4.1.1 Cell structure Flashcards
What do plant and animal cells (eukaryotic cells) have in common?
Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.
How are bacterial cells (prokaryotic cells) different from eukaryotic cells?
- Bacterial cells (prokaryotic cells) are smaller.
- They have cytoplasm and a cell membrane surrounded by a cell wall.
- The genetic material is not enclosed in the nucleus, it is a single DNA loop and there may be one or more small rings of DNA called plasmids.
What do most animal cells have in common?
- A nucleus
- Cytoplasm
- A cell membrane
- Mitochondria
- Ribosomes
In addition to the parts found in animal cells, plant cells often have…?
- Chloroplasts
- A permanent vocuole with cell sap
What do plant and algal cells have that strengthens them?
Plant and algal cells also have a cell wall made of cellulose, which strengthens the cell.
What functions may animal and plant cells be specialised to carry out?
- In animal cells, sperm cells, nerve cells and muscle cells.
- In plant cells, root hair cells, xylem cells and phloem cells.
What happens to cells as an organism develops, and how does this process differ between plant and animal cells?
As an organism develops, cells differenciate to form different types of cells.
* most types of animal cells differenciate at an early stage.
* most types of plant cells retain the ability to differentiate throughout life.
What is the primary purpose of cell division in mature animals, and what happens to cells as they differentiate?
In mature animals, cell division is mainly for repair and replacement. As cells differentiate, they develop specific sub-cellular structures to perform specialized functions.
Why is an electron microscope more effective than a light microscope for studying cells?
An electron microscope offers much higher magnification and resolving power than a light microscope, allowing biologists to study cells in greater detail and understand more sub-cellular structures.
Magnification formula
magnification=
size of image/size of real object
How do bacteria multiply, and how frequently can this process occur under optimal conditions?
Bacteria multiply by simper cell division (bianary fission) as often aqs once every 20 minutes if they have enough nutrients and a suitable temperature.
What are the two methods for growing bacteria?
bacteria can be grown in a nutrient broth solution or as colonies on an agar gel plate.
What is necessary for investigating the action of disinfectants on microorganisms?
Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants.
What are the 4 optimal conditions for bacterial growth?
- Temperature - most bacteria grow fastest in warm environments.
- Nutrient availability - bacteria need a good supply of nutrients in order to grow rapidly.
- Moisture - most bacteria grow fastest in moist conditions.
- Oxygen - different types of bacteria either need the presence or absence of oxygen for growth.
Why must petri dishes and culture media be steralised before use?
- Prevent Contamination: Eliminates unwanted microorganisms.
- Ensure Accurate Results: Guarantees that observed growth is solely due to the intended organism.
- Promote Reproducibility: Allows consistent results across experiments.
- Minimize Safety Risks: Reduces exposure to potentially harmful pathogens.
How to prepare an uncontaminated culture using antiseptic technique?
- Clean Workspace: Disinfect the work surface.
- Wear Protective Gear: Use gloves and a lab coat.
- Sterilize Equipment: Flame sterilize the inoculating loop.
- Open Petri Dish: Do it quickly and at an angle.
- Inoculate Culture: Streak sample onto agar using the cooled loop.
- Seal Petri Dish: Close immediately to prevent contamination.
- Label Dish: Write the date and type of culture on the bottom.
- Incubate Culture: Place dish upside down in an incubator.
- Check for Contamination: Observe for unwanted growth; dispose of contaminated cultures safely.
Why do inoculating loops used to transfer microorganisms to the media have to be sterilised by passing them through a flame?
- Kill Contaminants: Flame destroys unwanted microorganisms.
- Maintain Aseptic Technique: Prevents culture contamination.
- Prevent Cross-Contamination: Avoids transferring microbes between cultures.
- Ensure Safety: Reduces risk of spreading pathogens.
Why does the lid of the petri dish need to be secured with adhesive tape and stored upside down?
- Prevent Contamination: Tape secures the lid against airborne microbes.
- Minimize Evaporation: Upside-down storage prevents condensation on agar.
- Maintain Sterility: Keeps a sterile environment for growth.
Why in school laboratories should cultures generally be stored at 25 degrees Celsius?
- Optimal Growth: Many microorganisms grow best at 25°C.
- Safety: Reduces the risk of harmful pathogens.
- Controlled Environment: Easy to maintain in school labs.
How do you calcut\late the cross-sectional areas of colonies or clear areas around colonies?
area=πr2
How to calculate the number of bacteria in a population after a certain time if given the mean division time?
To Calculate Number of Bacteria:
Formula:
N = N^0 x 2^(t/d)
-
Where:
- N = final number of bacteria
- N^0 = initial number of bacteria
- t = total growth time
- d = mean division time
