Topic 2A: Cell Structure and Division Flashcards
1
Q
Cell membrane
A
- Regulates movement of substances in and out of the cell
- Have receptors to respond to chemicals e.g. hormones
2
Q
Nucleus
A
- Nuclear envelope = double membrane with pores
- Holds chromosomes –> protein bound DNA
- Controls cell activity
- Nucleolus - makes ribosomes
3
Q
Mitochondria
A
- Double membrane –> inner folded to make cristae
- Matrix = inside the membranes = has enzymes for respiration
- Does aerobic respiration for ATP
4
Q
Chloroplast
A
- Double membrane
- Thylakoid membranes inside –> stack to make grana –> linked by lamellae (thin, flat pieces of thylakoid)
- Does photosynthesis –> some in grana, some in stroma
5
Q
Golgi apparatus
A
- Fluid filled, membrane bound, flattened sacs
- Process and package lipids and proteins
6
Q
Vesicles
A
- Smaller sacs around Golgi
- Stores lipids and proteins and transports them out of the cell
7
Q
Lysosome
A
- Type of Golgi vesicle
- Has lysozymes that digest invading cells or worn out cell parts
8
Q
Ribosome
A
- Float free or on RER
- Made of proteins and RNA
- Does protein synthesis
- Not surrounded by a membrane
9
Q
Rough Endoplasmic Reticulum
A
- System of membranes covered in ribosomes
- Folds and processes proteins made by ribosomes
10
Q
Smooth Endoplasmic Reticulum
A
- No ribosomes
- Synthesises and processes lipids
11
Q
Cell wall
A
- Cellulose in plants
- Chitin in fungi
- Supports cell and stops it changing shape
12
Q
Vacuole
A
- Contains cell sap –> sugar and salt solution
- In membrane - tonoplast
- Maintains pressure in plant cells
- Isolates unwanted chemicals
13
Q
What are prokaryotic cell walls made of?
A
Murein
14
Q
Slime capsule
A
- Protects them from attack by the immune system
15
Q
Plasmid
A
- Small DNA loops containing specific genes
- Can be passed between cells
- Not always present
16
Q
Circular DNA
A
- No nucleus –> DNA floats free
17
Q
Cytoplasm in prokaryotes
A
- Holds no membrane bound organelles
18
Q
Ribosomes in prokaryotes
A
- Much smaller than in eukaryotes
- 70s
19
Q
Flagella
A
- Long hair-like structure
- Rotates to allow the cell to move
20
Q
Describe the process of binary fission
A
- Circular DNA and plasmids replicate –> circular only once, plasmids can replicate multiple times
- Cell grows –> DNA loops move to opposite ends
- Cytoplasm begins to divide + new cell walls begin to form
- Cytoplasm divides and 2 daughter cells produced –> each has one circular DNA and a variable number of plasmids
21
Q
How are viruses structured?
A
- Core of genetic info (DNA / RNA)
- In a protein coat (capsid)
- Attachment proteins –> allow virus to attach to a host cell
22
Q
Describe virus replication
A
- Virus attach attachment proteins to complimentary receptor proteins on the host cell surface –> some viruses can only infect one type of cell
- They inject the host cell with their DNA / RNA and use its own parts to reproduce
23
Q
Define magnification
A
How much bigger an image is than the specimen
24
Q
Define resolution
A
How detailed an image is –> how easy it is to distinguish between two points
25
Q
What is the equation for magnification?
A
Magnification = image size / actual size
26
Q
Light microscopes
A
- Use light to form an image
- Max resolution = 0.2 micrometres –> can see nucleus
- Max mag = x1500
- Can view live specimens
- Can see in colour
27
Q
Electron microscopes
A
- Use electrons to form an image
- Higher resolution –> 0.0002 micrometres
- Max mag = 1,500,000
- Black and white images only
- Specimens must be dead
28
Q
Transmission Electron Microscopes
A
- Transmit a beam of electrons through the sample
- Denser parts absorb more –> look darker
- Has high resolution –> can see internal structure of organelles
- Can only be used on thin specimens
29
Q
Scanning Electron Microscopes
A
- Scan a beam of electrons over specimen knocking off electrons from the specimen –> collected in cathode ray tube to make the image
- 3D image
- Can be used on thicker specimens
- Lower resolution
30
Q
What are microscope artefacts?
A
- Things you can see down a microscope that are not parts of the cell e.g. fingerprints, bubbles, dust
31
Q
Describe homogenisation and conditions needed
A
- Vibrate or grind cells to break membrane and release organelles
- Ice cold –> reduces enzyme activity to stop organelles being broken down
- Isotonic –> same conc in and out to prevent damage to organelles by osmosis
- Buffer solution –> maintains pH
32
Q
Desrcibe filtration of cell components
A
- Filtered through a gauze to remove large cell / tissue debris
33
Q
Describe ultracentrifugation
A
- Cell fragments in solution spun in centrifuge
- Heaviest organelles flung to the bottom = pellet
- Suspended organelles = supernatant
- Supernatant drained off + spun again
- Repeated to separate all organelles
- Nuclei, chloroplasts (if present), mitochondria, lysosomes, RER + SER, ribosomes
34
Q
Describe interphase
A
- G1= cell grows and new proteins and organelles are made
- S = DNA replicates
- G2 = cell keeps growing + proteins needed for mitosis are made
35
Q
What is mitosis used for?
A
Growth and repair
36
Q
Describe the stages of mitosis
A
- Prophase –> chromosomes condense, centrioles move to opposite ends and form spindles, nuclear envelope breaks down
- Metaphase –> Chromosomes line up down the middle + spindles attach to centromere
- Anaphase –> Centromeres divide and sister chromatids separate, spindles contract pulling chromatids to opposite ends
- Telophase –> Sets of chromosomes collect at opposite ends, new nuclear membranes form, chromosomes become long and thin again, cytoplasm divides
37
Q
What is cancer?
A
- Uncontrolled cell growth due to a gene mutation
- Cell division stops responding to normal regulations so cells rapidly divide
- Cells clump to form tumours
38
Q
What are benign tumours?
A
- Divide at a normal rate, don’t invade other tissues
- Usually harmless but can press on other organs and impact their function
- If needed they can be surgically removed
39
Q
What are malignant tumours?
A
- Divide rapidly and interfere with organ functions
- Invade other tissues via metastasis
- Parts can break off and travel round the body to form secondary growths making it very harmful and difficult to treat
40
Q
What are come causes of cancer?
A
- Genetics e.g. BRCA1+2
- Radiation exposure –> including UV
- Substances e.g. smoking, alcohol
41
Q
What are some treatments for cancer?
A
- Chemotherapy –> prevents synthesis of enzymes needed in DNA replication to stop the cell cycle –> usually drugs that target quick dividing cells
- Radiotherapy –> can damage DNA so it doesn’t make it past checkpoints preventing cell cycle
- Surgery
- Drugs –> can prevent spindle fibres forming to prevent mitosis
42
Q
Describe the root tip squash practical.
A
- Cut 1cm tip off the root
- Put HCl in a test tube in a water bath at 60 degrees
- Put the tip in the acid and leave for 5 mins
- Pipette rinse the tip with water and dry
- Cut 2mm of the tip off and put on a microscope slide
- Use a mounted needle to break the tip open and spread the cells thinly
- Add a stain to make the chromosomes easier to see
- Place a cover slip over and push down on top to squash the tissue
- Observe with a microscope
43
Q
What is the calculation for mitotic index?
A
mitotic index = number of cells with visible chromosomes / total number of cells observed
