Tushar 1.1 - Intro to Cells Flashcards
Cell theory states which 3 things
- cells are the smallest unit of life
- all cells come from pre-existing cells
- all organisms are made up of one or more cells (unicellular/multicellular)
Exceptions to the cell theory
Striated muscle = v long and multiple nuclei
Giant algae = unicellular but v big
Aseptate fungi = hypha is uninterrupted and not divided into cells (no cell walls dividing) + many nuclei spread along it
2 examples of unicellular organisms
Paramecium
Chlamydomonas
What are the functions of life
Metabolism Response Homeostasis Growth Reproduction Excretion Nutrition
How does paramecium carry out the functions of life
Metabolism - metabolic reactions occur in cytoplasm
Respiration - by mitochondria
Homeostasis - by contractile vacuole, they can fill up and expel excess water out of the cell
Growth/reproduction - nucleus can divide for reproduction
Excretion - Contractile vacuole
Nutrition - food ingested by endocytosis, have food vacuole containing organisms consumed. these are digested and absorbed into the cytoplasm
How does chlamydomonas carry out the functions of life
Metabolism : reactions occur in cytoplasm by enzymes
Respiration: mitochondria
Homeostasis: contractile vacuoles + eyespot which detects bright light so can move towards light
Growth/nutrition: have chloroplast for photosynthesis, helps make food and grow
Reproduction: asexually and sexually
Excretion: waste products leave by diffusion
Limitation to cell size
If cells are too big, then SA:V will be smaller
So there will be slower absorption of nutrients and excretion of waste
Small SA:V can also lead to overheating of cells
Note that bigger SA:V ratio will not increase the rate of diffusion, it would just mean that more particles can diffuse through at once but at the same rate of diffusion
Higher volume = more heat and waste produced
Emergent properties
are from the interaction of specialised cells in multicellular organisms.
What is differentiation and how does it happen
Specialised tissues are formed by differentiation, this involves the expression of some genes and not others
All cells in the body = same DNA (as come from zygote)
Certain hormones are introduced, this causes some genes to be expressed and some not be be expressed. Depending on which gene is expressed, the cell specialises into a particular cell
Stargardt’s disease
- 2 recessive genes
- blindness
- malfunction of a membrane protein used for active transport in retina cells, causes vitamin A waste product to not be excreted properly and to accumulate, this worsens vision over time
Treatment
embryonic stem cells differentiated into retina cells and these retina cells are then injected into the eye
Leukemia
- Cancer, excessive production of WBCs (wbc are made in bone marrow)
- Have to kill the cancer cells that are producing too many WBCs
- fluid extracted from bone marrow
- stem cells extracted from fluid and stored, these adult stem cells are multipotent, they can only differentiate into blood cells
- chemotherapy given to patient to kill cancer cells in bone marrow, but this also kills healthy cells that produce blood cells
- stem cells inserted into patients body, these go to bone marrow and produce blood cells`
Pluripotent
Multipotent
Totipotent
Pluripotent: can differentiate into any cell (embryonic stem cells)
Multipotent: differentiates into specific cell types only (adult stem cells and cord blood stem cells)
Totipotent cell: a single cell that can give rise to a new organism, given appropriate maternal support
What are stem cells, therapeutic and non-therapeutic uses and their description
Stem cells: unspecialised cells
therapeutic uses: related to healing a disease. e.g. diabetes
non-theraputic uses:e.g. producing meat for consumption, no healing disease
- have capacity to divide
- can be used to produce large culture of identical cells
- used in research
Different types of stem cells
embryonic stem cells - obtained by vitro fertilization
cord blood stem cells - from umbilical cord, take stem cells in blood and store in cold temp so they can be used later in patients life
adult stem cells
Embryonic stem cells
- pluripotent
- risk of becoming tumor
- can be rejected by patients body
- killing of embryo
