B2.1 - Supplying the cell Flashcards
What is diffusion?
the (net)/overall movement of particles from a region of high concentration to a low concentration
How do particles move during diffusion?
down a concentration gradient
When does diffusion stop?
when the concentration gradient reaches zero, and the concentration of the particles is the same everywhere
Is energy required during diffusion? and why?
- No, it is a passive process (passive transport)
- it is the ordinary motion of particles
where does diffusion occur in the body? (3)
- diffusion of oxygen and glucose from alveoli to bloodstream
- carbon dioxide diffusing away from respiring cells
During most cases of diffusion, where does it pass through?
the cell membrane
what 3 factors affect the rate of diffusion?
- surface area
- concentration gradient
- distance for diffusion
how do you increase the rate of diffusion?
- increase surface area (more space for diffusion)
- increase concentration gradient (greater net movement of particles)
- reduce distance (less time to travel short distance)
Describe one way blood capillaries have adapted to be most efficient at diffusion
- only one cell thick (increases diffusion gases into and out of bloodstream)
describe one way plant cells have adapted to increase its rate of carbon dioxide diffusion (ie. to get in plant)
- carbon dioxide concentration inside cells drops
diffusion from high -> low
describe one way the small intestine has adapted to increase its rate of diffusion
- wall is highly folded (increase surface area in contact with bloodstream)
Define osmosis
the net movement of water particles across a partially permeable membrane from a region of high water potential to a region of low water potential
What happens when a solute dissolves in water (ie. sugar)?
water molecules cluster around it
define water potential
the concentration of free water molecules
if a solution is concentrated, how does it affect the water potential?
decreases the water potential (less free water molecules)
describe what would happen to a plant cell when its surroundings are a less concentrated solution (higher water potential) than itself
- The free water molecules would diffuse into the cell (through the semi-permeable membrane)
- the turgor pressure would increase
- the cell would become TURGID and firm
describe what would happen to a plant cell when its surroundings are a higher concentrated solution than its cell
- the water molecules would travel out of the cell (through the semi-permeable membrane)
- lose water
- the turgor pressure falls
- the cell becomes flaccid (soft)
- eventually cell contents would collapse away from cell wall
- cell becomes PLASMOLYSED
Define a semi-permeable membrane
a membrane which only allows certain substances to pass through
Also called semi-permeable. A partially permeable membrane allows water and other small molecules to pass through, but not larger molecules such as starch.
describe what would happen to an animal cell when its surroundings have a higher concentrated solution than it
- loses water by osmosis
- becomes CRENATED (crinkled/shrinks)
describe what would happen to an animal cell when its surroundings are a lower concentrated solution than the cell
- water goes into cell
- swells and may burst (no cell wall)
- LYSIS
why is glucose unable to enter a partially permeable membrane?
because it only allows certain substances to pass through, in this case water
define active transport
the movement of molecules against their concentration gradient
in terms of concentration gradients, which way does active transport occur?
low concentration gradient -> high concentration gradient
is energy required for active transport? and why?
- yes, in the form of ATP,
- since particles against the concentration gradient
is energy required for osmosis? why?
no, moves with ordinary motion of particles
state the three features of active transport;
- carrier proteins
- ATP is required (from respiration)
- transported/ pumped against concentration gradient
what process makes ATP?
respiration
do cells that carry out a lot of active transport have a lot of mitochondria? why?
- yes
- so that they can respire rapidly to produce large quantities of ATP
what affects the rate of active transport?
- rate of ATP produced during respiration
State where carrier proteins are found in cells
- across the width of the cell membrane
describe the process of of active transport (with carrier proteins etc.)
1) energy is transferred from an energy store to the carrier protein
2) carrier protein binds with specific molecule (active site)
3) protein either changed shape or rotates
4) molecule is transported into cell
when is active transport used?
- whenever a substance needs to be transported against the concentration gradient
describe 2 examples where active transport is used in animals
1) digestion -
carbohydrate broken down to glucose in small intestine
glucose actively transported through vili into bloodstream
2) nerve cells-
carrier protein pumps sodium ions out of cell
potassium ions are pumped back in (the sodium potassium pump plays an important role in creating nerve impulses)
describe an example where active transport is used in plant cells
- what ions are needed to form proteins?
- specifically where is it used (ie. what surface)
- take minerals from soil
- plants need nitrate ions for proteins
- use active transport to move ions across cell membrane into root cell
state two difference between active transport and diffusion
- active transport uses ATP, diffusion does not
- active transport moves against concentration gradient, diffusion moves along concentration gradient
State the purpose of mitosis
- to replace worn out cells
- to repair damaged tissue
- (increases number of cells in a multicellular organism)
- enable the organisation to increase in size
what is mitosis the process of?
by which body cells divide
what do cells divide to during mitosis?
- two daughter cells (with identical DNA)
- clones
why must mitosis occur constantly?
since we constantly lose cells from the surface of your skin
what are the 4 stages of the cell cycle?
1) DNA replication
2) movement of chromosomes
3) Cytokinesis
4) the growth of the daughter cell
Describe the first stage of the cell cycle
DNA is replicated :
1) DNA molecule unzips
2) DNA bases on both strands are exposed
3) free nucleotides in the nucleus line up against each of the strands following the rule of complementary base pairings
4) this forms DNA base pairs
5) When whole strand is complete = two new identical molecules of DNA
Describe the second stage of the cell cycle;
Movement of chromosomes:
- chromosomes line up across center of cell
- chromosome separates and moves to opposite ends of cell
- each end has full set of chromosomes
- nuclei form (nuclear membrane forms)
Describe the third stage of the cell cycle:
Cytokinesis
1) cell membrane pinches inward to separate
2) enclosed two new nuclei
3) cell membrane pinches off to split original cell to two new genetically identical daughter cells
what happens when cells differentiate?
- they become specialised to perform a particular job
what happens when a cell becomes specialised?
- structure changes so that it’s adapted to perform its function
- entire organism becomes efficient
how is a sperm cell specialised?
- to transfer genetic material from male to ovum (egg)
- flagella
(whips side to side to propel cell through liquids) - lots of mitochondria
(high rate of respiration from chemical stores for it to move fast) - acrosome at top of cell
(enzymes which break down outer layers of ovum to allow sperm to transfer energy and incorporate genetic material)
how are fat cells adapted to their role?
- small layer of cytoplasms around fat reservoir in cell
- can expand up to x1000 original size as filled with fat
how are red blood cells specialised to their role?
TRANSPORT OXYGEN
- biconcave discs (goes in at middle) increase surface area : volume ratio - haemoglobin (protein which allows oxygen to bind to red blood cell) - no nucleus (lots of space to pack in haemoglobin)
Define cell differentiation
conversion of an unspecialised cell to become specialised to perform a particular task efficiently
what can fat cells be used for?
- store of energy
- insulation
- protection around vital organs
what are the function of ciliated cells?
- traps dirt and bacteria in airways
Textbook =
have ciliated cells in your airways. In between these cells are goblet cells, which produce sticky mucus. This traps dirt and bacteria. The cilia (tiny hairs) on the top of the cells sweep the mucus away from your lungs to the back of the throat. You then swallow the mucus. Any bacteria present are killed in your stomach.
how are ciliated cells specialised to their role?
- goblet cells produce sticky mucus
- cilia (hair on top of cells) sweep mucus away
Produces mucus to trap dust mucus and bacteria which the cillia then waft back up the throat to be swallowed.
how are palisade cells specialised to their role (plant)?
- chloroplast found near surface of cell
- packed with chloroplast
- regular shape = close packing within the leaf(maximise absorption of sunlight)
state the function of a palisade cell
- to carry out photosynthesis (same as plant cell)
what are stem cells?
undifferentiated cells
what is a key feature of stem cells?
- they can divide to form any kind of specialised cell
- can form all types of tissues and organs
what are stem cells used by the body for?
- development
- growth
- repair
What are the two main types of stem cells?
- embryonic
- adult
describe features of an embryonic stem cell
- found in embryos
- divide by mitosis
- ability to differentiate into all cell types
describe features of an adult stem cell
- found in various body tissues (brain, bone marrow, skin, liver)
- able to differentiate into some types of cells but not as many as embryonic
What kind of cells does a stem cell in your blood differentiate to?
- white blood cell
- red blood cell
- platelets
what do adult stem cells act as in the body?
- repair mechanisms
which part of plants grow? and what are they?
meristems - include shoot tips
where are stem cells found in plant cells (and what are they called)
at tip (meristems) - but can be found on stem for example as well to make stem thicker (by dividing)
describe features of meristem cells
- small compared to plant cells
- very thin walls
- small vacuoles
- no chloroplast
can differentiated plant cells divide?
no, cell walls are thick and rigid
does oxygen move from lungs into the blood through diffusion or active transport?
diffusion
do carbon dioxide enter leaves of plants through diffusion or active transport?
diffusion
is glucose absorbed during digestion an example of diffusion or active transport?
active transport
why would a potato slice become longer in pure water?
- water enters by osmosis
- cells swell/bloat/become larger
Suggest why cells need to differentiate.
• to do different jobs
State three uses for mitosis in organisms.
- growth/making more cells
- replacing (dead) cells
- repairing tissue/organs
Describe the difference between embryonic and adult stem cells in humans.
- embryonic cells can turn into any type of cells
- adult cell can only turn into certain types
what is concentration a measure of?
how much solute is dissolved in a given volume of solvent
what is urea?
- and what does the body do with it?
the waste product of cells, diffuses from the cells and into the blood to be removed by kidneys
what two substances can be removed during diffusion?
carbon dioxide, urea
can water molecules move both ways during osmosis?
yes, but the net movement is from high w.p to low w.p
what is the equation for percentage change in mass?
((final mass - initial mass) ÷ initial mass) x 100
what is an important role of active transport in plants?
allow root hair cells to absorb mineral ions even through concentration of minerals is lower in soil than roots
why is sugar important in the body?
for cellular respiration
why are mineral ions required in plants?
for healthy growth
what adaptations are used by multi cellular organisms to maximise the efficiency of a gas?
thin membrane, blood supply, large surface area
what is the small intestine adapted for?
exchanging nutrients between digested food in the small intestine and the blood
what is the independent variable?
the variable that is changed throughout the experiment
ie when investigating rate of photosynthesis with different temperatures, temperature is the i.v
How is a nerve cell specialised
- covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse
- has extensions and branches, so that it can communicate with other nerve cells, muscles and glands.
Specialisation table (5) from spec
How does a zygote divide
By mitosis
