B1 - Cell Biology Flashcards
What are eukaryotic cells?
Complex cells, animal and plant cells.
What is the nucleus of a plant cell?
It contains genetic material and controls the activities of the cell.
What is a cytoplasm?
It’s a gel like substance, containing enzymes, where most chemical reactions take place.
What is a cell membrane?
The barrier to the cell, it holds it together and controls what goes in and out.
What is the mitochondria?
Where the reactions for aerobic respiration take place.
What is a ribosome?
It is where proteins are made.
What is a cell wall?
It supports the cell and strengthens it. It’s made of cellulose.
What is a permanent vacuole?
Contains cell sap: a weak solution of sugar and salts.
What are chloroplasts?
They contains green substance called chlorophyll which is needed for photosynthesis. They are also where photosynthesis occurs.
What type of cells are bacteria?
Prokaryotic
What do bacteria cells have instead of a nucleus?
A strand of DNA floating freely in the cytoplasm, and sometimes rings of DNA called plasmids
What are microscopes?
Devices that allow us to get a magnified image of something we couldn’t see with the naked eye
What do light microscopes use to form an image?
Light and lenses
What do electron microscopes use to form an image?
Electrons
Do electron or light microscopes have a higher magnification?
Electron
Do electron or light microscopes have a higher resolution?
Electron
What is resolution?
The ability to distinguish between two points, a sharper image
Magnification =
Image size/real size
What is a slide?
A clear strip of plastic or glass that you put the specimen on
What is the first thing you do in preparing a slide? (Onion)
Add a drop of water to the centre of the slide
What is the second thing you do in preparing a slide? (Onion)
Using tweezers, take a thin layer of the onion
What is the third thing you do in preparing a slide? (Onion)
Place the thin onion layer on the water droplet on the slide
What is the fourth thing you do in preparing a slide? (Onion)
Add a drop of iodine solution
What is the fifth thing you do in preparing a slide? (Onion)
Place a cover slip over the specimen
Why do you add iodine to a slide?
To stain the specimen
How do you place the cover slip on the slide?
Stand it upright on one edge, then tilt and lower it until it covers the specimen
Which lens do you use first on a light microscope?
The lowest powered objective lens
What does the coarse adjustment knob do on a light microscope?
Move the stage up and down
What does the fine adjustment knob do on a light microscope?
Adjust the focus
What is differentiation?
The process in which a cell becomes specialised
When does most differentiation occur?
When an organism develops
When do plants lose the ability to specialise?
Never
What is the purpose of differentiating cells in mature animals?
For repairing and replacing cells
What is the function of a sperm cell?
To get male DNA to the female DNA
How is the sperm cell specialised for its function?
Long tail, streamlined, lots of mitochondria
What is the function of a nerve cell?
To carry electrical signals around the body
How are nerve cells specialised for their function?
They are long and branched
What is the function of a muscle cell?
To contract
How are muscle cells specialised for their function?
They are long and have lots of mitochondria
What is the function of a root hair cell?
To absorb water and minerals from the soil
How are root hair cells specialised for their function?
Big surface area
What is the function of phloem and xylem cells?
They form phloem and xylem tubes that transport food and water around plants
How are phloem cells specialised for their function?
They have very few sub-cellular structures
How are xylem cells specialised for their function?
Hollow in the centre
What are chromosomes?
Coiled up DNA molecules
Where in the cell are chromosomes?
The nucleus
How many chromosomes does a normal body cell have?
46, 23 pairs
How many chromosomes are from the mother and how many are from the father?
23 each
What is mitosis?
When cells divide
What is the end result of mitosis?
Two identical cells
What does the cell have to to do before it divides?
Duplicate its DNA and increase the amount of sub-cellular structures
What happens when the cell actually divides?
The chromosomes are pulled apart, new nucleus membranes form around each half, then cytoplasm and cell membrane divide
What type of cells divide by binary fission?
Prokaryotic
What happens in binary fission?
DNA and plasmids replicate, cells expands, DNA separate, new cell walls for, cell membrane divides
How many copies of the DNA strands does each new daughter cell have after binary fission?
One
How many plasmids does each daughter cell have after binary fission?
A variable number
What do bacteria need to divide?
The correct conditions
What is mean division time?
The average amount of time a bacterial cell takes to divide
How do you calculate the number of cells produced in a period of time?
Total time the bacteria are producing cells/mean division time = number of divisions.
2 to the power of the number of divisions = number of cells produced
What is another name for undifferentiated cells?
Stem cells
Where can stem cells be found?
Embryos or adult bone marrow
How many types of cell can embryonic stem cells differentiate into?
Any
How many types of cells can adult stem cells differentiate into?
Only a few specific types, such as blood cells
What can stem cells do for medicine?
Cure disease
What type of cells might be replaced by stem cells?
Faulty blood cells, insulin producing cells for diabetics, nerve cells for people who are paralysed
How can rejection be avoided in the use of stem cells?
Therapeutic cloning, giving an embryo the same genes as the patient
Why are some people against stem cell research?
They feel embryos shouldn’t be experimented on as they are potential human lives
Why are some people for stem cell research?
They believe the suffering patient is more important than the rights of embryos
Where are plant stem cells found?
In the meristems
What can plant stem cells be used for?
Cloning a plant
Why is cloning a plant useful?
Can stop rare species being wiped out
What is diffusion?
The spreading out of particles from a high to a low concentration
Where can diffusion occur?
Solutions and gases
What is the concentration gradient?
The difference in concentration
The bigger the concentration gradient…
The faster the rate of diffusion
What else can increase the rate of diffusion?
High temperatures, make particles move quicker
How do substances move in and out of the cell?
Diffusion through the cell membrane
What type of molecules can diffuse through the cell membrane?
Small ones
What is osmosis?
Diffusion of water particles through a partially permeable membrane
What is active transport?
When substances move from a low to a high concentration, against the concentration gradient
What type of cell do we mainly associate with active transport?
Root hair cell
Why does active transport happen in root hair cells?
Because the plant needs the mineral ions from the soil but it often already has a higher concentration of them than the soil does
What does active transport require?
Energy
What is an exchange surface?
The surface has adapted to allow for easier diffusion
What are some properties of exchange surfaces?
Thing membranes, large surface areas, blood supply, ventilated
What are alveoli?
Little air sacs where gas exchange takes place
What diffuses out of the alveoli?
Oxygen
What diffuses into the alveoli?
Carbon dioxide
What are the three main properties of alveoli that maximise diffusion?
Enormous surface area, thin walls, good blood supply
What does the small intestine have to aid diffusion of digested food into the blood?
Villi
What are three main properties of the villi that maximise diffusion?
Large surface area, incredibly thin walls, good blood supply
What do leaves have to allow carbon dioxide, water vapour and oxygen to diffuse in and out?
Holes on the underneath called stomata
What are the stomata controlled by and why?
Guard cells, to prevent water being lost quicker than it is being replaced
What do fish have that allow carbon dioxide and water to diffuse in and out of their bloodstreams?
Gills
What do gills have that create a large surface area?
Gill filaments and lamellae
