Topic 2A- Cell Structure and Division Part 2 Flashcards
What are the description and functions of the following prokaryotic organelles:
Cytoplasm
Plasma Membrane
Cell Wall
Capsule
Plasmids
DNA
Flagellum
The cytoplasm of a prokaryotic cell has no membrane-bound organelles (unlike a eukaryotic cell). It has ribosomes- but they’re smaller than those in a eukaryotic cell
Just like in a eukaryotic cell the plasma membrane is mainly made of lipids and proteins. It controls the movement of substances into and out of the cell
The cell wall supports the cell and prevents it from changing shape. It’s made of a polymer called murein. Murein is a glycoprotein (a protein with a carbohydrate attached)
Some prokaryotes (eg bacteria) also have a capsule made up of secreted slime. It helps to protect bacteria from attack by cells of the immune system
Plasmids are small loops of DNA that aren’t part of the main circular DNA molecule. Plasmids contain genes for things like antibiotic resistance, and can be passed between prokaryotes. Plasmids are not always present in prokaryotic cells. Some prokaryotic cells have several
Unlike a eukaryotic cell, a prokaryotic cell doesn’t have a nucleus. Instead, the DNA floats free in the cytoplasm. It’s circular DNA, is present as one long coiled-up strand. It’s not attached to any histone proteins
The flagellum (plural flagella) is a long, hair-like structure that rotates to make the prokaryotic cell move. Not all prokaryotes have a flagellum. Some have more than one.
What are and aren’t viruses?
What are viruses (description)?
What is there size in comparison to a bacterial cell?
What don’t viruses have unlike bacteria?
What do all viruses do and what are these other cells called?
What are the three parts to a virus (in detail)?
What process do prokaryotic cells divide by?
What happens in this process?
Describe and explain the four stages of this process?
Viruses are acellular- they’re not cells
Viruses are just nucleic acids surrounded by protein- they’re not even alive
They’re even smaller than bacteria (eg HIV is about 0.1 um across)
Unlike bacteria, viruses have no plasma membrane, no cytoplasm and no ribosomes
All viruses invade and reproduce inside the cells of other organisms. These cells are known as host cells
- Viruses contain a core of genetic material- either DNA or RNA
- The protein coat around the core is called the capsid
- Attachment proteins stick out from the edge of the capsid. These let the virus cling on to a suitable host cell
Binary Fission
The cell replicates (makes copies of) its genetic material, before physically splitting into two daughter cells
- The circular DNA and plasmid(s) replicate. The main DNA loop is only replicated once, but plasmids can be replicated loads of time
- The cell gets bigger and the DNA loops move to opposite “poles” (ends of the cell)
- The cytoplasm begins to divide (and new cell walls begin to form)
- The cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of the plasmid(s).
How do viruses replicate by and describe in full detail?
What do different viruses have and therefore what do they require?
What therefore happens as a result of this?
What don’t viruses do and why?
What do viruses do instead to the host cells (full detail)?
Viruses use host cells to replicate themselves. Viruses use their attachment proteins to bind to complementary receptor proteins on the surface of host cells
Different viruses have different attachment proteins and therefore require different receptor proteins on host cells
Some viruses can only infect one type of cell (others can infect lots of different cells)
Because they’re not alive, viruses don’t undergo cell division
They inject their DNA or RNA into the host cell- this hijacked cell then uses its own “machinery” (eg enzymes, ribosomes) to do the virus’s dirty work and replicate the viral particles.
What does the cell cycle refer to?
What two phases does the cell cycle consist of and describe each one?
What is G1 phase of interphase?
Describe G1 phase of interphase?
What is S phase of interphase?
Describe S phase of interphase?
What is G2 phase of interphase?
Describe G2 phase of interphase?
What are the four (and one other) stages of mitosis?
The complete sequence of events in the life of an individual cell
Mitosis- cell division itself
Interphase- a period of cell growth and preparation for mitosis
G1 phase- first growth phase
- Protein synthesis, volume of cytoplasm increases, cell organelles produced
- A non dividing cell would remain here for many years
S phase- DNA synthesis phase
DNA replicates, ready for cell division
G2 phase- second growth phase
Further growth of cell, synthesis of proteins and creation of energy stores needed for mitosis
Prophase
Metaphase
Anaphase
Telophase and cytokinesis.
What are and describe the key events of prophase?
What are and describe the key events of metaphase?
What are and describe the key events of anaphase?
What are and describe the key events of telophase?
Prophase:
- Chromosomes start to condense (coil up and become visible under a light microscope)
- Pairs of identical chromatids are joined by centromeres
- Nucleolus disappears
- Nuclear envelope breaks down (to allow free movement of the chromosomes
- Centrioles appear
- Spindle fibres start to grow from centrioles
Metaphase:
- Chromosomes line up along centre (equator) of cell
- Spindle fibres attach to centromeres
Anaphase:
- Spindle fibres contract
- Chromatids separate and are pulled to the poles of the cell
Telophase:
- Chromatids reach the poles of the cell and start to de-condense (uncoil, become invisible under light microscope)
- Spindle fibres
- Nuclear envelope reforms
- Nucleolus reforms.
What are and describe the key events of cytokinesis?
What are centromeres?
What are chromatids?
What are two strands on the same chromosome called?
Cytokinesis (cell division):
- Cell membrane “squeezes in” (invaginates) and separates the two nuclei into two separate cells
- Goes back to G1 phase
The chromosomes are made of two strands joined together in the middle by a centromere
The separate strands of chromosomes are called chromatids
Two strands on the same chromosome are called sister chromatids.
What is each line numbered by on a stage micrometre?
What is the name for a ruler in the eyepiece of the microscope?
What is one unit on the eyepiece graticule equal to?
What is the equation for the calculating the value on the graticule?
What is mitotic index?
What is the equation for mitotic index?
What can cause cells to grow out of control?
What then happens and what does this form?
What is cancer?
What are some treatments for cancer designed to control?
How does it do this and what happens as a result?
What happens as a consequence?
Why are treatments more likely to kill tumour cells?
Each line is 1/10th of a mm, or 0.1 mm or 100 um
Graticule
0.625 um
Value of 1 unit on graticule = length on the stage micrometre -:- number of graticule units
The proportion of cells undergoing mitosis
Mitotic index= cells in mitosis -:- total number of cells X 100
A mutation in a gene that controls cell division
The cell keeps on dividing to make more and more cells forming a tumour
Cancer is a tumour that invades surrounding tissue
Designed to control the rate of cell division in tumour cells
By disrupting the cell cycle, killing the tumour cells
These treatments don’t distinguish tumour cells from normal cells- they also kill normal body cells that are dividing
Because tumour cells divide much more frequently than normal cells.
What happens in the following cell cycle targets of cancer treatments (full explanation):
G1 (cell growth and protein production)
S Phase (DNA replication)
What is mitotic index?
What is the formula for calculating mitotic index?
What is a haploid and give an example?
What is a diploid and give an example?
What is formed by the fusion of two haploid gametes?
Some chemical drugs (chemotherapy) prevent the synthesis of enzymes needed for DNA replication. If these aren’t produced, the cell is unable to enter the synthesis phase (S), disrupting the cell cycle and forcing the cell to kill itself
Radiation and some drugs damage DNA. At several points in the cell cycle, the DNA in the cell is checked for damage. If severe DNA damage is detected, the cell will kill itself- preventing further tumour growth
The proportion of cells undergoing mitosis
Mitotic Index= Cells in mitosis -:- Total number of cells X100
One copy of each type of chromosome (eg gametes)
Two copies of each type of chromosome (eg body cells)
A diploid zygote.
