B1- Cell Structure Flashcards
Equation Magnification
magnification = image size/ real object size
Definition Magnification
The number of times bigger the image is compared to the real object.
Definition Resolution
Smallest distance between two objects that can be distinguished.
What is order of magnitude?
A power to the base 10 used to quantify and compare size.
How does a light microscope work?
It passes a beam of light through a specimen, which travels through an eyepiece lens to be seen.
Advantages of light microscope (4)
- Inexpensive
- Easy to use
- Portable
- Lets you observe dead and living specimens
Disadvantage of light microscopes
Limited Resolution
How does an Electron microscope work?
Uses a beam of electrons which are focused using a magnet. The electrons hit a fluorescent screen which emits visible light, producing an image.
Two types of Electron Microscope
- Transmission Electron Microscope
- Scanning Electron Microscope
Advantages of Electron Microscope (2)
- Greater Magnification
- Higher Resolution
Why do Electron Microscopes have higher magnification and resolution?
Use a beam of electrons which have a shorter wavelength than photons of light.
How have Electron Microscopes enabled scientists to develop their understanding of cells? (2)
- Allows small sub-cellular structures to be observed in detail.
Disadvantages of Electron Microscope (4)
- Expensive
- Large making it less portable
- Requires training to use
- Only dead specimens can be seen
How many metres in a cm?
1 x 10^-2
How many metres in a mm?
1 x 10^-3
How many metres in a micrometre?
1 x 10^-6
How many metres in a nanometre?
1 x 10^-9
Differences between Prokaryotic and Eukaryotic (3)
- Prokaryotes are much smaller
- Prokaryotes contain free DNA (no nucleus)
- Prokaryotes may contain plasmids
What is the prokaryotic cell wall made of?
Peptidoglycan
What is the eukaryotic cell wall made of?
Cellulose (plants only)
How is genetic information stored in prokaryotic cells? (2)
- Plasmid DNA
- Chromosomal DNA (single loops)
Definition Plasmid
Small circular loops of DNA found free in the cytoplasm. That carry genes with genetic advances (antibiotic resistance)
List components of both plant and animal cell (5)
- Cytoplasm
- Mitochondria
- Ribosomes
- Nucleus
- Cell membrane
List components only in plant cell not human (3)
- Chloroplasts
- Cell wall
- Permanent Vacuole
Function of the Nucleus
- Controls cellular reactions and activities
- Stores genetic information
Structure of the Cytoplasm
Fluid (gel-like) component of the cell that contains organelles, enzymes and dissolved ions and nutrients.
Function of the Cytoplasm
Site of cellular reactions. Mode of transport in the cell.
Function of the Cell Membrane
Controls the materials that come in and out of the cell
Function of the Mitochondria
Site of later stages of aerobic respiration in which ATP is produced.
Function of the Ribosomes
Site of protein synthesis
Function of plant Cell Wall
Strengthens the cell and prevents the cell from bursting when water enters via osmosis.
What is inside of the permanent vacuole?
Cell Sap
Function of Permanent Vacuole
Supports the cell and keeps it turgid
Function of Chloroplasts
Site of photosynthesis
Adaptations of Sperm cell (4)
- Haploid nucleus (contains the genetic information)
- Tail that enables movement
- Mitochondria provides energy for tail movement
- Acrosome contains enzymes that digest the eggs cell membrane to fertilise the egg.
Adaptations of Nerve cells (3)
- Lots of dendrites that make connections to other cells
- Axons that carry the impulse from one place to another
- Synapses are adapted to pass the impulse to another cell or between a nerve cell and a muscle cell
Adaptations of Muscle cells (3)
- Contain proteins that slide over each other and make the fibres contract
- Contain many mitochondria to transfer energy needed for chemical reactions to take place
- Store glycogen, which can be broken down and used in cellular respiration by the mitochondria to provide energy needed for the fibres to contract.
Adaptations of Root Hair Cells (3)
- Increased surface area for water to move into the cell
- Permanent vacuole that speeds up movement of water by osmosis from the soil across the root hair cell
- Many mitochondria to transfer energy needed for active transport
Adaptations of Xylem Cells (2)
- Alive at first but die and form long hollow tubes to allow water and mineral ions to move easily through them
- Spirals is lignin make them very strong and help them to withstand pressure of water. Also help support phloem.
Adaptations of Phloem Cells
- Cell walls between the cells break down to form special sieve plates. Allow water carrying dissolved food to move freely
- Supported by companion cells which transfer energy and support them.
What is cell differentiation?
Process where cells become specialised
Why is cell differentiation important?
Allows production of different tissues and organs that perform various vital functions in the human body.
At what point in the the life cycle to cells differentiate in animal cells?
Early in their life cycle
How long to plants retain the ability to differentiate?
Throughout their whole life cycle.
What is the purpose of cell division in mature animals?
Repair and replacement of cells
What changes does a cell go through when differentiating?
It becomes specialised by acquiring different sub-cellular structures to enable the cell to carry out a specialised function.
How do bacteria multiply?
Binary Fission
How often do bacteria multiply?
If all factors aren’t limited then once every 20 minutes
Two ways bacteria can be grown
- Nutrient broth solution
- Colonies on an agar plate
What nutrients make up a nutrient broth?
All nutrients required for bacterial growth i.e. Nitrogen- protein synthesis, Carbohydrates- energy and other minerals
What are uncontaminated cultures of microorganisms needed for?
Investigating disinfectant and antibiotic action
Describe Aseptic technique needed for preparing an uncontaminated culture (6)
1- Use pre-sterilised plastic Petri dishes or sterilise glass Petri dishes and agar gel before using an autoclave.
2- Pour the sterile agar gel into the Petri Dish and allow time to set.
3- Sterilise the inoculating loop by passing it through a Bunsen burner flame.
4- Dip the inoculating loop into the solution of microorganisms and make streaks using the loop along the surface of the agar.
5- Put the lid on the the Petri Dish and secure it with tape. Label it accordingly then turn and store upside.
6- Incubate the culture at 25 Degrees Celsius in the labs.
Why must the Petri Dish be sterilised before use?
To kill any bacteria already present.
How do you kill any bacteria on the inoculating loop? (2)
- Pass it through the Bunsen burner flame
- Dip it into acid (HCL)
Why tape the lid down on the Petri dish?(2)
- To Stop bacteria in the air contaminating the culture.
- The lid isn’t fully sealed to avoid the growth of anaerobic bacteria in a lack of oxygen.
Why do we store the Petri Dish upside down?
To prevent condensation from forming and dripping down into the colonies.
Why incubate at 25 Degrees Celsius?
Harmful pathogens are less likely to grow at this temperature.
What is the inhibition zone?
Uniformly circular zone of no bacteria growth in an area contaminated with bacterium.
How to calculate effectiveness of antiseptic?
Area of circle = PI x r^2
