Stem Cells and organisation Flashcards
What is a totipotent cell?
- Undifferentiated stem cell which has the potential to become a whole organism.
- They can become any part of the organism including placenta, umbilical cord and amniotic membranes
What is a pluripotent cell?
- stem cells which have started to differentiate but still have the potential to become any of the different types of tissue within the organism
- by differentiating they have lost the ability to form the extra-fetal tissues so can’t become the whole organism
What is a multipotent cell?
-stem cells which have differentiated to the point where they can only form a range of cells within a certain type of tissue
What happens after fertilisation? Describe what occurs at each of the stages A-F
A zygote is formed which begins to divide by mitosis:
A) 2 cell stage - blastomere
B) 4 cell stage - zona pelucida (jelly coat of egg)
C) 8 cell stage
D) Morula - stem cells are totipotent
E) Early blastocyst - differentiation has occurred - inner cell mass stem cells become embryo - outside stem cells become the placenta
F) Late blastocyst - stem cells now pluripotent
What is a cell in the hierarchy of organisation within living things?
- simplest unit of life
- can differentiate and become specialised for a particular function
Describe and explain the specialisation and function of the animal cell ‘erythrocytes’ (red blood cells)
- disc shaped to create high surface area to volume ratio
- all haemoglobin molecules near surface for diffusion of oxygen
- biconcave shape to create large surface area and some flexibility when moving through narrow capillaries
- greater thickness around edge allows for more haemoglobin
- nucleus and other organelles are lost to increase volume available
- packed with haemoglobin which has an affinity for oxygen and carries it to respiring tissues
- all of these adaptations helps the red blood cell to transport oxygen
Describe and explain the specialisation and function of the animal cell ‘neutrophils’
- many lysosomes so ingested particles can be broken down
- lots of ribosomes and RER needed to make proteins
- golgi required for making the lysosomes + packing enzymes into vesicles
- lots of mitochondria so sufficient aerobic respiration can take place to make enough ATP to provide energy for all anabolic processes
- plasma membrane has receptors to detect foreign antigens
- nucleus in lobes so more flexible
- all of these adaptations help the cell to carry out its function of phagocytosis
Describe and explain the specialisation and function of the animal cell ‘spermatozoa’ (sperm cells)
- haploid nucleus
- flagellum made of microtubules for locomotion and motile movement (swim independently)
- many mitochondria to do aerobic respiration to produce enough ATP to supply energy required for swim
- acrosome (specialised lysosome) ruptures allowing for the enzymes to be released and penetrate through egg’s jelly coating
Describe and explain the specialisation and function of the plant cell ‘palisade mesophyll’
- contain many chloroplast which can move along cytoskeleton tracks towards a light source
- chloroplast pushed close to cellulose cell walls by turgor pressure exerted by vacuole
- thin cellulose cell walls so short diffusion distance pathway for co2 for photosynthesis
- tightly packed together and ability to move in palisade mesophyll tissue so there’s a high concentration of chloroplast where light is available
- specialised for photosynthesis
Describe and explain the specialisation and function of the plant cell ‘root hair cell’
- found on outer surface of roots with hair like projections protruding the soil
- shape gently increases surface area of the cell for uptake of water and minerals from soil
- cell wall is fully permeable and contains lots of intrinsic proteins for transport of polar molecules
- some will be actively transported so many mitochondria present so ATP can be made to drive import of polar molecules against concentration gradient
Describe and explain the specialisation and function of the plant cell ‘guard cell’
- two guard cells surround each stoma (mostly found on underside of leaf)
- has exchange takes place through stomata including uptake of co2 from atmosphere for photosynthesis
- when water vapour exits, function of guard cells is to open stomata to allow in co2 when light is available but to avoid water loss when dark
- guard cells contain chloroplast so when light is available it’s absorbed and photosynthesis can occur
- ATP used to actively pump ions into the guard cells to lower water potential so water moves in from surrounding cells
- cellulose cell wall is thinner on outside and thicker on inside edge so when cell becomes turgid the cell distorts its shape because of the unevenness and opens the stomata.
What is a tissue in the hierarchy of organisation within living things ?
-a collection of differentiated cells that are similar and work together to carry out a function
What is a nervous tissue?
Sensory neurones, relay neurones and motor neurones all work together to transmit nervous impulses
Explain why blood is a tissue
-all of the cells (red and white blood cells, platelets) have the same origin
Describe and explain the function/ location of the specialised animal tissue ‘simple squamous’.
Simple squamous:
- epithelial tissue = covers body surfaces
- simple epithelial = one cell thick
- squamous epithelial = flattened in shape to reduce diffusion pathway for gas exchange.
- it forms the walls of the alveoli and capillaries to allow rapid diffusion of oxygen from the air into the blood
