1.1 Introduction to cells Flashcards
What are the three principles of cell theory?
All living things are composed of cells
The cell is the smallest unit of life
What are the three exceptions to cell theory?
Striated muscle fibres
Aseptate fungal hyphae
Giant algae
What theory does striated muscle fibres challenge?
That cells always function as autonomous units
Why are striated muscle fibres an exception to cell theory?
They fuse to form very long fibres and have multiple nuclei
What cell theory idea does aseptate fungal hyphae challenge?
That living structures are composed of discrete cells
How are aseptate fungal hyphae an exception to cell theory?
They are not partitioned by septa and have a continuous cytoplasm
What idea of cell theory does giant algae challenge?
That larger organisms are made up of many cells
How does giant algae break cell theory?
Unicellular algae can grow up to 7cm in length
What are the 7 functions of survival? Mr Sheng
Metabolism
Reproduction
Sensitivity
Homeostasis
Excretion
Nutrition
Growth
What is metabolism?
Living things undertake essential chemical reactions
What is reproduction?
Living things produce offspring either sexually or asexually
What is sensitivity?
Living things are responsive to interval and external stimuli
What is homeostasis?
Living things maintain a stable internal environment
What is excretion?
Living things exhibit the removal of waste products
What is nutrition?
Living things exchange materials and gases with the environment
What is growth?
Living things can move and change shape or size
How many life functions must unicellular organisms be able to carry out?
All of them
How does paramecia do responsiveness?
They are surrounded by cilia which allow it to move
How does paramecia do nutrition?
Engulfs food via a cytosome
How does paramecium do metabolism?
Food particles are enclosed within small vacuoles that contain enzymes for digestion
How does paramecium do excretion?
Solid wastes are removed by an anal pore whilst liquid wastes are pumped out by contractile vacuoles
How does paramecium do homeostatsis?
Essential gases enter and exit the cell via diffusion
How does paramecium do reproduction?
They divide assexually although horizontal gene transfer can occur via conjugation
How does scenedesmus do nutrition/excretion?
They exchange gases and other essential materials via diffusion
How does scenedesmus do metabolism?
Chlorophyll pigments allow organic molecules to be produced via photosynthesis
How does scenedesmus do reproduction?
Daughter cells form as non-motile autospores via the internal asexual division of the parent cell
How does scenedesmus do responsiveness?
They may exist as unicells or form colonies for protection
What do cells need to produce to survive?
Chemical energy
What does the production of chemical energy require?
The exchange of materials with the environment
What is the rate of metabolism of a cell?
A function of its mass/ volume
What do larger cells need more of to sustain essential functions?
Energy
What is the rate of material exchange a function of?
Its surface area
What does large membrane surface equate to more..?
Material movement
As a cell grows what increases faster?
Volume increases faster than surface area
What will happen if the metabolic rate exceeds the rate of exchange of vital materials and wastes?
The cell will eventually die due to to a low SA:Vol ratio
What does the increased volume and slower increase of surface area lead to?
Decreasing SA:Vol ratio
What do cells have to do in order to maintain a high SA:Vol ratio?
Divide and remain small
What type of cells and tissues will increase their surface area and why?
Cells and tissues specialised for gas/material exchange to optimise material transfer
What does the intestinal tissue of the digestive tract do to increase the surface area of the inner lining?
Form a ruffled structure
What do alveoli in the lungs have to increase the total membrane surface?
They have membranous extensions called microvilli
What is the formula for calculating magnification?
Magnification = image size / actual size
M=I/A
How do you measure image size?
With a ruler
How do you measure actual size?
In accordance to the scale bar
What is the formula to calculate the actual size of a magnified specimen?
Actual size = Image size / magnification
What do light microscopes use to magnify images of mounted specimens?
Visible light and a combination of lenses
How can living specimens be viewed in light microscopes?
In their natural colour
When would a living specimen not be in their natural colour in a light microscope?
If a stain is applied to see specific structures
When drawing microscopic structures what three conventions should be followed?
Title of the specimen
A magnification or scale
Structures should be labelled
When do emergent properties arise?
When the interaction of individual component produce new functions
Why can multicellular organisms complete functions that unicellular organisms can not?
Due to the collective actions of individual cells combining to create new synergistic effects
What is the chain of organisation of multicellular organisms?
Cells
Tissues
Organ
System
Organism
What do cells grouped together form?
Tissues
What are organs formed of?
The functional grouping of multiple tissues
What will organs that interact form?
Organ systems capable of carrying out specific body functions
What do organ systems do?
Collectively carry out the life functions of the complete organism
What is differentiation?
The process during development where newly formed cells become more specialised and distinct form one another as they mature
What do all cells of an organism share?
An identical genome
What does each cell contain?
The entire set of genetic instructions for that organism
What will cause a cell to differentiate?
The activation of different genes within a given cell by chemical signals
What is packaged in the nucleus of a eukaryotic cell?
DNA with proteins to form chromatin
How are active genes usually packaged?
In an expanded form called euchromatin
How are inactive genes usually packaged?
In a condensed form called heterochromatin
Which type of gene packing is accessible to be transcribed?
Euchromatin
What will differentiated cells have different regions of?
DNA packaged as euchromatin and heterochromatin in accordance to their specific function
What does a cell lose when it differentiates and becomes specialied?
The capacity to form alternative cell types
What are the two key qualities of stem cells?
Self renewal and potency
What are stem cells?
Unspecialised cells with key qualities
What does self renewal mean?
They can continuously divide and replicate
What does potency mean?
They have the capacity to differentiate into specialised cell types
What are the four main types of stem cells?
Totipotent
Pluripotent
Multipotent
Unipotent
What is a totipotent stem cell?
Can form any cell type as well as extra-embryonic tissue
What is pluripotent stem cells?
Can form any cell type
What is a multipotent stem cell?
They can differentiate into a number of closely related cell types
What is a unipotent stem cell
They can not differentiate but acn self renew
Why are stem cells necessary for embryonic development?
As they are an undifferentiated cell source from where all other cell types can be derived
What are considered to be non-stem cells?
Cell types that are not capable of self-renewal
Why have stem cells become a viable therapeutic option when tissues become damaged?
As non-stem cells cannot be regenerated or replaced
What can stem cells be used to do?
Replace damaged/diseased cells with health ones
What are the four thing using stem cell process require?
- surgical implantation into the tissue
Suppression of host immune system to prevent rejection of cells
Careful monitoring of new cells
use of biochemical solutions to trigger stem cells into desired cell type
What is stargardts disease?
Inherited form of juvenile macular degeneration causing vision loss to the point of blindness
What is stargardts disease caused by?
A gene mutation that impairs energy transport in retinal photoreceptor cells
How is stargardts disease treated?
By replacing dead cells in the retina with functioning ones from stem cells
What is parkinsons disease?
A degenerative disorder of the central nervous system caused by the death of dopamine secreting cells in the midbrain
What do individuals with parkinsons typically exhibit?
Tremors, rigidity, postural instability and slowness of movement
How is parkinsons disease treated?
By replacing dead nerve cells with living dopamine producing ones
How are burn victims treated with stem cells?
Graft new skin cells to replace damaged tissue
How is type 1 diabetes treated with stem cells?
Replace non functioning islet cells with those capable of making insulin
How is paraplegia treated with stem cells?
Repair damage caused by spinal injuries to enable paralysed victims to regain movement
How is leukemia treated with stem cells?
Bone marrow transplants for those who are immunocompromised as a result of chemotherapy
What are the three sources stem cells can be derived from?
Embryos
Umbilical cords/placenta
Certain adult tissues
Whilst using multipotent adult tissue may be effective for certain conditions what is its limitations?
Its scope of application
What is the problem with stem cells derived from umbilical cord blood?
They need to be stored and preserved at a cost which raises issues of availability and access
What is the argument against using embryos?
It requires the destruction of a potential living organism
What are the two artificial stem cell techniques?
Somatic cell nuclear transfer and nuclear reprogamming
What is somatic cell nuclear transfer?
Involves the creation of embryonic clones by fusing a diploid nucleus with an enucleated egg cell
What is the problem with somatic cell nuclear transfer?
More embryos are created than needed which raises concerns about the exigency of excess embryos
What is nuclear reprogramming?
Induces a change in the gene expression profile of a cell in order to transform it into a different cell type
What are the disadvantages of nuclear reprogramming?
They is oncogenic retroviruses and transgenes which increases the risk of health consequences
