Topic 1: Cell Biology Flashcards
What do both plant and animal cells have? [5]
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
What extra structures do plant cells have? [3]
- Cell wall
- Permanent vacuole
- Chloroplasts
What structures do prokaryotic cells have? [5]
- Cytoplasm
- Cell membrane
- Cell wall
- Circular strand of DNA
- Plasmids
How do light microscopes from an image?
They use light and lenses to form an image and magnify it
What do light microscopes allow us to see? [2]
- Individual cells
- Large subcellular structures e.g. nuclei
How do electron microscopes allow us to see more sub-cellular structures? [3]
- An electron microscope has a much higher magnification and resolving power than a light microscope
- This means it can be used to study cells in much finer detail
- This allows us to see and understand more sub-cellular structures
What is the equation for magnification?
Magnification = size of image/size of object
Define ‘differetiation’
Process by which a cell changes to become specialised for its job
When does differentiation usually occur in an organism?
As it develops
When do most animal cells lose the ability to differentiate?
At an early stage, after they become specialised
Do most plant cells lose the ability to differentiate?
No
In mature animals, what is differentiation mainly used for?
Repairing and replacing cells
Name an undifferentiated cell in animals
Stem cells
Write and check
How is a sperm cell adapted? [3]
- Long tail and streamlined body - help it swim to the egg
- Lots of mitochondria - to provide them with energy from respiration
- Digestive enzymes in head - break into the egg cell membrane
Write and check
How is a nerve cell adapted? [2]
- Long - cover more distance
- Branched connections - connect to other nerve cells and form a network
Write and check
How is a muscles cell adapted? [2]
- Long - space to contract
- Lots of mitochondria - provides them with the energy they need
How is a root hair cell adapted? [2]
- Lots of hairs
- Large surface area
How are phloem cells adapted? [1]
Very few subcellular structures - allows stuff to flow through
How are xylem cells adapted? [1]
Hollow - allows stuff to flow through
Where are chromosomes found?
In the nucleus
What are chromosomes made from?
DNA molecules
What are found on chromosomes?
Genes
Why do chromosomes normally come in pairs?
One copy from the mother and one copy from the father
Write and check
Describe the stages of mitosis [5]
- Growth - the cell grows and increases the amount of subcellular structures it has (mitochondria and ribosomes)
- DNA Replication - the cell duplicates its DNA. The DNA is copied and forms x-shaped chromosomes. Each arm is an exact duplicate of the other
- Mitosis - the x-shaped chromosomes line up along the centre of the cell and cell fibres pull them apart - the two arms of each chromosome go to opposite sides of the cell
- The nucleus divides
- Division - the cell membrane and cytoplasm pull apart to form two new daughter cells
What do multicellular organisms use mitosis for? [3]
- Growth
- Development
- Repair
What is the role of the nucleus?
It contains genetic material that controls the activities of the cell
What is the role of the cytoplasm?
It is a gel-like substance where chemical reactions occur
What is the role of the cell membrane?
Holds the cell together and controls what goes in and out
What is the role of the mitochondria?
It is the site of aerobic respiration which releases energy for the cell to use
What is the role of ribosomes?
Site of protein synthesis
What is the role of the cell wall?
Supports and strengthens the cell
What is the cell wall made from?
Cellulose
What is the role of the permanent vacuole?
Contains a weak salt and sugar solution called cell sap
What is the role of chloroplasts?
Site of photosynthesis which makes food for the plant
What do chloroplasts contain?
Chlorophyll
What are plasmids?
Small rings of DNA
What kind of division do prokaryotic cells divide by?
Binary fission
Write and check
Describe the stages of binary fission [6]
- The cells grows
- The circular DNA and plasmids replicate
- Circular DNA strands move to opposite ends of the cell
- Cytoplasm begins to divide and new cell wall begins to form
- Cytoplasm divides and two new daughter cells are produced
- Each daughter cell has one copy of the circular DNA but can have a differing number of plasmids
How often can bacteria multiply in the correct conditions?
Once every 20 mins
In what 2 ways can bacteria be grown?
- Nutrient broth solution
- Colonies on an agar gel plate
RP 2: aseptic techniques
Why must petri dishes and culture media be sterilised before use? [2]
- To kill unwanted microorganisms
- To prevent them affecting the results
RP 2: aseptic techniques
Why must the inoculating loop be sterilised by passing through a flame? [2]
- To kill unwanted microorganisms
- To prevent them affecting the results
RP 2: aseptic techniques
Why must the lid of the petri dish be secured with adhesive tape? [2]
- To stop the lid falling off
- Stop any unwanted microorganisms entering
RP 2: aseptic techniques
Why must the petri dish be stored upside down?
Stops moisture from dripping down onto the bacteria and disrupting the colonies
RP 2: aseptic techniques
In school, why should we not incubate bacteria above 25°C?
Reduces the chances that harmful bacteria will grow
What is a stem cell?
An undifferentiated cell
What can embryonic stem cells do?
Differentiate into any type of human cell
Where are adult stem cells found?
Bone marrow
What kind of cells can adult stem cells differentiate into?
Blood cells
Where are stem cells in plants found?
Meristems
How long can plant stem cells differentiate for?
Plant’s entire life
What are plant stem cells used for? [2]
- Rare species can be cloned to protect from extinction
- Plant species with special features can be cloned to produce large numbers of identical plants
What kind of conditions could embryonic stem cells be used to treat? [2]
- Diabetes
- Paralysis
What is therapeutic cloning?
An embryo is produced with the same genes as a person. Therefore, stem cells from the embryo are not rejected
What is the risk involved with stem cells in medicine?
Transfer of viral infections
Why are some people against stem cell research?
Human embryos shouldn’t be used for experiments since each one has the potential for human life
What are the arguments for stem cell research? [2]
- Curing suffering existing patients is more important than the rights of embryos
- The embryos used are unwanted ones from fertility clinics - would otherwise be destroyed
Is stem cell research allowed in the UK?
Yes, but it has to follow strict guidelines
What is diffusion?
The net movement of particles from an area of higher concentration to an area of lower concentration
How does the concentration gradient affect the rate of diffusion?
The bigger the concentration gradient, the higher the rate of diffusion
How does temperature affect the rate of diffusion?
The higher the temperature, the higher the rate of diffusion
How does surface area affect the rate of diffusion?
The larger the surface area, the higher the rate of diffusion
Which molecules does the cell membrane allow/not allow to diffuse across? [2]
- Small molecules can diffuse through the membrane (e.g. oxygen, glucose, amino acids and water)
- Big molecules can’t diffuse through the membrane (e.g. starch and proteins)
What is osmosis?
The net movement of particles, across a partially permeable membrane, from an area of higher water concentration to an area of lower water concentration
What is active transport?
The movement of molecules against their concentration gradient, from an area of lower concentration to an area of higher concentration, across a cell membrane
What does active transport require?
Energy from respiration
How does active transport allow mineral ions to be absorbed by plant roots?
It allows roots to absorb minerals from a low concentration in the soil to a high concentration in the plant
What are mineral ions needed for in plants?
Healthy growth
How does active transport allow the blood to absorb sugar molecules?
It allows the blood to absorb sugar molecules from a lower concentration in the gut to a higher concentration in the blood
What are sugar molecules need for in animals?
Cellular respiration
What happens to SA:volume ratio as organisms get larger?
It decreases
Why can small organisms (e.g. bacteria cell) rely on diffusion?
They have a large SA:volume ratio so enough substances can be exchanged across the membrane to meet the needs of the organism
Why can multicellular organisms not transport substances by diffusion?
Their SA:volume ratio is too low
What do multicellular organisms have to fix the problem of ineffective diffusion? [2]
- Exchange surfaces
- Transport systems
How are exchange surfaces adapted to maximise effectiveness? [4 ways]
- Thin membranes - short diffusion path
- Large SA
- Efficient blood supply
- Ventilation
What is the job of the lungs? [2]
- To transfer oxygen to the blood
- To removed waste CO₂ from the blood
What do the lungs contain for gas exchange?
Alveoli
How are alveoli specialised to maximise diffusion? [4]
- Big SA
- Moist lining - for dissolving gases
- Thin walls
- Good blood supply
What do the small intestines contain for exchange?
Villi
How are villi specialised to maximise food absorption into the blood? [2]
- Single layer of surface cells
- Good blood supply
How are leaves specialised to maximise CO₂ absorption? [2]
- Large SA
- Thin surface
How are gills in fish specialised to maximise exchange? [4]
- Lots of gill filaments - large SA
- Gill fillaments covered in lamellae - increases SA further
- Lamellae have a good blood supply
- Gill filaments have thin surface layer
How do you move from millimetres to micrometres?
x 1,000
How many chromosomes will each nucleus have after undergoing mitosis?
The same amount as the parent nucleus
In general, why should students repeat their investigation? [2]
- To check for anomalies
- To improve the reliability
