B1 Flashcards
What can a light microscope magnify up to?
-About X2000
What can an electron microscope magnify up to?
-About X2000000
What resolving power does a light microscope have?
-About 200nm
nm= nanometre
What resolving power does an electron microscope have?
-About 0.2nm
nm= nanometre
calculating the size of an object equation:
magnification = size of image/ size of real object
or
size of real object = size of image/ magnification
what can an electron microscope be used for?
-viewing thin specimens (tissue sections, molecules)
what can a light microscope be used for?
-viewing living cells (onion cells etc.)
what are the cells features in an animal cell and what are their functions?
nucleus: controls the cell, contains genes (chromosomes)
cytoplasm: liquid gel where most chemical reactions occur
cell membrane: controls what enters and exits cell
mitochondria: where aerobic respiration takes place
ribosomes: makes proteins for cell and is where protein synthesis takes place
what are the extra cells features in a plant cell and what are their functions?
cellulose, cell wall: strengthens the cells and gives it support
vacuole: filled with cell sap. keeps cell rigid to support plant
chloroplasts: contain chlorophyll which absorb light for photosynthesis
what are the main structure you would expect to find in a human cell?
- nucleus
- cytoplasm
- cell membrane
- mitochondria
- ribosomes
what extra features are found in plant cell but not animal cells?
- vacuole
- cell wall
- chloroplasts
why are the nucleus and mitochondria so important?
- the mitochondria is where aerobic respiration takes place
- the nucleus controls the cell
What do all eukaryotic cells have?
- cell membrane
- cytoplasm
- genetic material in a nucleus
what do prokaryotes (bacterial cells) consist of?
- cytoplasm
- cell membrane
- cell wall
- genetic material not in a nucleus
- plasmids: extra small rings of dna
- slime capsule: extra protection
- flagella: to move
- ribosomes
- pili: hair-like structure allow bacterial cells to stick to other surfaces
what can happen to an animal organism as it develops?
-cells can differentiate to form idfferent types of cells such as nerve cells, muscle cells, sperm cells etc.
how are nerve cells adapted?
- lots of dendrites to make connections to other nerve cells
- axon carries nerve impulse for one place to another
- synapse (nerve ending) adapted to pass impulses to another cell
how are muscle cells adapted?
- contain special proteins that slide over each other making fibres contract
- contain mitochondria to transfer energy needed for chemical reactions that occur as cells contract
- store glycogen that can be broken down and used for aerobic respiration
how are sperm cells adapted?
- long tails whips to help move sperm
- middle section full of mitochondria which transfer energy needed for tail to work
- acrosome stores digestive enzymes for breaking down outer layers of the egg
- large nucleus contains genetic info to be passed on
how are root hair cells adapted?
- increased surgace area for water to move into the cell
- vacuole speeds up movement of water by osmosis
- mitochondria transfer energy for active transport of mineral ions into root hair cells
how are phloem cells adapted?
-cell walls break down to form sieve plates which allow water carrying dissolved food to move up + down tubes
how are xylem cells adapted?
- cells die + form long hollow tubes to carry water + mineral ions from one end of plant to the other
- spirals and lignin help them withstand pressure of water moving up plant
how are photosynthetic cells adapted?
- chloroplasts contain chlorophyll that trap light for photosynthesis
- continuous layers in leaves and outer layers of stem so they absorb most light
- vacuole helps keep leaf spread out to get most sunlight
what is the function of root hair cells?
-to absorb minerals and water from soil
what is the function of photosynthetic cells?
-plants can make their own food
what is the function of xylem cells?
- to support the plant
- to carry water and mineral ions from roots to the highest leaves and shoots
what is the function of phloem cells?
-carries food made by photosynthesis around the plant
what is diffusion?
the spreading out of particles of any substance, in solution or gas, resulting in a net movement from a high concentration to an area of low concentration, down a concentration gradient
why does diffusion take place faster when there is an increase in temperature?
-the particles in a gas or solution move around more quickly (speed up) so diffusion takes place more rapidly
what affects the rate of diffusion?
- the difference in concentrations
- the temperature
- the available surface area
what is a concentration gradient?
the difference between two areas of concentration
define net movement:
net movement = particles moving in - particles moving out
what is osmosis?
- a special type of diffusion
- the movement of water from a dilute to a more concentrated solution through a partially permeable membranethat allows water to pass through
what is the difference between osmosis and diffusion?
- osmosis occurs across a partially permiable membrane while diffusion does not
- osmosis in organisms also only refers to the diffusion of water molecules
what is a partially permeable membrane?
-membranes that only let some types of particles through
in osmosis what is a dilute solution of sugar?
contains a high concentration of water and has a low concentration of sugar
in osmosis what is a concentrated solution of sugar?
-contains a relatively low concentration of water and a high concentration of sugar
what is an isotonic solution?
-when the concentration of solutes in the solution outside the cell is the same as the internal concentration
what is a hypotonic solution?
-when the concentration of solutes in the solution outside the cell is lower than the internal concentration
what is a hypertonic solution?
-when the concentration of solutes in the solution outside the cell is higher than the internal concentration
what is a solute?
- the minor component in a solution
- dissolved in the solvent
what is a solvent?
-the liquid in which a solute is dissolved to form a solution
what do differences in the concentration of solutions inside and outside a cell do?
-cause water to move into or out of the cell by osmosis
how can osmosis cause big problems in animals?
- if solution outside the cell becomes much more dilute than the cell contents water will move in by osmosis + the cell will swell + may burst
- if solution outside the cell becomes much more concentrated than the cell contents, water will move out of the cell by osmosis + the cytoplasm will become to concentrated + the cell will shrivel up + die
why is osmosis so important in plants cells?
- to maintain turger (hard and rigid) which keeps the leaves and stem of the plant firm
- its the way the plants get water through its leaves and root hair cells
how does active transport work in a cell?
-active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient)
where does active transport get its energy for use from?
-active transport uses energy released from food in respiration to provide the energy required
why is active transport important?
- it allows plant root hairs to absorb mineral ions required for healthy growth from very dilute solutions in soil against a concentration gradient
- it enables sugar molecules used for cell respiration to be absorbed from lower concentrations in the gut into the blood where concentration of sugar is higher
