cellular organisation and specialisation Flashcards
What is a tissue?
a group of cells that work together to perform a specific function/ set of functions
What is an organ?
collection of tissues working together to perform a function/ related functions
What is an organ system?
a number of organs working together to carry out an overall life function
Why do multicellular organisms need specialised cells and not single-celled organisms like amoeba?
single-celled organisms have a large surface area to volume ratio, meaning that oxygen can diffuse across their plasma membrane and waste products can diffuse out via the same membrane
BUT
multicellular organisms has a small surface area to volume ration so most of the cells are not in direct contact with the external environment- thus they need specialised cells that are differentiated to carry out a specific function
What is differentiation and how does it work?
When undifferentiated cells become specialised to carry out a particular function depending on which genes are switched on and off (after mitosis)
What is able to happen with the genome in unspecialised cells?
all the cells in its genome are able to be expressed
What does stem cell potency mean?
the ability of a stem cell to become differentiated into any type of cell
What does totipotent mean?
stem cells that can differentiate into any type of cell- not only body cells but also extra embryonic tissues like amnion and umbilicus
What does pluripotent mean?
stem cells that can form all tissue types, only WITHIN an organism, but not whole organisms
What does multipotent mean?
stem cells that can form a range of cells within a certain type of tissue
e.g. haematopoietic stem cells in bone marrow can differentiate into various types of blood cells
What are some sources of stem cells?
-embryonic stem cells
-stem cells in umbilical-cord blood
-adult stem cells (found in developed tissues)- act like a repair system - a renewing source of undifferentiated cells
-induced pluripotent stem cells (iPS cells) - developed in labs by reprogramming differentiated cells to switch on certain key genes and become undifferentiated
-placenta
What is the source of stem cells in plants?
meristematic tissue (meristems)
Where are meristems found?
roots, shoots and in vascular bundles in plants
Why do blood cells need to be replaced so often?
Lifespan of:
erythrocytes: 120 days
neutrophils: 6 hours
