Cell Structure Flashcards
Suggest why eukaryotic cells evolved from prokaryotic cells.
- adaptation of circular DNA into enclosed DNA in a nucleus.
- adaptation of organelles without membranes to organelles with membranes.
- the inability of the cell to create it’s own mitochondria/chloroplasts.
- the mitochondria/chloroplasts having their own DNA and ribosomes.
Give the overall function of:
- the nucleus
- the mitochondria
Nucleus;
- control centre of the cell through the production of mRNA and tRNA, hence protein synthesis.
- retains cells genetic material in form of DNA and chromosomes.
- manufactures ribosomal RNA and ribosomes.
Mitochondria;
- site of aerobic respiration, therefore responsible for production of ATP from respiratory substances.
Give the overall function of:
- the golgi apparatus
- the chloroplasts
Golgi Apparatus;
- modify proteins using carbohydrates to form glycoproteins.
- produce secretory enzymes, and lysosomes.
- secrete carbohydrates.
- transport, modify and store lipids.
Chloroplasts;
- site of photosynthesis.
- manufactured some proteins required for photosynthesis.
Give the overall function of:
- lysosomes
- ribosomes
Lysosomes;
- hydrolysed material ingested by phagocytic cells.
- release enzymes outside cells to destroy surrounding materials.
- digest worn out organelles so useful chemicals can be re-used.
- completely break down dead cells.
Ribosomes;
- site of protein synthesis in cells (translation).
Give the overall function of:
- smooth endoplasmic reticulum
- rough endoplasmic reticulum
Smooth Endoplasmic Reticulum;
- synthesises, stores and transports lipids and carbohydrates.
Rough Endoplasmic Reticulum;
- provides large surface area for protein and glycoproteins synthesis.
- provides pathway for the transport of material throughout the cell.
Explain the different types of electron microscope.
Transmission electron microscope;
- an electron gun shoots a beam of electrons that penetrates the specimen from below, being focused on the specimen by a condenser electromagnet.
- the parts of the specimen that absorb electrons appear dark, others appear light.
Scanning electron microscope;
- a beam of electrons directed onto specimen from above, being passed back and forth in a regular pattern.
-the pattern of the scattering depends on the contours of the specimens surface.
Give the limitations of the two types of electron microscope.
TEM -
- whole system must be in vacuum, so no living specimen.
- specimen must be extremely thin, so electrons can pass through.
- complex staining process required, however only black and white image produced.
- image may contain artefacts from preparation.
SEM -
- whole system must be in vacuum, so no living specimen.
- lower resolving power than TEM.
- complex staining process required, however only black and white image produced.
- image may contain artefacts from preparation.
What is Cell Fractionation?
Describe the two stages in Cell Fractionation.
- The process where cells are broken up and the different organelles they contain separated.
1 - Homogenation;
- cells are mixed with a cold, isotonic, buffer solution and broken up in a homogeniser, releasing the organelles from the cells, then filtered to remove any whole cells or debris.
2 - Ultracentrifugation;
- filtrate placed in a centrifuge and spun at slow speed. heaviest organelles separated to bottom. supernatant removed. process repeats at higher and higher speeds until all organelles separated.
Describe what happens at each of the 5 (1+ 4) stages of mitosis.
Interphase;
- DNA/genetic info replicates.
Prophase;
- chromosomes condense and become visible, the nucleolus disappears and the nuclear envelops disintegrates.
- spindle fibres begin forming.
Metaphase;
- chromosomes line up on equator of cell. spindle fibres begin attaching to chromatids.
Anaphase;
- the spindle fibres attached to chromatids retract to respective poles of the cell, taking chromatids with them.
Telophase;
- spindle fibres disintegrate as chromosomes reach poles and become indistinct.
- nuclear envelope and nucleolus reforms.
What is the importance for mitosis?
Growth;
- when two haploid cells fuse together into a diploid cell they contain all the genetic information required to form the new organism. if the new organism is to resemble it’s parents, all the cells grown from the original cell must be genetically identical.
Repair;
- if cells are damaged or die, it is important that the new cells formed have identical structure and function to the ones that have been lost.
Reproduction;
- single celled organisms divide divide by mitosis to give two new organisms. each new organism is genetically identical to the parent organism.
Describe the 4 stages of binary fission.
1 - circular DNA molecule replicates, and both copies attach to the cell membrane.
2 - the plasmids also replicate.
3 - the cell membrane begins to grow between the two DNA molecules and begins to ‘pinch’ inwards, dividing the cytoplasm into two.
4 - a new cell wall forms between the two molecules of DNA, dividing the original cell into two new daughter cells, each with a single copy of the circular DNA and a variable number of copies of the plasmids.
Describe the 4 stages of Viral replication.
1 - The virus attaches onto a host cell (T Helper cell) using attachment proteins.
2 - The virus injects nuclei acid contains genetic information into the host cell.
3 - The genetic information provides instructions for the host cells metabolic processes to produce viral components.
4 - the viral components are produced and formed into new viruses, which leave the host cell.
What are the two types of cancer?
(Name and describe briefly)
Benign - slow growing tumours, that are more compact and less likely to be life threatening.
Malignant - rapidly growing tumours, that are less compact and more likely to be life-threatening as they can produce tumours in other cells, and travel in the bloodstream.
What is a common treatment for cancer?
Chemotherapy;
- disrupts the cell cycle, however affects all dividing cells.
- prevents DNA replication.
- Interferes with spindle formation in metaphase.
What are the steps in a drug trial?
Pre-clinical;
- Test on isolated molecule
- Test on cell/tissue culture
- Test on small mammal (mouse)
Clinical;
- Test on healthy volunteers (for side effects)
- Test on patients (for optimum doseage)
- Test on large group (>1000) (double-blind trial)
