Stem cells and differeniation Flashcards
Enthrocytes
Flattened biconcave shape - increases SA:V ratio, maximising the oxygen absorption - quicK diffusion rate
No nuclei - more space for haemoglobin
Flexible - to fit through narrow capillaries
Neutrophils
Part of immune response
Multi lobed nucleus- for squeezing through small gaps to get to site of infection
Granular cytoplasm - Contains lysosomes that conrain enzymes used to attack pathogens
Sperm cell
Male gamete
Tail/ flagellum - capable of movement
Lots of mitachondria/ enzymes - supply energy to swim
Acrosome on head- digestive enzymes are released to digest protective layers around the ovum and allow spleen to penetrate - fertilisation
palisade
Found in mesophyll
- chloroplasts ABSORB large amounts for photosytnethsis
- cells CLOSELY slacked to form a continuous layer
THIN walls increase diffusion rate of CO2
Large vacuole to maintain turgor pressure
Chloroplasts move within cytoplasm in order to absorb more light
Root hair cells
Surfaces of roots near growing tips
- long hair liek extensions called Root hair cells which I crease the surface area of cell
This MAXIMISES uptake
Lots of mitachondria which provide more energy for active transport
GUARD cells
Form small opening called stomata
Needed for co2 to enter plants for photosynthesis
Loosing h20 causes them to become LESS swollen as a result of osmotic forces - change shape and stoma closes to prevent further loss
Cell wall - thicker on ONE side
Cell doesn’t change shape symmetrically as it’s volume changes
What is a tissue
A tissue is made of a collection of diffferentiated cells that have a specialised function/s
As a result each tissue is adapted for a particular function within the organism
4 main categories of tissues in animals
Nervous tissue
Epithelial tissue
Muscle tissue
Connective tissue
Nervous tissue
Adapted to support the transmission of electrical impulses
Epithelial tissue
Adapted to cover body surfaces, internal and external
Muscle tissue
Adapted to contract
Connective tissue
Adapted to either to hold other tissue together as as a transport system
Squamous epithelium
Made up of specialised squamous epithelial cells, sometimes lnown as a PAVEMENT epithelial due to flat appearance
Very THIN due to squat/ cells that make it up and only one cell thick
Present when rapid diffusion across a surface is essential
Forms lining of lungs and allows RAPID diffusion of oxygen into the blood
Ciliated epithelium
Made up of ciliated epithelial cells
Hair like structure called CILIA on one side - move in RHYMIC manner
Lines tranchea causes mucus to be swept away by the lungs
Goblet cells RELEASE mucus to trap unwanted particles present in the air , preventing particles which may be bacteria from reaching alveoli once inside the lungs
Microtubules - 9+2 arrangement
Fallopian tubes
Mobile or stationary e.g. sensory organs
Muscle
Needs to be able to contact in order to move bones which In turn move the different part of the body
Different types of muscle fibres
Smooth muscle
Inability to control their movement
HOLLOW organ e.g. uterus and stomach
Skeletal muscle
Attach to bones and have the main function of contracting to facilitate movement of our skeleton
Contain microtubules which contain contractile proteins
Cardiac muscle
High contractile strength
SOLELY in the walls of the heart
Similarities to skeletal muscles in that is stimulated and smooth muscles in that is contraction are NOT under contious control
Epidermis
Single layer of closely packed cells covering surfaces of plants
Covered by wa y cuticle( waterproof)to prevent loss of water
Stomata- formed by a pair of guard cells that open and close
Allow CO2, O2 and water vapour in and out
Short distance so light can penetrate - 1 cell thick, transparent
Protective barrier agianstpp
Xylem tissue
Type of vascular tissue responsible for the transport do water and minerals
Tissue is composed of vessel elements which are composed of vessel elements - ELONGATED dead cells
Walls of these cells are strengthened with a waterproof material called lignin, which provides structural supporT
NON living
Pits - allow water to leave xylem to get to shoots
Phloem
Type of vascular tissue
Responsible for transport of organic nutrients particularly sucrose from leaves and stems where it’s made
Composed of volume of sieve tube cels Seperated by perforated walls called sieve plates
Connected to companion cells - ATP for active transport
No nucleus - more space
Both directions
Parenchyma - store food and release chemicals do not eaten by herbivores
Organs
Collection of tissues that are adapted to perform a particular function in an organism
Organ systems
Large multicellular organisms have coordinated organ systems
Each organ system is composed of a number of Organs working together to carry out a major function in the body
What are stem cells
Able to undergo cell division again and again and are the source of new cells necessary for growth development and tissue repair
Once stem cells become specialised they loose the ability to divide entering the g 0 phase if the cell cycle
Activity do stem cells has to be strictly controlled
Stem cell potency
Ability to differentiate
The greater the number of cell types it can differentiate into the greater the potency
Totipotent stem cells
Can differentiate into ANY type of cell
Fertilised egg, zygote and the 6 or 16 cells from its first miotic divisions are TOTPOTENT
Destined to eventually produce a whole organism
They can also differentiate into extra-embryonic tissues liek the Anouium and umbilicus
Differentiate into cells which produce the embryo and placenta
Pluripotent cells
Can form ALL tissue types but not whole organisms
Present in early embryos and are the origin of the different types of tissues within an organism
Multi potent
The stem cell can only form a range of cells within a certain types of tissue
Haemotopeitic cells in bone marrow are multi potent because this gives rise to various types of blood cell
Sources of plant stem cells
Meristems/meristematic tissue
Found where growth occurs in a plant E.g. Tips of roots and shoots
Meristematic tissue can be found between phloem and xylem tissue(vascular cambium) Cells found here will DIFFERENTIATE into cells found in xylem and phloem
this allows vascular tissue to grow as the plant grows, the pluripotent nature of stem cells in meristem occurs throughout WHOLE life of plant
Sources of animal stem cells - embryonic stem cells
An embryo develops from a fertilised egg
All the cells in an embryo start off identical and undifferentiated - they are embryonic stem cells (TOTPOTENT)
When do embryonic stem cells change to pluripotent state
They can become specialised to form any type of cell by switching gens on and off
Whole new organism develops form embyronic stem cells
After 7 days the mass of cells, BLASTOCYST, it’s in its pluripotent state- remain in this state until birth
Adult stem cell - sources of animal stem cells
Some stem cells remain in the body of adults , found in limited numbers at certain locations
Can differentiated into related cell types ONLY
E.g. Bone marrow - can only differentiate into blood cells adn cells of immune system
Multi potent, but evidence they can artificially be triggered to be PLURIPOTENT
Can be harvested from umbilical cord ( blood stem cells )
Where can adult stem cells be found
Brain, eyes, blood,heart, liver, bone marrow, skin, muscle
What is differentiation
The process of a unspecialised cell becoming specialised and having a specific function
Replacement of red blood cells
Erythrocytes are ESSENTIAL for oxygen transport
Due to lack of nucleus and organelles - live for only 120 days
Need replacing constantly
Stem cell colonies in the bond marrow produce 3 billion per kg of body mass per day
Replacement of white blood cells
Neutrophils
Essential role in immune system
Live for around 6 hours and the colonies of bone marrow produce 1.6 billion per kg per HOUR
Figure increases during infection
Ethics - stem cells
Removal of stem cells from embryos - destruction, live begins at contraception - MURDER
Possibly having another child just so they can use the umbilical cord for stem cells
Adult stem cells- don’t divide as well and are likely to get a mutation
Test on rats adn animals- give them treatments developed by stem cells
Uses of stem cells examples?
Heart disease - muscle tissue in heart damaged aw a result of heart attack
Type 1 diabetes - pluripotent stem cells to produce glucose responding cells that RELEASE INSULIN
Parkinson’s
Birth defects
Macular disease
Alzheimer’s
Drug trails
Development biology
Burns
Spinal injuries -stem cells to repair spinal cord- repair nerve ends
Stem cells - Alzheimer’s
Transplanting neurall stem cells into brain of mice = POSITIVE EFFECT
Build up of abnormal proteins
Burns - stem cells
Stem cell grown on biodegradable meshes can produce new skin for burn patients- quicker than Normal process of taking grade from at other part of the body
Development biology - stem cells
With their ability to divide indefinitely, and differentiate
Study of changes that occur as multicellular organisms grow and develop from single cell and why things go wrong
