Cell Division and Specialisation Flashcards
what functions are needed for any organism to stay alive
support/structure
exchange (with environment)
digestion
respiration
reproduction
cell
basic building block
tissue
group of cells with similar structure and similar function
organ
group of tissues working together with a specific function
organ system
group of organs working together with a specific function
organism
group of organ systems that perform all functions necessary to stay alive
egs of cell -> tissue -> organ -> organ system
specialised
having different adaptations to help carry out specific function
nerve cell
what are muscle cells? (skeletal and smooth)
striated muscle cells diagram, what are their 3 adaptations?
sperm cells
root hair cells
absorb water and mineral ions from soil
underground so no chloroplast
photosynthetic cells
= palisade cell, long and thin so lots can fit into top layer of leaf
xylem cells
xylem is a transport tissue in plants that carries water and mineral ions from roots to highest leaves (made up of xylem cells)
UNIDIRECTIONAL TRAVEL
cells are dead?
phloem cells
mitosis (membrane?)
DNA in chromosomes copies itself ready for mitosis. most time is spent in this phase (interphase)
The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus disappears (prophase)
Chromosomes and their copies line up in the middle of the cell (metaphase)
Chromosomes and their copies are pulled to different ends of the cell - ONE SET TO E4ACH SIDE (anaphase)
New membranes form around the chromosomes at each end of the cell (telophase)
The cell membrane pinches in and eventually divides into two daughter cells (cytokinesis)
cell cycle
interphase (DNA replication and growth) - cell gets ready to divide, cell grows, DNA duplicates, more organelles made
mitosis - genetic material separates, SET OF CHROMOSOMES GET PULLED TO EACH SIDE and cell gets ready to divide into 2 daughter cells
cytokinesis (cell division) - cytoplasm and cell membrane split, (2 new daughter cells are made)
cells divide for:
growth (hair, nails)
development (embryos, muscles)
replacement (skin, blood cells)
normal cell division
regulated by genes - ensure cells only divide when needed, then stop
apoptosis: body can destroy cells that are old/damaged (controlled cell death)
tumour
(caused by mutation) cells growing abnormally and uncontrolled
benign vs malignant tumours
metastases
secondary tumours
causes of cancer
lifestyle:
smoking
obesity (bowel)
viruses:
HPY (cervical)
genetics:
faulty BRCA gene (high risk of breast cancer)
carcinogens:
asbestos (lung)
alcohol (liver)
UV exposure (skin)
stem cell
undifferentiated cell that has the potential to become any type of cell needed
what happens during first few days after fertilisation
stem cells divide
differentiation (and eg)
cells developing structural differences enabling them to carry out a specific function
eg cytoplasm and cell membrane elongate making connections over large distances, forming a nerve cell
differentiation in animals vs plants
plant can keep differentiating throughout their life
differentiation is reversible in plants
how can stem cells differentiate into any cell
they have access to all genes
adult / somatic stem cells? why are they needed?
tissue-specific / multi potent stem cells
- they can only differentiate into one type of tissue (with limited types of cells)
- hard to find!
eg bone marrow
because not all cells can undergo mitosis (eg RBCs, skin cells)
bone marrow
soft inner tissue of bones where blood cells are formed
rapidly divide and differentiate to form a variety of cells
can only create blood cells (RBCs, WBCs, platelets)
plant differentiation
- differentiate throughout their life
- undifferentiated cells form at meristems (roots and shoots) where mitosis is almost continuous
- cell don’t differentiate until they are at their final position in the plant
- not permanent- cells can revert back, relocate and respecialise
therapeutic cloning
a way of producing stem cells with the same genetic makeup as the patient
why are embryonic stem cells useful (egs)
dysfunctional/damaged cells that can’t repair themselves cause health problems:
- pancreatic cells -> type 1 diabetes
- spinal cord neurones -> paralysis
- cardiac muscle fibres after heart attack
- brain neurones -> Alzheimer’s disease
why is therapeutic cloning useful (what are the alternatives)
although stem cells can be taken from early developing embryos and stimulated to grow into specific body cells
there is a risk of rejection if coming from a donated embryo - lifelong need for immunosuppressants
there would be fewer problems if it came from a family member or from donor with closely matched tissue types
phloem vs xylem
phloem carries bidirectional the products from photosynthesis
xylem carries unidirectional water and mineral ions
xylem cells are lignified, phloem not but have companion cells
issue with stem cells (dont need to know all)
Clinical issues
* no guarantee of how successful these therapies will be, eg use of stem cells in healing damage caused by Parkinson’s disease
* difficult to find suitable stem cell donors
* difficult to obtain and store a patient’s embryonic stem cells
* mutations have been observed in stem cells cultured for a number of generations - some mutated stem cells have been observed to behave like cancer cells.
* cultured stem cells could be contaminated with viruses which would be transferred to a patient
Ethical issues
* a source of embryonic stem cell is unused embryos produced by in vitro fertilisation
* for therapeutic cloning, is it right to create embryos for therapy, and destroy them in the process?
* embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person.
* at what stage of its development should an embryo be regarded as, and treated as, a person?
Social issues
* educating the public about what stem cells can, and can’t do, is important
* do the benefits of stem cell research and use outweigh the objections?
* much of the research is being carried out by commercial clinics, so reported successes are not subject to peer review
* patients could be exploited - paying for expensive treatments and being given false hope of a cure when stem cell therapies are only in their developmental stages
prokaryotic vs eukaryotic cells
size, outer layers, contents, genetic material, cell division
ribosomes
do protein synthesis
chromosome
