B1 Flashcards
What types of cells are eukaryotic? (2)
Plant and animal cells
What type of cells are prokaryotic?
Bacteria
What does a eukaryotic cell contain that a prokaryotic cell doesn’t?
It contains the genetic info in a nucleus.
What organelles do animal cells have and what do they do? (5)
- Nucleus - controls genetic info which controls activity cells. 2. Cytoplasm - where most chemical reactions occur (enzymes inside control the reactions. 3. Cell membrane - holds cell together and controls what enters and leaves. 4. Mitochondria - where respiration occurs. 5. Ribosomes - where protein synthesis occurs.
What organelles do plant cells have which animal cells don’t and what do they do? (3)
- Rigid cell wall - (made of cellulose) and supports and strengthens the cell. 2. Vacuole - contains cell sap (sugar and salts). 3. Chloroplasts - contains chlorophyll which absorbs sunlight for photosythesis.
What does a bacteria cell have? (5)
- Cytoplasm. 2. Cell membrane. 3. Cell wall. 4. Single strand of DNA which floats freely in cytoplasm. 5. Plasmids - small rings of DNA
Is a bacteria cell smaller than others?
Yes
Required practical activity 1: use a light microscope to observe, draw and label a selection of plant and animal cells. (5)
- Prepare slide by: adding water and then a layer of tissue and then iodine solution (to highlight objects in cells) and place a cover slip. 2. Click the slide onto the stage. 3. Select the lowest - powered objective lens and use the coarse adjustment know to move stage up. 3. Focus it using the fine adjustment. 4. Increase magnification with objective lens. 5. Draw a drawing in pencil (in proportion) with a scale and labels and title.
Magnification equation
Magnification is image size / actual size
What is differentiation?
The process by which a cell changes to become specialised for its job.
Why do cells differentiate in mature humans?
Repairing and replacing cells e.g. skin
How is sperm adapted to get to the woman’s egg? (3)
- It has a streamlined head and long tail to help it swim. 2. It has lots of mitochondria to give it energy. 3. It has enzymes to digest through the egg cell membrane.
How are nerve cells adapted for rapid signaling? (2)
- They are long (to cover more distance) 2. They have branched connections to connect with other nerve cells and form a network.
How are muscle cells adapted for quick contraction? (2)
- They’re long (so more space to contract) 2. Lots of mitochondria to generate energy for contraction.
How are root hair cells adapted for absorbing water and nutrients? (2)
- Large surface area. 2. Thin cell walls (to maximise diffusion)
How are xylem cells adapted for transporting water? (2)
- Strong walls. 2.Hollow (allows water through easily)
How are phloem cells adapted for transporting water? (2)
- Goes up and down (to transport products of photosynthesis). 2. Has companion cells which provide energy as it’s needed for transportation of substances.
Steps for mitosis (4)
- Subcellular structures doubled e.g. mitochondria. 2. DNA is doubled. 3. Chromosomes line up in the centre and split apart. 4. Cytoplasm and cell membranes divides to form 2 identical daughter cells.
Steps for binary fission (prokaryotic cells dividing) (4)
- Circular DNA and plasmids duplicate. 2. Circular DNA moves to opposite ends of cell. 3. Cytoplasm divides and new cell walls begin to form. 4. Each daughter cell has one copy of circular DNA and different number of plasmids.
How quickly can some bacteria divide?
Every 20 mins
What are the 2 different types of microscopes?
Light and electron
What is resolution with microscopes?
The ability to clearly distinguish the individual parts of an object.
What are the advantages of light microscopes? (5)
- Cheap. 2. Easy to use. 3. Portable. 4. Observes both dead and living specimens. 5. Colour
What are the advantages of electron microscopes? (2)
Higher magnification and higher resolution
What are the disadvantages of light microscopes? (2)
Limited magnification and limited resolution
What are the disadvantages of electron microscopes? (4)
- Large. 2. Not portable. 3. Can only see dead things. 4. Needs special training to use. 5. Only black and white
How has microscopy techniques changed over time?
Light microscopes were the original microscopes and a light and lenses were used to form an image of a specimen and magnify it. However the new electron microscope uses electrons instead of light to form an image.
How can bacteria be grown? (2)
Nutrient broth solution or as colonies on an agar gel plate.
Required practical activity 2: investigate the effect of antiseptics or antibiotics on bacterial growth using agar plates and measuring zones of inhibition. (5)
- Sterilise inoculating loop and transfer microorganism onto agar plate. 2. Place disks soaked with different types or concentrations of antibiotics into the agar plate - spaced apart. 3. Make sure you have a control which is soaked in sterile water. 4. Bigger inhibition zone means more (non - resistant) bacteria has died so more effective. 5. Leave the plate for 48 hours at 25 degrees.
Why must Petri dishes and culture media must be sterilised before use?
To kill unwanted pathogens so it doesn’t affect the results.
Why and how are inoculating loops sterilised?
To kill unwanted pathogens by passing it through a hot flame.
Why must the lid of the Petri dish be secured with adhesive tape?
To stop any microorganisms entering (from the air).
Why must the lid of the Petri dish be stored upside down?
Stop drops of condensation from falling onto the agar surface.
In school labs, why must cultures generally be incubated at 25°C?
Harmful pathogens are more likely to grow.
How do you work out the inhibition zone?
πr²
How are chromosomes usually found in the body?
In pairs
What is a stem cell?
Undifferentiated cell of an organism
What illnesses can stem cells help? (2)
Diabetes and paralysis
What is the function of stem cells from embryos?
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
What is the function of stem cells from adult bone marrow?
Stem cells from adult bone marrow can form many types of cells including blood cells.
What is the function of stem cells from meristem tissue in plants?
Meristem tissue in plants can differentiate into any type of plant cell throughout the life of the plant.
What are advantages of stem cells from embryos? (2)
Not rejected by the patient’s body, can differentiate into any cell so very useful
What are disadvantages of stem cells from embryos? (2)
Ethical issues and risk of infection from surgery
What are advantages of stem cells from adult bone marrow? (2)
No ethical issues and differentiates into some cells.
What are disadvantages of stem cells from human bone marrow? (4)
Only differentiates into some cells and risk of infection and risk of rejection and painful procedure
What are advantages of stem cells from meristem tissues in plants? (2)
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 disadvantages of stem cells from meristem tissues in plants? (1)
Only found in some areas of the plant.
What is diffusion?
The movement of particles from an area of high concentration to an area of low concentration. It does not require energy.
What are 2 examples of when diffusion occurs in animals?
In the lungs (where oxygen and carbon dioxide in gas exchange) and in the liver where the waste product urea goes from cells into the blood plasma for excretion in the kidney.
What is an example when diffusion occurs in plants?
Carbon dioxide entering the plant and oxygen leaving
What are 3 factors that affect diffusion?
The difference in concentrations (concentration gradient) and temperature and surface area to volume ratio of the membraneHow
How does the concentration gradient affect the rate of diffusion?
The greater the difference in concentration and the quicker the rate of diffusion.
How does temperature affect the rate of diffusion?
The higher the temperature, the more kinetic energy the particles will have so they will move and mix more quickly.
How does surface area (of the cell membrane) to volume ratio affect the rate of diffusion?
The greater the surface area and the faster the rate of diffusion.
How is the small intestine adapted for exchanging materials? (3)
- Has villi and microvilli. This increases the surface area for transport. 2. It has a very rich blood supply to increase the rate of diffusion 3. Short diffusion path (thin cell wall)
How are the lungs adapted for exchanging materials? (4)
- Alveoli gives large surface area. 2. Short diffusion path (thin cell wall) 3. Good blood supply. 4. Moist walls
How are the gills in fish adapted for exchanging materials? (3)
- Lots of thin gill filaments which means large surface area (to volume ratio). 2. Short diffusion path (thin cell walls). 3. Good blood supply
How are the roots and leaves in plants adapted for exchanging materials? (2)
- Rots have a large surface area to volume ratio. 2. Short diffusion path (thin cell wall)
What is osmosis?
Osmosis is the diffusion of water from a high concentration (of water) to a low concentration across a semi - permeable membrane. It does not require energy.
Required practical activity 3: investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue. (5)
- Cut up potato into identical cylinders and measure mass 2. Get beakers with water, and different concentrations of sucrose solution. 3. Leave potatoes in cylinder for 24 hours and pat dry and measure masses. 4. Calculate percentage change - if the potato is heavier, then osmosis has drawn in water. 5. Repeat experiment and find a mean mass change.
What is active transport?
Active transport moves substances from a low concentration to a high concentrated solution (against a concentration gradient). This requires energy from respiration.
How does active transport work in root hair cells?
It takes up water and mineral ions from the soil and enters the cell (which usually has a high concentration already there).
How does active transport work in the gut?
It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
