1.1 Introduction to cells Flashcards
What does the cell theory state?
- Cells are the fundamental building blocks of all living organisms
- The smallest organisms are unicellular - they consist of just one cell
- Larger organisms are multicellular - they are composed of many cells
What are the 4 common features of cells?
- Each living cell is surrounded by a membrane, which separate the cell contents from everthing else outside
- Cells contain genetic material which sotres all of the instruction needed for the cell’s activity
- Many of these actvities are chemical reactions, catalysed by enzymes produced inside the cell
- Cells have their own energy release system that powers all of the cell’s activities
What are the 3 core ideas of the cell theory?
1) cells are the smallest unit capable of independent life, organelles cannot survive alone
2) living things are composed of cells. Cells are the fundamental building blocks of all living organisms (unicellular and multicellular)
3) cells only arise from pre-existing cells by the process of cell division (mitosis and meiosis and binary fission)
Why is the cell theory a theory?
Because it is widely excepted but not 100% sure
How could you test the cell theory?
By looking at different organisms
What three types of cells/tissues challenges the cell theory? And how?
- Striated muscle fibers
- Aseptic fungal hyphae
- Giant algae
How does striated muscle fibres challenge the cell theory?
- a muscle cell
- they merged to form long muscle fibers with multiple nuclei.
- They challenge the idea of cells always functioning as a autonomous (independent) unit
How does Aseptic fungal hyphae challenge the cell theory?
- Aseptate differs from a septate hypha because it does not have septas (cross-walls), meaning they have a continuous cytoplasm with multiple nuclei.
- This challenge is the idea that the cell is a single unit.
How does the giant algae challenge the cell theory?
- Giant algae is a unicellular organism.
- Most algae are microscopic and unicellular but the giant algae can grow to 100 mm in width yes still a single cell.
- This challenge is the idea that larger organisms are always made up of many multiple cells.
What is the mnemonic for the 7 functions of life?
MR H GREN
What are the 7 basic functions of life?
All living things carry out these functions:
M - Metabolism
R - Response
H - Homeostasis
G - Growth
R - Reproduction
E - Excretion
N - Nutrition
What is metabolism as a function of life?
Chemical reactions inside the cell, including cell respiration to release energy
What is response as a function of life?
The ability to react to changes in the environment
What is homeostasis as a function of life?
Keeping conditions inside the organism within tolerable limits (water and pH etc)
What is growth as a function of life?
An inversible increase in size
What is reproduction as a function of life?
Producing offspring either secually or asexually
What is excretion as a function of life?
Getting rid of the waste products of metabolism
What is nutrition as a function of life?
Obtaining food, to provide energy and the materials needed for growth
What is the difference between egestion and excretion
Excretion is in the blood and its the procces of getting rid of waste product from metabolic reactions
Egestion is everything you ate thats not absorbed. It is basically the passing of undigested food (faeces)
Compare the nutrition function of paramecium and Chlamydomonas
Paramecium feeds on smaller organism by ingesting and digesting them in vesicles (endocytosis)
Chlamydomonas produces its own food by photosynthesis using a chloroplast that occupies much of the cell
Compare the growth of Paramecium and Chlamydomonas
Paramecium increases in size and dry mass by accumulating organic matter and minerals from its food.
Chlamydomonas increases in size and dry mass due to photosynthesis and absorption of minerals
Compare the response of Paramecium and Chlamydomonas
Paramecium reacts to stimuli, e.g. reverses its direction of movement when it touch as a solid object
Chlamydomonas react to stimuli, e.g. senses where the brightest light is with its eyespot and swim towards it
Compare excretion of Paramecium and Chlamydomonas
Paramecium expels waste products of metabolism, e.g. CO2 from respiration diffuses out of the cell
Chlamydomonas expels waste products of metabolism, e.g. oxygen for photosynthesis diffuses out of the cell
What functions do paramecium and Chlamydomonas have in common?
Metabolism, homeostasis and reproduction
MHR
How is the metabolism function of paramecium and Chlamydomonas the same?
Both produces enzymes which catalyze many different chemical reactions in the cytoplasm
How is the homeostasis function of paramecium and Chlamydomonas the same?
Both keeps internal conditions within limits, e.g. expels excess water using contractile vacuoles
How is the reproduction function of paramecium and chlamydomonas the same?
Both reproduces asexually using mitosis or sexually using meiosis and gametes
What does the rate at which substances cross the plasma membrane depend on?
The rate at which substances cross the plasma membrane of this cell depends on the surface area
What is proportional to the volume of a cell?
The rate of reactions (the metabolic rate of the cell)
For metabolism to continue, what must substances used and waste products in reactions do?
- Substances used in the reaction must be absorbed by the cell
- Waste products must be removed
Why cant cells continue to grow larger and larger to become giant cells?
The metabolic rate of a cell is proportional to its volume – larger cells need more energy to sustain essential functions. For metabolism to continue, substances must be exchanged with the environment. The rate at which substances cross the plasma membrane depends on the SA:V ratio
If the cell grows too large, it will have trouble moving enough nutrients and wastes across the cell membrane.
How do substances move in and out of a cell?
Through the plasma membrane at the surface of the cell
What happens when the surface area to volume ratio is too small?
- Substances will not enter the cell as quickly as they are required
- Waste products will accumulate because they are produced more rapidly than they can be excreted
In terms of heat, how does having a small surface area to volume ration affect it?
Cells may overheat, because the metabolism produces heat faster than it is lost over the cell’s surface
How does the cytoplasm being very close to the environment benefit unicellular organisms?
And unicellular organisms all the cytoplasm is very close to the environment in which they live so diffusion will supply enough oxygen and nutrients to keep the cell alive and active as the diffusion pathway are short
Why is diffusion too slow to enable a sufficient supply to the innermost cells in multicellular organisms?
Because multicellular organisms may have several layers of cells so oxygen and nutrients diffusing in from the outside have a longer diffusion pathway
Why is surface area to volume ratio important in cells?
As the cell grows and increase in size, the surface area to volume ratio decreases, causing a decrease in efficiency of exchange
If the ratio is too small then 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 do growing cells tend to divide and remain small?
To maintain a high surface area to volume ratio suitable for survival or else the cell will eventually die
What are 2 examples of increased surface area within the human body and the purpose of their increased surface area
Vili and microvili in the small intestine help absorb nutrients.
The biconcave shape of red blood cells help carry more oxygen
State two examples were having a large surface area to volume ratio is a disadvantage
Cactus – Plants that live in dry conditions I need to conserve water
Shrew – small mammals that need to conserve body heat or else they would need to eat a lot to conserve body heat
What is an emergent properties and when does it arise?
Propoerties that emerge from the interaction of their celluluar components
What are two examples of emergent properties in multicellular organisms?
- Cells working together to form tissues
- Tissues working together to form organs
what is the difference between reductionism, vitalism, and holism
Reductionism is studying each part of the system separately
Holism is looking things as a whole
Vitalism is believing the nature of life as resulting from a vital force
What is the importance of emergent properties?
Emergent properties help living organisms better adapt to their environments and increase their chances of survival.
How can specialized tissues be developed in multicellular organims?
By cell differentiation
What is division of labour in muticellular organisms?
Different cells perform different functions
How does a cell becoming more specialised help?
They can carry out their role more efficienrly than if they had many different roles
What is differentiation?
The development of cells in different ways to carry out specific functions
* it is a process where some genes will be switched on (expressed) and others will be switched off.
What do all different cell types in a mutlicellular organism all have?
The same set of genes
Compared to unicellular organisms, why do multicellular organisms need specialist cell?
Unicellular organisms have a large surface area to volume ratio meaning it has a fast rate of diffusion of oxygen and waste products.
However multicellular have a smaller surface area to volume ratio move cells or not in direct contact with the external environment so rate of diffusion is low. That’s why multicellular organisms need specialized cell to carry out particular functions to speed things up
What is the name of the process whereby cells become specialized? What type of cell undergoes it?
- Differentiation
- It is a permanent process by which stem cells become specialized into different types of cells
What is a stem cell?
It is a unspecialized cells able to express all of its gene and divide by mitosis
What does it mean when a stem cell is specialised?
When it is specialized they change to perform only a particular function
What makes stem cell suitable for therapeutic uses?
The capacity of stem cells to divide and differentiate along different pathways
What is necessary in embryonic development?
The capacity of stem cells to divide and differentiate along different pathways
What are the 2 key properties of stem cells that makes them one of the most active areas of research in biology and medicine today?
- They** can divide again and again** to produce copious quantities of new cells. They are therefore useful for the growth of tissues or the replacemet of cells that have been lost or damaged
- They are not fully differentiated. They can differentiate in different ways, to produce different cell types
What is meant by therapeutic uses?
They provide therapies for diseases or other health problems
What is a non-therapeutic use of stem cells?
Producing large quantities of striated muscle fibres, or meat, for human consumption
* reduce the need to rear and slaughter cattle
Where can stem cells be found in a human body?
Liver, bone marrow, skin
Which stem cells are the most versatile?
Early stage embryonic stem cells
What changes during the differentiation of stem cells?
- The proportion of the different organelles differs from those of other cells
- The shape of the cell changes
- Some of the contact of the cell changes
How is DNA packaged in a eukaryotic cell?
- DNA is packaged with proteins (histones) to form chromatin.
- DNA is organized around histone proteins in it’s super coiled form to save space and protect the DNA.
What type of genes are usually packaged in the expanded form of DNA? What is the expended form called?
Active genes are usually packaged in an expanded form called euchromatin that is accessible to transcriptional machinery
How are inactive genes packaged?
An inactive genes are typically packaged in a more condensed form called heterochromatin (Saves space, not transcribe)
How can a cell become more specialized?
By expressing fewer genes (More DNA packaged in heterochromatin form instead of euchromatin form)
Describe the different regions of DNA in differentiated cells
Differentiated cells will have different regions of DNA packaged as euchromatin and heterochromatin according to their specific function
What do cell differentiation do besides specializing cells?
They also replaced dead or damaged cells throughout your life with the help of self renewal.
What is self renewal of stem cells?
Self renewal maintains the stem cell pool. Which is when stem cells divide by mitosis to maintain the stem cell pool by having one of the two stem cells to divide again while the other one is differentiated.
What is stem cell’s potency? What are the different potencies?
Stem cell’s ability to differentiate into different cell types. The greater the number of cell types it can differentiate into, the greater its potency.
Totipotent, pluripotent, multipotent, unipotent
What can totipotent stem cells differentiate into? Where can it be found?
Totipotent stem cells can differentiate into any type of cell (capable of expressing all of their genes) including extra embryonic tissues like the placenta, amniotic sac and umbilical cord.
Can be found in zygote and approximately eight or 16 cells after the first divisions
What can pluripotent stem cells differentiate into? Where can it be found?
Pluripotent stem cells can differentiate into all tissue types in an organism but not extra embryonic tissue
That can be found in early embryos (blastocyst)
What can multipotent stem cells differentiate into? Where can it be found?
Multi potent stem cells can differentiate into a range of cells within a certain type of tissue but not all cell types
It can be found in bone marrow
What can unipotent stem cells differentiate into? Where can it be found?
Unipotent stem cells can only differentiate into one type of specialized cell
It can be found in testes which can only differentiate into sperm cells
Where can stem cells be sourced in animals?
Umbilical cord, adult tissues (e.g. bone marow), embryos
What is a blastocyst? Where can embryonic stem cells be found?
Blastocyst is a very early stage embryo. It is a ball of about 50 to 100 cells and it is not yet implanted in the uterus. It is made up of an outer layer of cells, of fluid – filled space and a group of cells called the inner cell mass.
Embryonic stem cells are found in the inner cell mass of the blastocyst.
Where can stem cells be harvested from newborn babies?
From the umbilical cord is an umbilical cord blood
Why can adult tissue stem cells be found in bone marrow, liver and skin? What types of cell can adult tissues stem cells make?
Because those are tissues that need to regenerate/repair frequently. Adult tissue stem cells can only make the type of cells found in the tissue they belong in. For example, blood stem cells (hematopoietic stem) cells can only make the different kinds of cells found in the blood.
What are induced pluripotent stem (iPSCs)
Stem cells that are developed in laboratories by genetically reprogram and differentiated cells to switch on certain key genes and become undifferentiated so they behave like embryonic stem cells again
Where are stem cells present in plants?
Found in meristematic tissue which are the tips of roots and shoots
Also in cambium tissue where the tissue found between xylem + of phloem vessels.
How does the pluripotent nature of animal stem cells and plant stem cells compare?
Plant stem cells remain pluripotent throughout the life of the plant wheres animals stem cells are only multipotent an adults.
What are 3 sources in which stem cells can be obtained?
- Embryos can be deliberately created by fertilizing egg cells with sperm and allowing thre resulting zygote to develop for a few days until it has bwtween four and sixteen cells. All of the cells are embryonic stem cells
- Blood can be extracted from the umbilical cord of a new-born baby and the stem cells obtained from it. The cells can be frozen and stored for possible use later in the baby’s life
- Stem cells can be obtained from some adult tissues such as bone marrow
Why is the use of embryonic stem cells controversial?
Current techniques usually involve the death of the embryo when the stem cells are taken.
* The main question is whether an early stage embryo is as much a human individual as a new-born baby, in which case killing the embryo is undoubtedly unethical
Compare the ease and ethics of extraction between embryonic, umbilical cord blood, and adult tissue
Embryonic can be obtained from excess embryos generated by IVF programs but can only be obtained by destruction of an embryo
Umbilical cord blood stem cells are easily obtained and stored. Though limited quantities available. The umbilical cord is removed at birth and started whether or not stem cells are harvested.
Adult tissues stencils are difficult to obtain as there are very few and are buried deep in tissues. Adult patient can give permission for cells to be extracted.
IVF programes may exploit vulnerable groups (College women getting paid)
Compare the growth potential, compatibility, and differentiation of embryonic, umbilical cord blood, and adult tissue stem cells
Embryonic stem cells are pluripotent – almost unlimited, meaning they can differentiate into any cell type. However they are not genetically identical to the patient.
Umbilical cord blood of stem cells are multipotent - reduced potential (compared to embryonic cells). They have limited capacity to differentiate (what about inducement only naturally divide into blood cells). But they are fully compatible with the patient has a stem cells are genetically identical. No risk of rejection.
Compare the growth potential, compatibility, and differentiation of embryonic, umbilical cord blood, and adult tissue stem cells
Embryonic stem cells are pluripotent – almost unlimited, meaning they can differentiate into any cell type. However they are not genetically identical to the patient.
Umbilical cord blood of stem cells are multipotent - reduced potential (compared to embryonic cells). They have limited capacity to differentiate (what about inducement only naturally divide into blood cells). But they are fully compatible with the patient has a stem cells are genetically identical. No risk of rejection.
Adult tissue stem cells are multi potent – reduced potential and have limited capacity to differentiate (dependent on source tissue). But they are fully compatible with the patient as the stem cells are genetically identical. No risk of rejection.
Compare the tumor risk and genetic damage of embryonic, umbilical cord blood, and adult tissue stem cells
Embryonic stem cells have a higher risk of tumor development. It has a less chance of genetic damage than adult cells.
Umbilical cord blood has a lower risk of tumor development. Also has less chance of genetic damage than adult cells.
Adult tissue stem cells have a lower risk of tumor development but due to accumulation of mutations through the life of the adult, genetic damage is more likely
What is the difference between therapeutic and non-therapeutic uses of some cells?
Therapeutic uses of stem cells provide therapies for diseases or health problems
Non-therapeutic uses of stem cells include producing large quantities of stride muscle fibers (meat) for human consumption
What is Stargardt’s disease?
Stargardt’s disease affects around one and 10,000 children. It is a recessive genetic (inherited) condition. The gene mutation causes an active transport protein on photo receptor cells to malfunction. The photo receptor cells (rods and cones in the retina) degenerate. Causes progressive, and eventually total, lots of central vision
How can stargardt’s disease be treated?
Embryonic stem cells are are treated to divide and differentiate to become retinal cells. The retinal cells are injected into the retina and attach to the retina and become functional. Central vision will improve as a result of more functional retina cells.
This treatment is still at the stage of limited clinical trials, but will likely be used in the future
What is the risk of using embryonic stem cells to treat Stargardt’s disease?
Because embryonic stem cells are not genetically identical to the patient they can be rejected and become tumorous
What is Leukemia?
Leukemia is the cancer of the blood or bone marrow, resulting an abnormally high levels of poorly functioning white blood cells.
What is the treatment of Leukemia? What is the benefit of using hematopoietic stem cells?
- A large needle is inserted into a** bone marrow, usually the pelvis, the fluid is removed** from the bone marrow.
- Hematopoietic stem cells (HSCs) or extracted from this fluid and are stored by freezing them. They are multi potent adult stem cells and so only have the potential for producing blood cells.
- A high dose of chemotherapy drugs is given to the patient, to kill all the cancer cells in the bone marrow which loses its ability to produce blood cells.
- The HSCs are transplant back into the patient’s body which reestablishes themselves in the bone marrow, divide and differentiates into new red and white blood cells.
The use of a patient’s own HSCs means there is far less risk of immune rejection then with traditional bone marrow transplant.
Where can stem cells be found in a human body?
Liver, bone marrow, skin
