B2 Flashcards
What is diffusion
- the net/ passive movement of particles from a region of high to low concentration
Factors increasing the rate of diffusion
- Short diffusion distance
- Steep concentration gradient
- Larger SA: V ratio
- Temperature
What is osmosis
- the diffusion of water/solvent molecules through a partially-permeable membrane following the concentration gradient
- passive movement
What is the concentration of water molecules called?
Water Potential
What is an isotonic solution
A solution that has the same solvent concentration inside and outside the cells
What is a hypotonic solution
A solution that has a higher water potential outside the cell
What is a hypertonic solution
A solution that has a lower water potential outside the cell
What happens when water leaves a PLANT CELL
- first the cell will become flaccid when the water leaves the cell then the cell will become plasmolyzed (the content of the cell collapses away from the cell wall)
- hypertonic solution
What happens when water enters a PLANT CELL
- first the plant cell will become turgid and the cell will have increased pressure
- hypotonic solution
What happens when solvent enters an ANIMAL CELL
- the solvent will fill up with water and then get too full and lyse (burst)
What happens when a solvent leaves an ANIMAL CELL
- solvent will leave the cell and the cell will have too little water
- The cell will crenate/crinkle
- hypertonic solution
What is Active Transport?
- the active movement of particles from low to high concentration using energy from respiration
How is active transport carried out?
- the molecules go against the concentration gradient
- carrier proteins in the cell membrane bind to a specific molecule
- They then use energy from ATP to turn and place the molecule in the cell then turn back and repeat the process
What is a carrier protein
- a protein in the cell membrane of a cell that binds to a specific molecule
- They use ATP from respiration to turn
Adaptations of cells that take part in active transport
- many mitochondria as more ATP is needed so more respiration will be done
Place where active transport takes place (plant)
- In the root hair cells
- Use active transport for mineral ions such as nitrates
- They use carrier proteins to get the nitrates for the leaves into the plant
Place where active transport takes place (animal)
- In the small intestine
- carbs are broken down into glucose
- half is diffused into the bloodstream, then concentration gradient is too steep for diffusion
- The other half is absorbed into blood via active transport
What is cell differentiation?
When cells differentiate they specilaise to perform a specififc function
Adaptations of Sperm Cell
- function of a sperm cell is to transfer genetic material from the male to the egg
- Flagellum - tail used for swimmining and propelling the sperm forward
- Lots of mitochondria because lots of energy is used in moving the sperm cell
- Acrosome, stores digestive enzymes which break down the outer layer of the egg cell
Adaptations of a Red Blood Cell
- No nucleus to carry more haemoglobin cells so more oxygen can be carried
- packed full of haemoglobin so most amount of oxygen can be carried
- Is in the shape of a bioconcave disk which increases SA”V ratio speeding up diffusion for carbon dixiode and oxygen
Adaptations of Palisade Cells
- specialised to carry out photosynthesis
- Found near leaf and are packed with chloroplasts
- Regular shaping to allow close packing within leaf maxinimsing absorption of sunlight
What is a stem cell
- A stem cell is an undifferentiated cell that can divide to produce a range of cell types
Where are embryonic stem cells found
- Embryonic stem cells are found in blastocysts which are one step after embryos
- They are totipotent and better than adult stem cells
Where are adult stem cells found
- Mainly found in the bone marrow
- can differentiate into less cells than embryonic stem cells
- Adult stem cells act as repair mechandism for the body
Advantages and Disadvatages of Animal Stem Cells
- Embryonic stem cells can be used for a wider variety of uses
- They are destroyed anyway so may as well be used
- However they cannot give consent
- They also have a right to life
Why does mitosis occur?
- to replace worn out cells
- to repair damaged tissue
- so the organism can increase in size/grow
What is the cell cycle
- The series of stages in the life cycle of a cell
What happens in mitosis
- all the chromosomes in the nucleus are duplicated (DNA replication, outside of mitosis)
- The nucleus is taken away
- The chromosomes line up in the middle of the cell
- The chromosomes’ identical pairs are pulled apart from each other
- 2 New nuclei are formed and the cytoplasm divides and new cell membranes are formed
- There are now 2 identical daughter cells formed
What is the circulatory system made of?
Blood, heart and blood vessels
What is the purpose of a Red Blood Cell?
- to carry oxygen in the blood to the places that require it
- Has a biconcave shape so SA:V increases and oxygen diffuses faster
- Carries Haemoglobin which binds with oxygen to form oxyhaemoglobin
- Has no nucleus to carry more blood
What is the purpose of a white blood cell?
- defend against pathogens
- sometimes by engulfing them
- includes antitoxins and antibodies
What do platelets do?
- cell fragments that help with blood clotting at the site of wounds
What does plasma do?
Plasma carries:
- urea
- blood cells
- hormones
- CO2
- amino acids
- glucose
- It is a pale straw coloured liquid
Where do veins bring blood?
INTO THE HEART
Where do arteries take blood
AWAY FROM THE HEART
What are vessels associated with the lungs called?
Pulmonary
Properties of Arteries:
- Small Lumen - keeps pressure high as blood needs to go to the whole body
- Elastic Fibres and smooth muscle to maintain pressure
Properties of Veins
- Wider lumen
- pressure not needed
- As there is less pressure blood may fall backwards so veins have many valves
- Thinner fibres and muscle
- Veins may also go between muscles to help with lack of pressure
Properties of Capillaries?
- one cell thick wall of cells
- used for gas exchange
- Only 1 red blood cell through at a time
Which blood vessel brings deoxygenated blood from the body and muscles to the heart
VENA CAVA
Which blood vessel brings deoxygenated blood from the heart to the lungs
PULMONARY ARTERY
Which blood vessel brings oxygenated blood from the lungs to the heart
PULMONARY VEIN
Which blood vessel brings oxygenated blood from the heart to all around the body
AORTA
WHat stops blood from backflowing?
VALVES
Why is the human circulatory system a double circulatory system?
Because blood flows to the heart twice each times it goes round the body
What is the upper and lower part of the leaf covered in?
Epidermal Cells
Features of the upper epidermis
- transparent to allow sunlight through
- waterproof
- secretes a layer called the waxy cuticle which is waterproof
Features of the lower epidermis
- Full of holes called stomata which can open and close due to guard cells
Where does photosynthesis occur in a leaf?
Mesophyll
Which cells in the leaf have the most number of chloroplasts?
Palisade cells in the mesophyll
What does a vascular bundle in the root look like?
- Xylem as a cross in the middle, with phloem in the gaps
- So root can still move
What does a vascular bundle in the stem look like?
- Looks like the inside of a lemon with seeds
- Phloem on the outside
- Provides support for the stem
What is the xylem made of?
- Dead cells strengthened by lignin
What is the phloem made off
- living cells, with cell walls in between that act as sieves
What travels through the phloem
- the phloem transports sugars in all directions called TRANSLOCATION
- This is because glucose and starch is needed everywhere
Why is there air gaps in the spongy mesophyll?
- For the efficient diffusion of gases that are required for photosynthesis
What is Transpiration?
- The loss of water vapour from the stomata in the leaves of the plants via evaporation and diffusion
What does the xylem carry?
- Water and minerals ONLY UP THE PLANT
Path of Water through a plant?
- From the root hair cells up the root through the xylem to the leaf, used in photosynthesis
- HOWEVER sometimes the water can use the suns energy and evaporate out of the stomata
What apparatus do we use to investigate transpiration?
POTOMETER
Factors affecting rate of transpiration?
- Light Intensity - means more photosynthesis so more CO2 is needed, so stomata open more so TRSP increases
- Temperature - Means more water evaporates and can escape the stomata when the temperature is higher
- Humidity - Higher Concentration of water in the air outside the leaf, so water will not defy the concentration gradient, decreasing TRSP
- Wind Speed - When water leaves the cell by TRSP then it will get blown away faster resetting concentration gradient once more so rate of TRSP will increase with wind speed
- Surface Area - More surface area means more stomata so more diffusion/ TRSP of water
MENTION DIFFUSION
What do Guard Cells when rate of transpiration is high?
Guard Cells will flatten and close stomata to reduce water loss
What do Guard Cells do when water level is high
- Will open stomata as will become turgid and bend open
Why are stomata generally found on the underside of the leaf?
- so they are shaded from the sun and therefore less water will evaporate
