B2.1 Supplying the cell Flashcards
What is diffusion?
the net movement of molecules from an area of higher to lower concentration down a concentration gradient
concentration gradient - steeper
the steeper the gradient (i.e. the bigger the difference in concentration) the faster the particles will flow
Which would have a faster diffusion rate - higher or lower temperature? And why?
A higher temp as the particles have more KE, therefore move around more, and collide more frequently
Which would have a faster diffusion rate - Bigger or smaller concentration difference? And why?
The steeper the concentration gradient the higher the rate of diffusion - the more concentrated the particles are in the OG area, the quicker they will spread into e less concentrated area
Which would have a faster diffusion rate - large or small membrane surface area
Larger SA, particles have more chance of colliding with it, the more the particles collide with the membrane, the higher chance they have of diffusing through it
Is osmosis a passive or active process?
Passive - doesn’t require energy
What is osmosis?
The diffusion of water molecules from a dilute solution (high water potential) to a more concentrated solution (low water potential) across a selectively permeable membrane - water moves down the concentration gradient
Does a dilute solution have a high or low water potential? And why?
High, as there are a large number of water molecules
What does the term concentration apply to?
Solute molecules - not water
Does a concentrated solution have a high or low water potential? And why?
Low, as there are few water molecules
Why do animals need to keep the concentration of body fluids inside and outside the cell the same?
There is a larger NO of water molecules out the cell than in, so water diffuses into cell by osmosis, cell swells & eventually will burst
How do fresh water fish take in water?
By osmosis through gills (have thin membrane) as the blood is more concentrated than surrounding water
What is the osmotic effect of a sea water fish?
Sea water = more concentrated than fish blood - loses water by osmosis through gills -fish drinks sea water & gills expel excess salt from blood - keeping its concentration constant
Explain how plant cells become turgid
- If there is water outside cell, it will move into vacuole by osmosis, vacuole will expand, pushing the cytoplasm outwards against cell wall
- cellulose cells all cannot stretch, so vacuole cant continue to expand,pressure of vacuole against cell wall makes cell v. firm - turgid
In a plant cell, is the cell membrane partially or fully permeable?
Partially permeable
In a plant cell, is the cell wall partially or full permeable?
Freely permeable to water
What do cytoplasm and vacuole (cell sap) contain?
A solution of salts and sugars
What happens if the concentration of cell spa is greater in one cell than the cell next to it?
Water will pass by osmosis from the less concentrated to the more concentrated
What happens when cells are short of water?
Tissue is limp and plant is wilting
What happen if cells have taken up enough water by osmosis??
Cells are turgid and tissue is firm
Potato chip practical - method - first 3 steps
- Place 6 boiling tubes in rack - label them A, B, C, D, E, F
- To boiling tubes add the following:
- A - 20cm3 distilled water
- B - 0.25 mol/dm3 glucose solution
- C - 0.50 mol/dm3 glucose solution
- D - 0.75 mol/dm3 glucose solution
- E - 1.00 mol/dm3 glucose solution
- F - 1.25 mol/dm3 glucose solution - Using a cork borer, cut 6 cylinders from a potato, each abt 4cm long
Potato chip practical - method - steps 4 -7
- Using scalpel, trim cylinders so they’re equal length - also remove any potato skin
- Using the balance - measure & record mass of each potato cylinder
- Place a potato cylinder in each BT - make sure u know mass of each potato in the BT
- Leave experiment it run for abt 24 hours
Give 2 examples of passive transport
Diffusion and osmosis
Why does neither diffusion or osmosis require energy?
As molecules are moving down a concentration gradient
What is active transport?
- Movement of ions in or out of a cell through cell membrane
- low to high concentration against concentration gradient
- using energy released during respiration
Give an example of active transport
- Digestion - small intestine carbs broken down into glucose
- glucose actively transported into bloodstream through the villi
- blood takes glucose to the places in body that need it
What are carrier proteins?
- Special proteins that stretch across the width of cell membrane
- particular molecule that cell requires binds to specific carrier protein
- energy is transferred from an energy store to protein so it can change shape / rotate - carrier protein transports molecule into cell
What is mitosis?
Process where body cells divide
- each cell produces 2 identical daughter cells
- these are genetically identical to parent cells
What does mitosis do?
Increases the number of cells in a multicellular organism
What is the process of cell growth and division called?
Cell cycle
What are the 4 stages of the cell cycle?
- DNA replication
- movement of chromosomes
- cytokinesis
- growth of daughter cell
How is DNA replicated?
- DNA molecule unzips forming 2 separate strands
- DNA bases on each strand are exposed
- free nucleotides in nucleus line up against each strand following rule of complimentary base pairs (AT & GC)
- this forms base pairs
- when the whole strand is complete, there are 2 identical molecules of DNA
How do chromosomes move?
- chromosomes line up across centre of cell
- the 2 identical copies of each chromosome, formed when DNA replicated, separate and move to opposite ends of cell
- each end now contains a full set of identical chromosomes
- 2 new nuclei then form
What are nucleotides?
The structural components / building blocks of DNA and RNA
- contains a base (A, T, G, or C), sugar molecule and phosphoric acid molecule
What happens when cells differentiate?
They become specialised to perform a particular job - its structure changes so that it is better adapted to perform its function
Sperm cell adaptations
- flagellum - propels sperm to ovum
- lots of mitochondria - respiration occurs in mitochondria- reactions of recalibration transfer energy from chemical stores to the flagellum
what are fat cells specialised to do?
- to store fat - can be used as a store of energy, helps animal survive when food is short
- insulation - forms protective layer around some organs (heart)
give one adaptation of fat cells
- small layer of cytoplasm surrounding a fat reservoir - can extend up to 1000 x OG size when filled with fat
what are the three main adaptations of a red blood cell?
- biconcave discs - increases SA:V ratio - speeds up diffusion of O2 into cell and CO2 out of cell
- packed full of haemoglobin - this protein binds to O2 to form oxyhaemoglobin
- no nucleus - space to contain more haemoglobin molecules
what are goblet cells? and what do they do?
produce sticky mucus in the epithelium of many organs
- traps dirt and bacteria
where do you find ciliated cells?
mainly in your airways
what does the cilia do? (ciliated cells)
tiny hairs on top of the cells - sweeps mucus away from lungs to the back of the throat. you then swallow the mucus - any bacteria left is killed in stomach
what are palisade cells specialised for?
carrying out photosynthesis
where are palisade cells found?
- near surface of a leaf - packed full of chloroplasts
- have regular shape - allows close packing in leaf, maximises absorption of sunlight
what is the function of a stem cell?
- they are undifferentiated
- divide by mitosis - forming cells which then differentiate & become specialised
- TMT stem cells can develop into any specialised cell and form any type of tissues & organs
- used by body during development, growth and repair
what are the 2 main types of stem cells in animals?
Embryonic and adult stem cells
what are embryonic stem cells?
- found in embryos
- divide by mitosis to produce all cells needed to make an organism
- ability to differentiate into all cell types
what are adult stem cells?
- found in various body tissue (e.g. brain, bone marrow, skin, liver)
- able to differentiate into some cells, but not as many as embryonic
what are adult stem cells used for?
- repairs body - cells divide & generate many new cells
where are stem cells found in plants?
found in a plants meristem
what is a meristem?
plants continue to grow throughout their life - but only particular parts grow - these parts are called meristems - and include shoot tips
can differentiated plant cells divide?
no as their cell walls are thick and rigid
what are some uses of stem cells?
- treating medical conditions - most research is carried out on embryonic stem cells - taken from 4-5 day old human embryo - embryos usually spare that have been created during IVF but not been implanted into uterus
