B1 - Cell Biology Flashcards
What are the two types of cell?
Eukaryotic and prokaryotic
Compare eukaryotic and prokaryotic cells
Eukaryotes contain membrane-bound organelles and a nucleus
Prokaryotes have genetic information as single DNA loops, enclosed in plasmids or free floating in the cytoplasm
Both make up living things
Eukaryotic cells divide by mitosis
Prokaryotic cells divide by binary fission
Eukaryotes are larger than prokaryotes
Both contain a cell wall in plants, cytoplasm and ribosomes
What is order of magnitude?
A power to the base 10 used to quantify and compare size
What is the function of the nucleus?
Controls and regulates cell activity. Contains the genetic material.
What is the function of the cytoplasm?
The site where chemical reactions occur
What is the function of the cell (plasma) membrane?
Regulates the cell’s biochemistry; what substances enter and leave the cell
What is the function of the mitochondria?
Site of aerobic respiration, which releases energy in the form of ATP
What is the function of ribosomes?
Site of protein synthesis
What is the function of the cell wall?
Made of cellulose. Provides strength and prevents the cell from bursting due to osmotic stress
What is the function of the permanent vacuole?
Supports the cell by regulating water balance, maintaining its turgidity. Contains cell sap
What is the function of the chloroplasts?
The green pigment chlorophyll in the chloroplast absorbs light energy for photosynthesis
How are sperm cells adapted to their function?
Acrosome in the head, which allows for the cell to penetrate the outer membrane of the ovum for fertilisation
High yield of mitochondria for movement
Haploid nucleus, which contains the genetic information
Tail and stream-lined body for movement
How are nerve cells adapted to their function?
Long axons, which allow for electrical impulses to be transmitted rapidly all over the body from the CNS
Dendrites to connect with other neurones, forming a complex network
Axon is covered with a fatty Myelin Sheath, which speeds up nerve impulses
How are muscle cells adapted to their function?
High yield of mitochondria so that the muscle can contract and relax
Protein fibres that allow them to slide over each other to produce muscle contraction
How are root hair cells adapted to their function?
Large surface area for water and mineral absorption by osmosis or active transport
Thin walls so that water absorption is not restricted
What is cell differentiation?
When cells become specialised to perform a particular function
Why is cell differentiation important?
Allows for the production of various tissues and organs that perform different functions in the human body
At what point in their life cycle do most animal cells differentiate?
Early in their life cycle
How long do plant cells retain the ability to differentiate?
Throughout their entire life cycle
What is the purpose of cell division in mature animals?
Repair and replacement of cells
What changes does a cell undergo as it differentiates?
Acquires different sub-cellular structures to adapt the cell to perform a particular function
Advantages of light microscopes? (4)
- Portable
- Affordable/cheaper
- Easy to use
- Observe living and dead specimens
What are two disadvantages of using light microscopes?
Limited resolution and magnification
What are two advantages of electron microscopes?
Greater magnification and resolution
Why do electron microscopes have a greater magnification and resolution?
Use a beam of electrons, which have a shorter wavelength than photons of light
Why are electron microscopes more efficient for scientists?
Allows for sub-cellular structures to be observed in detail and hence, derive explanations as to why structure relates to function
Disadvantages of electron microscopes? (4)
- Expensive
- Less portable
- Require training to use
- Only dead specimens can be observed
Magnification equation
Magnification = image size/actual size
Remember I AM
How do bacteria multiply?
Binary fission
How often do bacteria multiply?
Once every 20 mins IF enough nutrients are available and the temperature is suitable for growth
What two ways can bacteria be grown?
Using a nutrient broth solution
As colonies on an agar gel plate
What are uncontaminated cultures of microorganisms needed for?
Investigating disinfectant and antibiotic action
Design a method for the preparation of an uncontaminated culture using aseptic technique (6)
Why must petri dishes and culture media be sterilised before use?
To kill any bacteria/microbes that are present already
Why must inoculating loops be sterilised by passing them through a Bunsen Burner flame?
To kill any bacteria/microbes present already
Why must a Petri dish be secured with tape and stored upside down? (3)
Stops bacteria/microbes in the air contaminating the culture
Lid is not fully sealed to prevent the growth of anaerobic bacteria
Upside down to prevent condensation from forming and dripping down onto the colonies
Why are cultures incubated at 25C in school laboratories?
Harmful pathogens are less likely to grow at this temperature
What is the formula used to calculate cross-sectional areas of colonies or clear areas around colonies?
𝝅 r 2
radius = diameter/2
How would you calculate the number of bacteria in a population after a certain time if given the mean division time?
M —> cm —-> mm —> picometre —> nanometre
X100
X10
X1000
X1000
What is the function of:
- Sperm cells
- Muscle cells
- Nerve cells
- Root hair cells
The function of sperm cells is reproduction; to fertilise the ovum
The function of muscle cells is contraction
The function of nerve cells is to carry electrical signals from one part of the body to another
The function of root hair cells is to absorb water and mineral ions
What is the function of phloem tissue?
Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage. This is otherwise known as translocation
What is the function of xylem tissue?
Transports water and mineral ions from the roots to the stem and leaves
How is the phloem adapted to its function?
How is the xylem adapted to its function?
Define the following terms:
- Culture medium
- Agar jelly
- Inhibition zone
A culture medium is liquid/gel substance that contains nutrients in which microorganisms, cells and tissues are grown
Agar jelly is a substance that helps feed and grow bacteria
Inhibitions zone is a clear area left where the bacteria have been killed by the antibiotic. Bigger zone means the antibiotic is more effective
Explain how the shape of the red blood cells in a person with sickle cell disease could affect how much oxygen reaches their muscles
Red blood cells carry oxygen
Red blood cells contain haemoglobin, which binds to oxygen
A person with sickle cell has smaller RBCs, so they contain less haemoglobin and less oxygen is carried
It has a smaller surface area to volume ratio, so diffusion is slower and so less oxygen is delivered per minute
Compare the processes of diffusion, active transport and diffusion
Scientists have developed patches of beating heart cells to repair damaged heart tissue
The patches are placed onto areas of the heart where cells have died. New cells grow to replace the dead cells. The patches are made using a person’s own cells that are converted into stem cells.
Explain why stem cells are used to make the patches
Stem cells are undifferentiated cells
So they can differentiate to form heart cells
Describe a method to investigate the effect of antiseptics or antibiotics on bacterial growth using agar plates and measuring zones of inhibition
Clean bench with disinfectant to kill microorganisms
Sterilise inoculating loop to prevent contamination
Place sterile agar gel plate near Bunsen burner to kill bacteria
Use inoculating loop to spread bacteria evenly over the plate
Place sterile filter paper disks soaked in chosen antibiotic. Use a paper disk soaked in water as a control to ensure the inhibition zones are due to the effects of the antibiotics alone
Store the plate with adhesive tape, upside down
Leave the plate for 48 hours at 25C
Measure the zone of inhibition using the equation of the area of a circle and use this to compare the effectiveness of the antibiotics/antiseptics
Define cell cycle
Series of stages in which a cell divides
How many chromosomes does the human body contain?
Describe the stages of mitosis
Human body cells contain 23 pairs of chromosomes
- DNA replicates to form two copies of each chromosome. The number of sub-cellular structures increases
- One set of chromosomes is pulled to each end (poles) of the cell (by the use of spindle fibres). The nucleus divides to form two nuclei
- In cytokinesis the cytoplasm and cell membrane divide to form two genetically identical daughter cells
What is a stem cell?
Undifferentiated cell which can give rise to many more cells of the same type and differentiate into certain other cells
How can stem cells from human embryos be used?
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells
How can stem cells from adult bone marrow be used?
Stem cells from adult bone marrow can differentiate and form many types of cells, including blood cells
How can meristem tissue be used?
Meristem tissue can differentiate into any type of plant cell throughout the life of the plant
What are two examples of treatments that stem cells can give rise to?
They may be able to help in conditions such as diabetes and paralysis
What is therapeutic cloning?
Producing an embryo with the same genes as the patient
Stem cells from embryo is then simulated to divide to form any cells the patient needs for medical treatment.
What is the advantage of therapeutic cloning?
Stem cells are unlikely to be rejected by the patient’s immune system
What are some issues associated with the use of stem cells in medicine?
Viral infections may be transferred
risk of rejection by the immune system, so patients have to take immunosuppressants drugs
Ethical and religious objections, for example, potential life is destroyed and the embryo cannot give consent
Describe the stem cells in plants
Meristem tissue is found in meristem regions in roots and shoots tips
This can differentiate into any type of plant cell throughout of plants lifetime
How can stem cells from meristems in plants be used?
Rare species can be cloned to protect from extinction
Crop plants with special features, such as disease resistance, can be cloned to produce large numbers of identical plants for farmers
What are the factors affecting the rate of diffusion?
Concentration, surface area and temperature
Describe how to prepare and observe a microscope to view cells
Peel off thin layer of tissue using forceps and place a drop of water on the slide/swab inside cheek with a cotton bud and smear into the centre of the slide
Add a drip of stain with a pipette and lower coverslip at an angle without trapping air bubbles
Clip slide onto the stage and turn on the light
Select the lowest power objective lens
Use coarse focusing dual to move stage close to the lens
Turn the coarse focusing dial to move stage away from the lens until image comes into focus
Adjust fine focusing wheel to get a clear image, swap to a higher power objective lens and refocus
