B1 - Cell structure and transport Flashcards
How do we observe cells?
Using a microscope.
What is a light microscope?
A microscope that uses visible light and lenses.
What are the key features of a light microscope?
Stage, objective lens, eye piece lens, coarse focus, fine focus, light, slide
What is an electron microscope?
A microscope that uses electrons and electron lenses.
What is magnification?
How many times larger something actually is.
What is resolution?
Minimum distance apart that two objects can be, in order for them to be seen as separate objects.
What are the advantages of using an electron microscope compared to a light microscope?
Higher magnification and resolution.
How is magnification calculated?
magnification = image size / actual size
What does the prefix milli mean?
Thousandth of a metre
What does the prefix micro mean?
Millionth of a metre.
What does the prefix nano mean?
Billionth of a metre.
What is the relationship between these prefixes?
1000x smaller each time.
What is the function of the nucleus?
Contains genetic material (DNA) which controls the cells activities.
What is the function of the cytoplasm?
Jelly-like substance where most chemical reactions take place.
What is the function of the cell membrane?
Surrounds the cell and controls movement in and out of the cell.
What is the function of mitochondria?
Part of the cell where energy is released from glucose.
What is the function of the ribosome?
Where protein synthesis takes place.
What is the function of the cell wall?
Provides structure and support.
What is the cell wall made of?
Cellulose.
What is the function of the chloroplast?
Where photosynthesis takes place.
What substance is contained in the chloroplasts that absorbs light?
A green pigment called chlorophyll.
What is the function of the vacuole?
Contains cell sap, a solution of sugar and salts.
What is the structure of eukaryotic cells?
Have a cell membrane, cytoplasm and genetic material that’s enclosed in a nucleus.
What type of organisms contain eukaryotic cells?
Animal and plant cells.
What is the structure of prokaryotic cells?
Contains cytoplasm, cell membrane, cell wall, rings of DNA called plasmids but genetic material is NOT enclosed in a nucleus.
What type of organisms contain prokaryotic cells?
Bacteria
What is a sub-cellular structure?
Structures within the cell.
What sub-cellular structures do animals cells have?
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.
What additional sub-cellular structures do plants have that animal cells don’t?
Cell wall, chloroplasts, permanent vacuole.
What is differentiation?
The process by which a cell changes to become specialised for a particular job.
When does most cell differentiation happen in animals?
At an early stage of development (as a foetus).
What is cell division mainly used for in mature animals?
To repair and replace cells.
When does cell differentiation occur in plants?
Most plant cells retain the ability to differentiate throughout the life of a plant .
What is a specialised cell?
A cell that has a structural adaption to perform a particular function.
What are 3 examples of specialised cells in animals?
Sperm cells, nerve cells and muscle cells.
How is a sperm cell specialised to carry out its function?
Long tail and streamlined head to swim; lots of mitochondria to provide it with energy.
How is a nerve cell specialised to carry out its function?
They’re very long with branched connections to connect to other nerve cells and form a network in the body.
What are 3 examples of specialised cells in plants?
Root hair cells, xylem and phloem cells.
How do bacteria divide? (Triple only)
By binary fission
How often can bacteria divide through binary fission? (Triple only)
Up to once every 20 minutes
How are bacteria grown in a lab? (Triple only)
On a nutrient broth solution or as colonies on an agar gel plate
What is the definition of ‘aseptic’? (Triple only)
‘Free from contamination’
Why is it important we can grow uncontaminated cultures of microorganisms? (Triple only)
To investigate the action of disinfectants and antibiotics
What steps are taken when preparing an uncontaminated culture using aseptic technique? (Triple only)
STEP 1: Petri dishes and culture media must be sterilised before use
STEP 2: Inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame
STEP 3: The lid of the Petri dish should be secured with adhesive tape and stored upside down
Why is it important equipment is sterilised before and during aseptic technique? (Triple only)
To prevent contamination of unwanted microorganisms
Why is the lid of the petri dish secured with adhesive tape? (Triple only)
To prevent microorganisms entering or leaving the petri dish
Why are petri dishes stored upside down? (Triple only)
At what temperature should bacterial cultures be
To stop condensation dripping on the agar
At what temperature should bacterial cultures be stored in school laboratories? (Triple only)
25°C
Why do schools use a maximum temperature of 25°C when incubating cultures? (Triple only)
To avoid harmful bacteria growing
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration.
What do particles do during diffusion?
Spread out until their concentration is even.
What factors affect the rate of diffusion?
Temperature, concentration gradient, the surface area of the membrane.
What substances diffuse in/out of cells?
Oxygen and carbon dioxide in gas exchange.
Glucose, amino acids, fatty acids, and glycerol in digestion.
Water in the large intestine.
Urea in the kidney.
What is osmosis?
Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
Why is osmosis important in plants?
To maintain turgor in plant cells.
What is active transport?
Active transport moves substances from a more dilute solution to a more concentrated solution which requires energy from respiration.
Where and how does active transport take place in plants?
Root hairs; mineral ions are absorbed into the root hair cells from very dilute solution in the soil.
Why do plants require ions?
For healthy growth.
Where does active transport take place in animals?
Sugar molecules are absorbed from lower concentrations in the gut to higher concentrations into the blood in the small intestine.
What are sugar molecules used for?
Respiration
How does surface area to volume ratio relate to the size of an organism?
The smaller the organism, the larger its surface area to volume ration.
What affect does surface area to volume ratio have on an organisms ability to exchange substances with its surroundings?
Single celled organisms have a large enough surface area compared to its volume to absorb substances it needs from the environment.
Multicellular organisms need specialist surfaces and organ systems to be able to exchange substances with the environment.
What are the features of a good exchange surface?
Large surface area.
Good blood supply to maintain a big concentration gradient.
Thin, to provide a short diffusion path.
What are two specialist exchange surfaces in mammals?
Villi in the small intestine and alveoli in the lungs.
What specialist exchange surface does a fish have to exchange?
Gills.
