1.1 Introduction to Cells Flashcards
What is cell theory? and what are common characteristics of living cells?
The cell theory states that
- cells are the fundemental builidng blocks of all living organisms
- cells are the smallest unit of life
- all cells come from preexisting cells
common features of cells
- cells have membranes seperating the cell contents from everything else outside
- cells contain genetic material which store the instructions needed for cell’s activity
- cells undergo chemical reactions catalysed by enzymes produced inside the cell
- cells have their own energy release system which powers a cell’s activity
what are three atypical examples of cell theory
STRIATED MUSCLE
the tissue we use to change the position of our body
similar
- has a membrane
- formed from preexisting cells
- own genetic material
- own energy release system
different
- larger than most animal cells 930 mm vs 0.3mm)
- several hundred nuclei
GIANT ALGAE
organisms that feed on photosynthesis and store genes inside nuclei, simpler than plants in sturcture and organisation. Vast number of algae and basis of many food chains.
differences
- ACETABULARIA has one nucleus and is 100mm long and unicellular. would expect it to be multicellular
AESEPTATE FUNGAL HYPHAE
fungi have narrow thread like hyphae structures which are usually fulffy and white in colour
similar
- cell membrane and cell wall
- in some fungi hyphae divided into cell like sections by cross walls called septa
different
- in aseptate fungi so no septa and uninterrupted tube like structure with many nuclei
what are the functions of life
- metabolism
- response
- growth - irreversible
- reproduction
- excretion
- nutrition
- homeostasis
some move other are fixed or drift so movement is not a function of life
examples and characteristics of unicellular organisms and how complex they are
e.g. PARAMECIUM and CHLAMYDOMONAS
organisms that consist of only one cell are more complicated because they need to carry out all the functions of life in just one cell
PARAMECIUM - can be cultured easily or found if yoiu centrifuge pond water
- nucleus can divide to produce extra nuclei needed when cell reproduces, often asexual
- food vacule contains smaller organisms the paramecium has consumed, gradually digested, broken down into cytoplasm for energy and materials for growth
- cell membrane controls what chemicals enter and leave
- contractile vacuole on each end of cell fill up with water and then expel it thorugh plasma to keep cells water content tolerable
- metabolic reactions take place in cytoplasm e.g. respiration, enzymes in cytoplasm catalyse these reactions
- beating of cilia moves paramecium through water and this can be controlled by cell in response to changing environment - movement is the function of life here
CHLAMYDOMONAS
unicellular algae that lives in soil and freshwater, used widely in research, green and carries out photosynthesis, not a true plant as cell wall is not made of cellulose
- nucleus of cell can divide to produce genetically identical nuclei for asexual reporduction
- metabolism takes place inside cytoplasm with enzymes to speed up reaction
- cell wall is permeable and membrane inside controls what goes in and out
- contractile vacuole at base of flagella fill up with water and expel through the plasma membrane to keep water in tolerable limits
- photosynthesis occurs in cholorplasts in cytoplasm, also CO2 can be converted into compounds needed for growth but in dark carbon compounds from other organisms are absorbed through cell membrane if available
- beating of two flagella moves it through water, eyespot allows teh cell to sense where the brightest light is and respond by swimming towards it
surface area to volume ratio effects and examples and role of heat in cells
- rate of exchange across cell membrane depends on SA/V
- rate of metabolism is proportionate to volume because for metabolism to continue waste products must be removed and nutrients supplied
- heatloss > heat production in an INDIVIDUAL cell to avoid overheating
cells need to effectively release heat to the body to avoid overheating and combustion, this limits cell size
examples of good SA/V ratios
- red blood cells
- villi
- root hair cells
what are multicellular organisms and how do we differentiate them from unicellular?
multicellular organisms are organisms that have fused together to form a single mass.
example some unicellular organisms e.g. VolVox aureus consist of colonies, which are balls of protein gel with 500 unicellular cells attached to them, allthough the cells are co-operating they are not a single mass so their are not multicelluar.
what is the intesely research worm which shows multicellular organisms?
Caenorhabditis elegnas
- 1 mm long and has 959 cells with in it
- lives in decomposing organic matter feeding on the bacteria that cause decomposition
- has a mouth, pharynx, intestine and anus and is hermaphrodite, almost 1/3 of cells are neurons
- although the brain co-ordinates response of to the worms environement as it is multicellular it is actually a co-operative group with no cell acting as a leader or supervisor
- the characteristics of the whole organism (e.g. the fact tha it is alive) are known as emergent properties
- emergent properties arise from the interation of the component parts of a complex structure - the whole is greater than the sum of its parts
how is cell differentiation used in multicellular organisms?
this is used for division of labour as similar cells clump together to form tissue.
cells can carry out their role more efficiently than if they had many roles.
we humans have 220 distinictly differentiatied types of cells
how are genes used in differentiation? - and an example
cells do not just have the genes with the instructions they need they have all the genes needed to specialise any cells.
In differentiation the pattern of expression of these genes changes as some are switched on and a different sequence is expressed. - roughly 25 000 genes but only 12500 every switched on at one moment.
Axel and Buck
a large family of genes in carry the receptors for odorants, called olfactory receptor cells. each of the cells expresses just one gene and makes on type of receptor detect one type of odorant.
stem cells and their importance
the capactiy of stem cells to divide and differentiate along different pathways is necessary for embryonic development. It also makes stem cells suitable for therapeutic uses (provide therapy for diseases and other health problems)
a zygote is made of a single stem cell that can then divide into anything, origin of all cells, unifying point
cells on the outside of the blastocyte become the placenta, inside are the stem cells
properties of stem cells
- can divide again and produce copious quantities of new cells and are therefore useful for growth of new tissues and to replace damaged cells
- stem cells are not fully differentiated
levels of differentiation
- totipotent
- pluripotent
- multipotent
- unipotent
as stem cells divide they become more and more differentiated and how less pathways availible to them. However some stem cells remain in the body e.g. bone marrow, liver, skin , brain, heart
what are embyronic stem cells useful for?
therapeutic
- can produce regenerative tissue e.g. skin for people with burns
- could heal diseases e.g. type 1 diabetes where a particular cell type is lost or is malfunctioning
- could even grow whole organs
non-therapeutic
- produce large quanitities of striated muscle fibres, or meat
use of stem cells in an eye condition
STARGARDTS MACULAR DYSTROPHY
it is a genetic disease that is recessive (on ABCA4 gene) and develops in children.
causes a membrane protein used for active transport in retina cells to malfunction so photoreceptive cells in the retina degenerate and (as these detect light) vision becomes progressively worse –> can become blind
researchers have developed embryonic stem cells into these retina cells. in an animal trial on mice when the stem cells were injected the stem cells moved to the retina and attached themselves. They remained there and improved the mice’s vision.
Then researchers injected 50 000 such cells on a human trial (lady in her 50s) and again the cells attach, remained attached and vision improved with no harmful side effects.
use of stem cells in a blood condition
leukemia is a type of cancer where a mutation occurs in genes that control cell division. more then 1/4 of a million cases diagnosed every year and over 200 000 deaths.
production of abnormally large white blood cells, but no lump or tumour develops.
normal levels of wbc 4 000-11 000 per mm3 of blood
in leukemia 30 000 or more
procedure:
- needle inserted into large bone (pelvis) and fluid removed
- stem cells extracted from fluid and frozen (adult stem cells)
- chemotherapy is used to kill the cancerous cells in the bone marrow, kills all stem cells
- stem cells returned to patients body
- in many cases leukemia completely cured
compare different sources of stem cells
embryonic stem cells
- almost unlimited growth potential (totipotent)
- more risk of becoming a tumour cell or teratoma which contain different tissue types
- less chance of genetic damage due to accumulation of mutations
- likely to be genetically different so higher risk of rejections
- removal of cells kills embryo (which has 4-16 cells at that point)
cord blood stem cells
- easy to obtain and store, commercial collection and storage availible (is expensive however), umbilcal cord discarded anyway
- fully compatible with tissue of adut that grows from baby so no rejection
- limited quantity in cord blood
- limited capacity to differentiate into different cell types, only naturally blood cells, but research may change this
adult stem cell
- difficult to obtain as very few and are buried very deep in the tissue and some tissue has few stem cells
- less growth potential (and only mutlipotent)
- consensually obtained and does not involve death of an embryo
- less chance of malignant tumour forming due to less growth potential
- higher risk of accumulated mutations
- fully compatible , no rejection
controversy regarding stem cell research
death of embryo? when does life begin (fertilisation, heartbeat, brain activity, birth) ? is one life more valuable?
is IVF moral as the embryos would never be intended for baby becoming anyway but may exploit vulnerable people e.g. college students if money is offered
have potential to treat and cure millions of diseases and reduce suffering
what is the formula involving magnification, orginial size and actual size and what are conversions for units?
mm - 000 - micrometer - 000- nanometer
calibrating eyepieces etc.
to get max magnification multiply to the magnification of the eyepeice adn the objective lense together
as magnification increases the value of a unit decreases
you need to recallibrate the eyepiece graticule scale using a stage micrometer each time you use it
to callibrate say: 100 eyepiece units = 20 micrometer units = 200 micrometer
therefore 1 eyepiece unit is 2 micrometers
