topic 1.1- introduction to cells Flashcards
Define cell theory
all living organisms are composed of cells (the basic structural, functional and organisational units).
State and explain 4 features common to all cells
- cell membrane- to separate the cell from it’s surroundings
- genetic material that can be passed on (excluding erythrocytes)
- enzymes- to catalyse reactions within the cell
- energy release system (eg respiration)
State 3 atypical examples of cell theory
- striated muscle
- giant algae
- aseptate fungal hyphae
explain how a striated muscle fibre (SMF) does not conform to standard cell theory
muscle cells fuse, forming SMFs that are very long
=> fibres have multiple nuclei despite being surrounded by a single, continuous plasma membrane.
(challenges idea that cells always function as autonomous units)
explain how aseptate fungal hyphae do not conform to standard cell theory
fungi may have hyphae (filamentous structures), which are separated into cells by septa (internal walls)
=> some fungi not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae
(challenges idea that living structures are composed of discrete cells)
explain how giant algae do not conform to standard cell theory
certain species of unicellular algae may grow to very large sizes
(challenges idea that larger organisms are always made up of many microscopic cells) up to 100 mm in length
give an example of a giant unicellular algae
acetabularia, which may exceed 7cm in length
explain why the ultrastructure of a unicellular organism may be more complex than an individual cell in a multicellular organism
- unicellular must be able to carry out all the functions of life in a single cell.
- multicellular can carry out different functions in different parts of body.
give a eukaryotic and prokaryotic example of a unicellular organism
eukaryotic- amoeba
prokaryotic- s. cervisiae (baker’s yeast)
state the 7 functions of life
metabolism
response
nutrition
excretion
reproduction
growth
homeostasis
homeostasis
the maintenance of a constant, stable environment to keep conditions inside the organism within tolerable limits
growth
irreversible increase in size
reproduction
production of offspring, either sexually or asexually
nutrition
obtaining food to provide energy and materials needed for growth
response
ability to react to changes in the environment
metabolism
chemical reactions inside the cell
excretion
removal of waste products of metabolic reactions
why is size often limited in unicellular organisms?
- surface area affects the rate at which materials enter and leave the cell
- volume affects the rate at which materials are used and produced by the cell
- the surface area to volume ratio affects the rate of metabolism in a cell
- the bigger the cell, the smaller the SA ratio is
- cells having a low SA ratio cannot exchange materials fast enough
what will happen if the SA:VOL ratio of a cell is too small? (3)
- substances will not enter the cell quickly enough
- waste products will accumulate (produced more rapidly than excreted)
- cells may overheat as metabolism produces heat faster than is lost over cell’s surface
what is an emergent property?
a property which a collection or complex system has, but which the individual members do not have, as it arises from the interactions of those individual components
what does an emergent property arise from?
the interaction of cellular components in an organism.
give 3 examples of emergent properties
cells form tissues, tissues form organs, organs form organ systems
what type of organism is paramecium and where does it live
- unicellular eukaryote
- freshwater environments
how does paramecium provide energy for itself?
it is a heterotroph (eats smaller unicellular organisms in order to obtain energy/matter).
main 6 organelles of paramecium
nucleus
cell membrane
cytoplasm
cilia
contractile vacuoles
food vacuoles
paramecium- nucleus
can divide by mitosis to produce the two nuclei that are needed when the cell reproduces (mostly asexually)
paramecium- cell membrane
controls movement of substances/chemicals into and out of cell
paramecium- cytoplasm
contains enzymes that catalyse metabolic reactions, including respiration
paramecium- cilia
- beating of the cilia moves cell through water
- controlled by cell; moves in response to changes in environment
paramecium- food vacuoles
contain smaller organisms that have been consumed (gradually digested + nutrients absorbed into cytoplasm)
paramecium- contractile vacuoles
homeostasis:
- located at each end of cell
- fill up with water from inside the cell then expel excess through plasma membrane.
what type of organism is chlamydomonas and where does it live?
- unicellular eukaryote
- soil, freshwater, oceans, snow
how does chlamydomonas provide energy for itself?
autotroph- can photosynthesise
main 8 organelles of chlamydomonas
nucleus
cytoplasm
cell wall
cell membrane
chloroplasts
flagella
eyespot
contractile vacuoles
chlamydomonas- nucleus
- asexual reproduction: nucleus can divide by mitosis to produce 2 nuclei
- sexual reproduction: nuclei can fuse + divide to carry out sexual reproduction
chlamydomonas- cytoplasm
contains enzymes that catalyse metabolic reactions, including respiration
chlamydomonas- cell wall/membrane
- wall is freely permeable
- membrane controls what chemicals enter and leave
chlamydomonas- chloroplasts
- where photosynthesis occurs
- contains enzymes
- in dark, carbon compounds can be absorbed from other organisms via the cell membrane
chlamydomonas- flagella
the beating of the two flagella moves the chlamydomonas through the water it lives in
chlamydomonas- eyespot
light sensitive; allows cell to sense where brightest light is and respond by swimming towards it
chlamydomonas- contractile vacuoles
homeostasis:
- located at base of flagella
- fill up with water from inside the cell then expel excess through plasma membrane.
how do specialised tissues develop in multicellular organisms and why is this process important?
by cell differentiation;
allows them to carry out their role more efficiently than if they had many different roles.
define cell differentiation in terms of gene expression
differentiation involves the expression of some genes and not others in a cell’s genome.
give two key properties of stem cells.
self renewal; can continuously divide and replicate.
potency; have the capacity to differentiate into different specialised cell types.
give 3 places where stem cells can be found in the adult body
bone marrow, skin, liver
give 3 different types of stem cells
- embryonic
- cord blood
- adult
describe the growth potential of embryonic stem cells
almost unlimited growth potential; can differentiate into any cell type in the body.
describe the growth potential of cord blood stem cells
limited capacity to differentiate into different cell types (only naturally develop into blood cells)
describe the growth potential of adult stem cells
limited capacity to differentiate into different cell types.
give 1 pro of embryonic stem cells
less chance of genetic damage due to the accumulation of mutations than with adult stem cells.
give 3 cons of embryonic stem cells
- more risk of becoming tumour cells than ASC
- likely to be genetically different from patient
- removal of cells from embryo kills it
give 3 pros of cord blood stem cells
- easily obtained and stored
- fully compatible with tissues of adult that grows from the baby (no rejection probs)
- umbilical cord discarded either way
give 1 con of cord blood stem cells
- limited quantities of stem cells from one baby’s cord
give 3 pros of adult stem cells
- less chance of malignant tumours developing than from ESC
- fully compatible with the adult’s tissues (no rejection probs)
- removal does not kill adult
give 1 con of adult stem cells
- difficult to obtain as there are very few of them/buried deep in tissues. 0
give 2 examples of diseases that can be treated using stem cells
Stargardt’s disease
Leukaemia
explain the use of stem cells to treat Stargardt’s disease
Embryonic cells developed into retina cell and then injected into the eye to improve vision.
explain the use of stem cells to treat leukaemia
- stem cells extracted from bone marrow
- chemotherapy given, bone marrow loses ability to produce blood cells.
- stem cells returned to body and start to reproduce red and white blood cells.
m -> mm
x1000
mm -> μm
x1000
μm -> nm
x1000
give the equation used with microscopes.
size of image = magnification x actual size
