1.1 Cell Introduction Flashcards
what are the principles of cell theory? (3)
- all living things are composed of cells
- the cell is the smallest unit of life
- cells only arise from pre-existing cells
what are the 3 caveats to the cell theory?
- striated muscle fibres
- aseptate fungal hyphae
- giant algae
why is striated muscle fibre a caveat to cell theory? (2)
- muscle cells fuse to form fibres that may be very long
- they have multiple nuclei despite being surrounded by a single, continuous plasma membrane
how do striated muscles cells challenge the cell theory?
challenge the idea that cells always function as autonomous unit
why is aseptate fungal hyphae a caveat to cell theory? (2)
- fungi may have filamentous structures called hyphae which are separated into cells by internal walls called septa
- some fungi are not partitioned by septa and have continuous cytoplasm along the length of the hyphae
how do aseptate fungal hyphae challenge the cell theory?
challenge the idea that living structures are composed of discrete cells
why is giant algae a caveat to cell theory?
they may grow very large
how do giant algae challenge cell theory?
challenge that large organisms are always made of many microscopic cells
what are 7 basic functions integral to survival?
- metabolism- living things undertake essential chemical reactions
- reproduction - living things produce offspring (sexually/asexually)
- sensitivity - living things are responsive to internal and external stimuli
- homeostasis - living things maintain a stable internal environment
- excretion - living things exhibit the removal of waste products
- nutrition - living things exchange materials and gases w/ environment
- growth - living things can move and change shape or size
why must unicellular organisms carry out all functions of life?
they are composed of a single cell
what are 2 examples of unicellular organisms?
paramecium
scenedesmus
how does paramecium carry out all of its cell functions? (6)
- surrounded by small hairs called cilia allow it to move (responsiveness)
- engulf food via specialised membranous feeding groove called a cytostome (nutrition)
- food particles are enclosed within small vacuole that contain enzymes for digestion (metabolism)
- solid wastes are removed via anal pore, liquid waste is pumped out via contractile vacuoles (excretion)
- essential gases enter and exit via diffusion (homeostasis)
- divide asexually (fission) although horizontal gene transfer can occur via conjugation (reproduction)
how does scedesmus carry out all of its cell functions? (4)
- exchange gases and other essential materials vis diffusion (nutrition/excretion)
- chlorophyll pigments allow organic molecules to be produced via photosynthesis (metabolism)
- daughter cells form as non-motile autospores via internal asexual division of the parent cells (reproduction)
- scedesmus may exist as unicells/ form colonies for protection (responsive)
how is the rate of metabolism of a cell found?
mass/volume (larger cells need more energy to sustain essential functions)
how does the rate of material exchange found?
surface area (large membrane surface equates to more material movement)
How does how cell growth influence the SA:VOL ratio?
as the cell grows, volume increases faster than surface area, leading to a decreased SA:VOL ratio
what will occur if the metabolic rate exceeds the rate of exchange of vital materials and wastes and the consequence? (2)
- the cell will eventually die
- growing cells tend to divide and remain small in order to maintain a high SA:VOL ratio suitable for survival
what are two types of cells or tissues that are specialised for gas/ material exchange will increase their surface area to optimise material transfer?
vili
alveoli
how do villi specialise to increase their surface area to optimise material transfer?
- have ruffled structures to increase the surface area of the inner lining
how do alveoli specialise to increase their surface area to optimise material transfer?
- microvilli -> membranous extension which increases the total membrane surface
how do you calculate magnification/actual size/ image size?
I = AxM
what are advantages of light microscopes? (3)
- viewed in natural colour
- cheap
- easy to access
how do emergent properties arise?
when the interaction of individual component produce new functions
why can multicellular organisms complete functions that unicellular organisms can’t
due to the collective actions of individual cells combining to create new synergistic effects
what is the order of multicellular organisms?
cells grouped to form tissues
multiple tissues to form organs
organs that interact form organ systems
organ systems that collectively carry out life functions of complete organism
what is differentiation?
the process during development whereby newly formed cells become more specialised and distinct from one another as they mature
what do all organisms share?
share identical genome
what causes differentiation to occur>
the activation of different genes within a given cell by chemical signals
what is DNA packaged with to form chromatin?
proteins
what are active genes usually packaged in which is accessible to transcriptional machinery?
euchromatin
what are inactive genes are typically packaged in a more condensed form?
heterochromatin (saves space, not transcribed)
how will different regions of DNA packaged as euchromatin and heterochromatin?
according to their specific function
what 2 key qualities do unspecialised cells have?
- self-renewal (can continuously divide and replicate)
- potency (can differentiate into specialised cell types)
what are the 4 types of stem cells?
- totipotent - form any cell type and extra-embryonic (placental) tissue (eg. zygote)
- pluripotent - can form any cell type (eg. embryonic stem cells)
- multipotent - can differentiate into a number of closely related cell types (eg. haematopoetic adult stem cells)
- unipotent - cannot differentiate but not capable of self-renewal (eg. progenitor cells, muscle stem cells)
why can stem cells be used for viable therapeutic options?
cells that are not capable of self-renewal cannot be regenerated or replaced when these tissues become damaged, stem cells can be used
what is the process of stem cell used to replace damaged or diseased cells with healthy functioning ones? (4)
- use of biochemical solutions to trigger the differentiation of stem cells into desired cell type
- surgical implantation of cells into the patient’s own tissues
- suppression of host immune system to prevent rejection of cells (if stem cells are from foreign source)
- careful monitoring of new cells to ensure they do not become cancerous
what are 3 examples of stem cell therapy?
stargardt’s disease
parkinson’s disease
leukemia
paraplegia
diabetes
burn victims
what is stargardt’s disease and how can stem cells be used?(3)
- inherited juvenile macular degeneration cause vision loss to the point of blindness
- caused by gene muation that imparis energy transport in retinal photoreceptor
- treated by replacing dead cells in retina w/ functioning ones derived from stem cells
what is parkinson’s disease and how can stem cells be used?(3)
- a degenerative disorder of CNS caused by death of dopamine-secreting cells in midbrain
- dopamine= neurotransmitter responsible for transmitting signals
- treated by replacing dead nerve cells with living, dopamine-producing ones
what are 4 other therapeutic examples and how they can be treated? (4)
- leukemia - bone marrow transplant for cancer patients who are immunocompromised as a result of chemotherapy
- paraplegia - repair damage caused by spinal injuries to enable paralysed victims to regain movement
- diabetes - replace non-functioning islet cells w/ those capable of producing insulin in type I diabetics
- burn victims - graft new skin cells to replace damaged tissues
what 3 things placed stem cells be derived from?
embryos (may be specially created by therapeutic cloning)
umbilical cord blood/ placenta or newborn babies
certain adult tissues like bone marrow (not pluripotent)
what are ethical considerations associated w/ therapeutic use of stem cells of the source? (3)
- using multipotent adult tissues may be effective for certain conditions but 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
- greatest yield of pluripotent stem cells come from embryos but requires destruction of potential living organism
what are 2 artificial stem cell techniques?
somatic cell nuclear transfer (SCNT)
nuclear reprogramming
what is somatic cell nuclear transfer (SCNT)?(2)
- involves the creating of embryonic clones by fusing a diploid nucleus w/ enucleated egg cells (therapeutic cloning)
- more embryos are created by the process, raising ethical concerns about exigency of excess embryos
what is nuclear reprogramming? (2)
- induce a change in the gene expression profile of a cell in order to transform it into a different cell type (transdifferentiation)
- involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences
