leaves= Minimize SA:VOL to conserve water
Ratio too small:
-Takes long time for substances to enter and waste products will be accumulated. -> produced more rapidly than can be excreted
If volume increases faster than SA, cell dies. Therefore SA should be larger than volume
-Cell needs to constantly divide to have suitable SA:Vol ratio
-For metabolism to continue, substance used in reaction need to be absorbed and waste products must be removed
Surface: Rate at which the cell can take in or send out waste materials
Volume: Amount of food a cell needs, amount of excretions the cell produces. (Rate of gas exchange of material)
→ Efficient removal of waste products: High Surface area and Low volume (Rate of metabolism)
→Large SA:V means faster heat loss and cell can act more efficiently since there is shorter pathways for diffusion. (Don't need to travel far to get in and out of cell)
→ Low SA:V means exchange of materials take longer which reduce efficiency of exchange
→When cell grows, SA:V decreases since rate of gas exchange is too low
So… how to maximize?
→Organisms grow and cell divides= 2small cell are more efficient than 1 big cell
(Allows for cell differentiation, specialized functions and more complex multicellular life)
But… Large SA:VOL x always advantage
-Warm blooded animals: Lose heat quickly so need to eat constantly
-Desert plant lose water quickly with flat leaves= Minimize SA:VOL to conserve water
Ratio too small:
-Takes long time for substances to enter and waste products will be accumulated. -> produced more rapidly than can be excreted
If volume increases faster than SA, cell dies. Therefore SA should be larger than volume
-Cell needs to constantly divide to have suitable SA:Vol ratio
U4. Multicellular organisms have properties that emerge due to the interaction of their cellular components
Emergent properties: Arise when interaction of individual component produces new functions
Multicellular able to complete functions that single cell can’t due to interaction between cells producing new function.
Atom → Molecule → Cell → Tissue → Organ → Organ system → Organism
(Each level arises emergent properties)
Multicellular able to complete functions that single cell can’t due to interaction between cells producing new function.
Atom → Molecule → Cell → Tissue → Organ → Organ system → Organism
(Each level arises emergent properties)
U5. Specialized tissues can develop by cell differentiation in multicellular organism
-All specialized cells and organs are constructed from them have developed as a result of differentiation.
-Different cell performs different functions in multicellular organism.
-Tissue: Group of cells that specializes in same way to perform same function
-Differentiation: Develop of cells in different ways to carry out specific function
-Specialization of cell functions: Each cell in multicellular organism has its own function, which is defined by the expressed genes in that cell.
-Different cell performs different functions in multicellular organism.
-Tissue: Group of cells that specializes in same way to perform same function
-Differentiation: Develop of cells in different ways to carry out specific function
-Specialization of cell functions: Each cell in multicellular organism has its own function, which is defined by the expressed genes in that cell.
U6. Differentiation involves the expression of some genes and not others in cell’s genome
-Genome: Entire set of genes of organisms.
-All cell organisms share an identical genome.
→each cell contains entire set of genetic instructions for that organism
-Different types of cell in multicellular organisms but have identical genes
-Cells do not just have genes with instruction but have genes needed to specialize in possible ways
SO.. Why do cell differentiation happen?
-All cell organisms share an identical genome.
→each cell contains entire set of genetic instructions for that organism
-Different types of cell in multicellular organisms but have identical genes
-Cells do not just have genes with instruction but have genes needed to specialize in possible ways
SO.. Why do cell differentiation happen?
- Different sequence of genes expressed in different cell types.
- Control of gene expression = Key to develop
U7. The capacity of stem cells (unspecialized cells) to divide and differentiate along different pathways is necessary in embryonic development. It also make stem cells suitable for therapeutic uses.
Stem cells differentiate and become a specific cell.
2. Potency: They can differentiate into specialized cell types
-Stem cells are necessary for embryonic development as they are an undifferentiated cell source from which all other cell types may be derived.
Related Question:
Q) Describe the characteristics of stem cells that make them potentially useful in medicine
Answer: Stem cells have capacity to divide and can be used to produce larger number of identical cells. It can be used to repair damaged tissue. Stem cells are undifferentiated. It can be differentiate in different ways (Pluripotent/ Totipotent). It can be used to form a variety of different tissues. It's used in medical research such as leukaemia (Cancer of White Blood Cells)
- Capacity to continuously divide and to differentiate along different pathways.
- Found in most human tissues (skin, liver, bone marrow)
- Give some human tissues considerable powers of regeneration and repair though it does not have as great capacity to differentiate in different ways as embryonic stem cells.
- Can divide continuously to produce copious quantities of new cells and it is useful for growth of tissues/replacement if cells that have been damaged.
2. Potency: They can differentiate into specialized cell types
-Stem cells are necessary for embryonic development as they are an undifferentiated cell source from which all other cell types may be derived.
Related Question:
Q) Describe the characteristics of stem cells that make them potentially useful in medicine
Answer: Stem cells have capacity to divide and can be used to produce larger number of identical cells. It can be used to repair damaged tissue. Stem cells are undifferentiated. It can be differentiate in different ways (Pluripotent/ Totipotent). It can be used to form a variety of different tissues. It's used in medical research such as leukaemia (Cancer of White Blood Cells)
A3.Use of stem cells to treat Stargardt’s disease and one other named condition
- Stargardt’s disease
-It is a degenerative disease of the eye (Retina cells)
-Most cases due to recessive mutation of a gene
=Cause membrane protein used for active transport in Retina cells to malfunction
-Vision becomes progressively worse
-Developed methods for making stem cells developed into retina cells.
Related Question:
Q) Use of human embryonic stem cells to treat Stargardt's disease:
Answer: An inherited form of degeneration of retinal layer, which is a eye genetic disorder. Stem cells can provide healthy retinal cells into the retina that helps to restore vision in animal trials.
- Leukaemia
-A patient with leukaemia is irradiated and given chemotherapy to kill all cancerous white blood cells. The killed cells are then replaced by the matching cord blood cells which are able to differentiate into all kinds of white blood cells in the patient
A4. Ethics of therapeutic use of stem cells
Stem cells can be derived from one of three sources:
-Embryos (may be specially created by therapeutic cloning)
-Umbilical cord blood or placenta of a new-born baby
-Certain adult tissues like the bone marrow (cells are not pluripotent)
The ethical considerations associated with the therapeutic use of stem cells will depend on the source
-Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application
-Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access
-The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism
-Embryos (may be specially created by therapeutic cloning)
-Umbilical cord blood or placenta of a new-born baby
-Certain adult tissues like the bone marrow (cells are not pluripotent)
The ethical considerations associated with the therapeutic use of stem cells will depend on the source
-Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application
-Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access
-The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism
S1. Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs.
Formula:
Image of cell= Real cell size x Magnification
Real cell size: Image of cell / Magnification
Size of Cells (Smaller to Larger Size)
Molecules < Cell membrane (10nm) < Virus (100nm) < Prokaryotes (1um) < Organelles (10um) < Eukaryotes (100um)
Image of cell= Real cell size x Magnification
Real cell size: Image of cell / Magnification
Size of Cells (Smaller to Larger Size)
Molecules < Cell membrane (10nm) < Virus (100nm) < Prokaryotes (1um) < Organelles (10um) < Eukaryotes (100um)