1.1-1.7 Flashcards
Why are cells the smallest unit of life?
They are surrounded by a membrane and although there are smaller things that live in cells they are not the smallest unit of life because they require cells around them to live
Why do we need cells for energy?
They are the site of all chemical reactions for life
What are exceptions to cell theory?
- striated muscle cell
- aseptate fungal hyphae
- giant alga
Why is striated muscle cell an exception to cell theory?
The size is irregular ( can be up to 30cm long) and each cell has multiple nuclei ( between 2 and 180)
Why is aseptate fungal hyphae an exception to cell theory?
Instead of having cell- like sections, a hypha is an uninterrupted tube like structure with many nuclei spread along it
Why is giant alga an exception to cell theory?
A uni cellular organism which is 10 cm in size
What are the 7 fundamental processes for life in unicellular organisms?
Metabolism Response Homeostatis Growth Reproduction Excretion Nutrition
What is metabolism?
The speed at which reactions take place in an organism
What is homeostasis?
Maintaining a constant internal environment suitable for all processes for survival
What is excretion?
The removal of waste, to avoid poisoning
What is nutrition?
Everything needs to take in some form of food in order to release energy necessary for other body processes
How does paramecium carry out the 7 functions of life?
Metabolism- cytoplasm
Reproduction- divides by mitosis
Homeostatis- has a contractile vacuole, which manages the water content
Growth- consumes and assimilates biomass then gets larger until it divides
Response- cilia
Excretion- plasma membrane controls what leaves the cell
Nutrition- food vacuoles store organisms that paramecium has consumes
How does an increasing surface area in a cell affect the volume: surface area ratio?
As the total surface area increases, the ratio between the surface area: volume decreases
Why is it important for a cell to have a high SA:V ratio?
If the ratio is too small, substances will not diffuse into the cell as quickly as they are required to.
If the rate is too small the waste products are unable to leave the cell and will accumulate, produced more rapidly than they can be excreted
What happens as a result of cells being too big?
They will reproduce and divide by mitosis , as if it gets too hot, waste products cannot be excreted fast enough and diffusion isn’t occurring fast enough
How do unicellular and multicellular organisms maximise SA:V ratio?
Unicellular- cilia( root hair cells, villi)
Multicellular - folding up ( e.g. Alveoli in lungs)
What is leukaemia?
Cancer of blood and bone marrow, abnormal white blood cells that do not function properly. Thought to originate in blood stem cells.
How is leukaemia treated?
Bone marrow transplants containing stem cells ( haemotopoietic stem cell transplant ), differentiate to form healthy white blood cells.
Chemotherapy and radiotherapy destroy white blood cells
What are side effects of leukaemia treatment?
- infections from donor
- graft- versus- host disease ( rejection- cells implanted attack cells from host body)
What is stargardt disease?
Progressive vision loss that can effect children. It is a recessive genetic condition.
What is treatment for statgardt disease?
Growing retinal pigment epithelium cells from stem cells and injects under retina, supports photo receptor with results
What are the steps in therapeutic cloning?
- Nucleus of an ovum removed and replaced with somatic cell of patient
- Cell administered electric shock- starts dividing
- Blastocyst stage- genetically identical tissues for patients
What are the terms of stem cell research?
It is allowed to research stem cells from embryos but they must be destroyed after 14 days to avoid human cloning
What are factors of using embryos for stem cell research?
- obtained from IVF excess embryos
- destructs embryos- ethical issue
- growth potential almost unlimited
- High risk of tumours
- can differentiate any cell type
- less chance of genetic damage
- not genetically identical to patient
What are factors of using umbilical cord blood for stem cell research?
- easy extraction but limited quantities
- ethically ok- umbilical cord is discarded anyway
- reduced growth potential
- lower risk of tumours
- limited capacity for differentiation- blood cells
- less chance of genetic damage
- not genetically identical to patient
What are factors of using adults for stem cell research?
- stem cells difficult to obtain
- adults can give permission
- reduced growth potential
- lower risk of tumours
- limited capacity for differentiation- depends on source tissue
- genetic damage can occur as mutations accumulate throughout life
- fully compatible as genetically identical to patient
What are the benefits of an electron microscope?
Have a much higher resolution than light microscopes
Reveal the ultra structure of cells
What is the formula for the magnification of an electron microscope?
I
_______
A x M
What is resolution?
The shortest distance between 2 points that can be distinguished
Properties of prokaryotes?
- unicellular organisms like bacteria
- no nucleus, DNA located in nuclear area
- smaller than eukaryotic cells
- cell wall
- contain plasmids
- DNA in single loops
- no mitochondria
- 70 ribosomes
- free floating DNA in cytoplasm
What are the stages of binary fission in prokaryotic cells?
- DNA replicated and attaches itself to the plasma membrane
- the cell elongates to separate chromosomes
- membrane invaginates, pulling itself together in the middle
- the cell splits into 2 daughter cells
Properties of eukaryotes
- larger sized cell
- no cell wall, except in plants
- DNA associated with histoine proteins
- no plasmids
- DNA in separate chromosomes
- DNA in membraned nucleus
- has mitochondria
- 80 ribosomes
Similarities between prokaryotes and eukaryotes?
Cell membrane, DNA, ribosomes, metabolism, require energy, cytoplasm
What is an animal extra-cellular matrix?
A secretion, sometimes if glycoproteins. It sits between cells and can perform many additional functions such a support, adhesion, filtering, as well as a basis for the formation of tissue
What happens when phospholipids are out in water?
An emergent property is that phospholipids will self organise to keep their hydrophilic heads wet and hydrophobic tails dry
What is micelle?
A formation where hydrophilic heads face the water and tails join to avoid water
What is a liposome?
Liposomes have a bilateral formation to contain water inside the cell but still keep it away from the membrane
What is a phospholipid bilayer?
This is arranged with the hydrophilic phosphate heads facing outwards and the hydrophobic fatty acid tails ( consisting of hydrocarbon chains) facing into the middle of the bilayers. It is a barrier against all molecules except the smallest, CO2 and O2.
What are integral proteins?
They are usually involved in transporting substances across the membrane and usually span from 1 side of the phospholipid bilayer to the other
What are peripheral proteins?
They sit on surfaces and slide around the membrane quickly and collide with each other, but will never flip from one side to another. The ones on the inside of the membrane are involved in maintaining cells shape or motility. Might also be enzymes.
What are glycoproteins?
Usually involved in cell recognition, which is part of the immune system. Also act as reception a in cell signalling such as with hormones
What is cholesterol?
It binds together lipid in the plasma membrane, reducing its fluidity as conferring its structural stability
What is a fluid mosaic model?
The structure of a membrane in fluid state, on electron micrographs the proteins form a mosaic pattern
How is the structure of phospholipids strong?
- hydrophobic hydrogen tails attracted to each other
- hydrophilic phosphate heads attracted to each other
- heads suited to high water content of tissue fluid and cytoplasm on either side of membrane
- Tails repel water, creating a barrier between the internal and external water environments of the cell + a barrier to movement of charged molecules
- charges in phospholipids attract them, making them stable but allowing some movement
- presence of cholesterol molecules increases stability
What do channel proteins do?
Span membranes, movement of large molecules. There are passive and active membrane pumps- allow specific ions through
What do receptor proteins do?
Detect hormones arriving at cell to signal changes in function involved in other cell and substance recognition.