1.1 - Intro To Cells Flashcards
What are the common characteristics that all cells share?
- Cells are surrounded by a membrane
- Cells contain genetic material
- Chemical reactions catalysed by enzymes take place in cells
- Cells have their own energy release system that powers all of the cell’s activities
How do you convert millimetres into micrometers?
Multiply by 1000
How do you convert micrometers into millimetres?
Divide by 1000
Magnification equation :
Magnification = size of image / actual size of specimen
What are striated muscle cells?
The type of tissue that we use to change the position of our body.
Made out of muscle fibres, which are similar to cells - surrounded by a membrane, formed from pre-existing cells, have their own genetic info and energy release system.
How are Striated Muscle Cells atypical cells?
⭐️They are much larger than most animal cells⭐️
- In humans - average length of 30mm
- Other human cells are mostly less that 0.03mm in length
⭐️They have many nuclei⭐️
- Can have up to several hundred
- Human cells only have one
What are hyphae?
Make up fungi
Narrow thread-like structures
Usually white in colour
Have a fluffy appearance
Have a cell membrane and cell wall
Uninterrupted tube like structure with many nuclei
Why are hyphae atypical cells?
They have many nuclei in their long threads
What are algae?
Organisms that feed themselves by photosynthesis, and store their genes inside their nuclei.
But - they are simpler in their structure and organisation than most plants
Why are giant algae atypical?
Can grow to as long as 100mm
But - is unicellular
What are the 7 functions of life that all cells carry out?
Metabolism
Reproduction
Homeostasis
Growth
Response
Excretion
Nutrition
What is the metabolism of a cell?
Large numbers of chemical reactions that take place in the cytoplasm of the cell
The metabolic rate of the cell is proportional to what?
The volume of the cell
What happens if a cells surface area to volume ratio is too small?
Substances will not enter the cell as quickly as they are required - and waste products will accumulate because they are produced more rapidly than they can be excreted
Why surface area to volume ratio is related to heat production and loss?
If the surface area to volume ratio is too small, then cells may overheat because the metabolism produces heat faster than it is lost over the cell’s surface
Define multicellular
Organisms consisting of a single mass of cells, fused together
Define emergent properties
The interaction of the component parts of a complex structure
The whole is greater than the sum of its parts
Define division of labour
In multicellular organisms, different cells perform different functions
Define tissue
A group of cells which specialise in the same way to perform the same function
Function of a red blood cell
To carry oxygen
Function of a rod cell in the retina of the eye
To absorb light and transmit impulses to the brain
Benefits of cell specializing
Cells can carry out their role more efficiently than if they had many different roles
Can develop the ideal structure - with the enzymes needed to carry out all of the chemical reactions associated with the function
Define differentiation
The development of cells in different ways to carry out specific functions
How many distinctively different highly specialised cell types have been recognised in humans?
220
How do specialised cell types develop?
By differentiation
What are the similarities in all 220 cell types in the human body?
They all have the same set of genes - differences in structure and activities
How many genes are in the human genome approximately?
25,000
Define the term ‘expressed’
When a gene is being used in a cell, the gene is switched on - and not others
Why cell differentiation occurs?
Because a different sequence of genes is expressed in different cells
Define zygote
When a sperm fertilises an egg cell
When does an embryo form?
When the zygote divides to give 2 cells - cell continues dividing
Define stem cells
The zygote and the cells of the early embryo which are extremely versatile and capable of differentiating into numerous cell types
2 key properties of stem cells
- Stem cells can divide over and over to produce copious quantities of new cells. Useful for the growth of tissues or the replacement of lost or damage cells
- Stem cells are not fully differentiated - can differentiate in different way to produce different cell types
Define ‘therapeutic’ cell uses
Uses that provide therapies for diseases or other health problems
Potential uses of embryonic stem cells - THERAPEUTIC
- produce regenerated tissue - skin for burn victims
- healing diseases where a particular cell type has been lost or is malfunctioning - Type 1 diabetes
- possibility to grow whole replacement organs
Potential uses of embryonic stem cells - NON-THERAPEUTIC
Using large amounts of striated muscle fibres for human consumption - meat - no need to rear and slaughter cattle
Where stem cells are present in adult humans which enable regeneration and repair
In many human tissues - bone marrow, skin, liver
Where stem cells are in adult humans that allow for limited repair
Brain, kidney, heart
Describe Stargardt’s macular dystrophy
Genetic disease which develops in kids 6-12. Most cases due to a recessive gene mutation, which causes a membrane protein used for active transport in retina cells to malfunction, causing photo receptive cells in the retina to degenerate - degeneration of vision
Define photoreceptors cells
Cells in the retina which detect light
Treatment of Stargardt’s disease
Injecting retinal cells derived from embryonic stem cells into eyes
Describe leukaemia
Type of cancer which involves the production of abnormally large numbers of white blood cells
Where are white blood cells produced?
Bone marrow - soft tissue in the hollow of bones
How to cure Leukaemia (hypothetically)
The cancer cells in the bone marrow that are producing excessive numbers of white blood cells must be destroyed
Treatment of leukaemia
Cancer cells in bone marrow are killed with chemicals - CHEMOTHERAPY
- some white blood cells are needed though to fight disease SO:
Fluid is removed from the bone marrow, stem cells are extracted from the fluid, patient undergoes chemotherapy, cancer cells are killed and bone marrow loses ability to produce blood cells, stem cells are returned to the bone marrow - where they re-establish themselves, multiply, and start to produce red and white blood cells
How stem cells are obtained
Creation of embryos, blood extracted from the umbilical cord of a newborn baby, stem cells from some adult tissues - like bone marrow
STRENGTHS - embryonic stem cells
Almost unlimited growth and potential
Can differentiate into any cell type in the body
Less chance of genetic damage due to the accumulation of mutations, than with adult stem cells
LIMITATIONS - embryonic stem cells
More risk of becoming tumour cells than adult stem cells - excessive division
Likely to be genetically different from an adult patient recovering the tissue
Removal or cells from an embryo kills it - when more than one cell is taken
STRENGTHS - cord blood stem cells
Easily obtained and stored
Commercial collection and storage services already available
Fully compatible with the tissues if the adult that grows from the baby - no rejection probs occur
Umbilical chord is discarded whether or not stem cells are taken from it
LIMITATIONS - cord blood stem cells
Limited capacity to differentiate into different cell types - only naturally develop into blood cells
Limited quantities of stem cells from one baby’s cord
STRENGTHS - adult stem cells
Less chance of malignant tumours developing than from embryonic stem cells
Fully compatible with the adults tissues, so rejection problems do not occur
Removal of stem cells does not kill the adult from which the cells are taken
LIMITATIONS - adult stem cells
Difficult to obtain as there are very few of them, and they are buried deep in tissues
Less growth potential than embryonic stem cells
Limited capacity to differentiate into different cell types
Arguments against stem cell research
Involves the killing of an embryo
Unethical to create human lives solely for the purpose of obtaining stem cells
Arguments for stem cell research
Have the potential to allow methods of treatment for diseases and disabilities that are currently incurable - reduce the suffering of some individuals
