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C1.1 Introduction to Cells
Cell Theory:
1. organisms are made of more than 1 cells
2. the cell is the basic unit structure of organisms
3. cells come from pre-existent cells
Exceptions:
● Fungal Hyphae Cells: multi-nucleated and continuous cytoplasm
● Large Algae: large and unicellular
● Striated muscle: multi-nucleated, long cells, and 1 continuous plasma membrane
Functions:
Metabolism - chemical reactions inside the cell
Response - reactions given to stimuli to help survival
Sensitivity - measure for how strong a stimulus has to be, before a system reacts to it
Growth - irreversible increase in size
Reproduction - producing offspring either sexually or asexually
Excretion - getting rid of the waste products of metabolism
Homeostasis - maintaining a constant internal environment
Nutrition - obtaining food to provide energy and the materials needed for growth
Examples of UNICELLULAR cells:
Paramecium Chlamydomonas
● reproduces asexually by mitosis ● nucleus can divide via mitosis or fuse
● food vacuoles digest food and products through sexual reproduction
expelled to cytoplasm for energy ● metabolic reactions are enzyme-regulated
● contractile vacuoles maintain H2O levels ● cell wall and cell membrane is permeable to
● metabolic reactions are enzyme-regulated allow gas/substance exchange
● cilia is for movement and response to stimuli ● contractile vacuoles maintain H2O levels
● cell membrane controls concentration of ● Chloroplasts is used for photosynthesis
substances ● light sensitive eyespot detects light stimuli
● excretion through diffusion
,Limitations to Cell Size:
● cell size is controlled by surface area:volume ratio.
● The ratio needs to be high for efficient exchange of materials = large surface area but small volume
Small ratio:
1. there will be a slow and inefficient exchange in substances
2. more nutrients will be absorbed/diffused than products excreted
3. build up of waste products causes cell to heat up too fast
4. overheating of cell
Multi-cellular organisms:
● cells work in co-operative groups
● cells work together to give rise to emergent properties: interaction of parts of a complex structure/cell
Cell Differentiation
● specialised tissue can develop through cell differentiation
● Tissue: group of same cells carry out the same specific function
Process:
1. cell differentiation involves the expression of some genes but not others
2. this defines a specific function as different sequences of genes are expressed creating a specialised
tissue
, Stem cells:
● totipotent, pluripotent, multipotent, or unipotent
● found in bone marrow skin and liver
● therapeutic use: replacing damaged skin tissue
● non-therapeutic use: formation of striated muscle
Embryonic Cord Blood Adult
● Totipotent ● Unipotent (only differentiate ● Pluripotent
● genetically different from into blood cells) ● difficult to obtain as it is
adult patient ● easily obtained and stored deep in tissue
● kills embryo (unethical) ● umbilical cord is discarded ● does not kill anything
regardless (ethical) (ethical)
Case Study of Diseases that are treated using Stem Cells:
Stargardt's Disease Leukaemia
● genetic disease ● cancer so not genetic disease
● Malfunctioning of membrane for active ● white blood cells reproduce at an
transport in the retina cells causing vision to uncontrollable rate
decay
Treatment:
Treatment:
1. chemotherapy kills dividing cells
● stems cells are injected in the eye and attach 2. adult stem cells are extracted from bone
to damaged cells which improves vision marrow
3. chemo kills all cells in bone marrow
4. stem cells are returned to patient's body and
replicate at a normal rate
Ethics of Therapeutic Cloning using Stem Cells:
For Against
● stem cell research can pave the way for ● involves the creation and destruction of
new discoveries human embryos
● can be used to cure serious diseases ● embryonic stem cells may develop into
● transplants are less likely to be rejected cancerous cells and cause tumours
using cells that are genetically identical to ● more embryos are produced than needed so
parent the excess are killed
● cells are taken when the embryo has no
nervous system so feels no pain
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