topic 4 Flashcards
Why is transport needed in cells?
- cells require supply of chemicals (glucose + oxygen for cellular respiration = must be transported from outside the organism into the cell.
- waste products such as CO2 must be transported out of the cell before it causes damage.
- cells need to transport substances made in one area to another or out of cell completely
The fluid mosaic model of the cell membrane
cell surface membrane controls transport of materials in/out of cells
- Fluid - phospholipid molecules can move around within each layer freely = membrane is flexible and can change shape.
- Mosaic - protein molecules are scattered around the membrane
Phospholipid bilayer with hydrophobic polar tails facing inwards on themselves and hydrophilic heads facing out.
Glycoproteins ( proteins with carbohydrate added)
- act as antigens on outer surface acting as receptors and important for cell recognition
Integral proteins
- can form pores / channels = allow specific molecules to move through (gated channels open + shut depending on conditions of cell) or simple gaps in lipid bilayer that allow ionic substances to move through in both direction
Peripheral proteins (can be enzymes)
- Form temporary bonds with the cell membrane, allowing them to detach + reattach at specific times - involved in regulating transport by eg cell signalling.
2 Main types of transport in cells?
Passive transport - involves no energy from cell, takes place due to concentration / pressure
Active transport - involves moving substances in or out cell up a conc gradient using ATP produced from cellular respiration.
3 Passive transport mechanisms?
-
Diffusion - movement of particles in liquid/gas down a concentration gradient from area of high conc to low conc as a result of random movements, until they reach a uniform distribution.
[after that equal numbers of particles move in all directions= doesn’t change conc]
- the phospholipids in bilayer just simply move apart to allow it pass through - Facilitated diffusion - diffusion that takes place through carrier proteins or protein channels
-
Osmosis - movement of water molecules down a conc gradient through a partially permeable membrane.
- water passes through channel protein to avoid the hydrophobic centre of phospholipid bilayer
3 Active transport mechanisms
-
Endocytosis - movement of large molecules into cells through vesicle formations.
[cell extensions (pili) engulf material to form a vesicle = which enters the cytoplasm] -
Exocytosis - movement of large molecule out of cells by the fusing of a vesicle containing the molecule with the surface cell membrane.
[Vesicles fuse with cell membrane to release the contents from cell] - Active transport - Movement of substances across membrane of cells directly using ATP (often up a conc gradient)
Facilitated diffusion through gated channels and carrier proteins
which type of substances use this?
- gated channels - open only when a specific molecule is present or there is an electrical change across membrane, and then close afterwards.
- Carrier proteins are specific for particular molecules, depending on the shape of the protein and the substance being carried.
- once the protein carrier of specific shape picks up substance from area of high conc, it changes shape
=allowing the molecules to get passed into the cell/area of low conc
- protein carrier then returns to its original shape - to allow more molecules to enter and then repeat.
it can only work when conc gradient is in the right direction as it does not use ATP (its passive)
Used by charged substances (eg glucose) because the cell membrane repels them.
Factors that affect rate of diffusion?
- surface area ( large SA = higher rate, as more particles can be exchanges at same time due to larger surface available)
- temperature (higher temp = move faster = higher rate)
- concentration (steeper conc gradient = the faster the particles move = higher rate)
- membrane thickness ( the distance they have to travel = shorter diffusion distance/thinner membrane = faster diffusion)
How might certain properties of a molecule affect how it’s transported?
- solubility = lipid-soluble molecules pass through membranes more easily.
- size = smaller molecules diffuse faster
- charge = charged molecules cannot diffuse by simple diffusion as membrane repels them so have to use facilitated
Osmotic concentration
- isotonic solution?
- hypotonic solution?
- hypertonic solution?
Isotonic solution - osmotic concentration of the solutes in the solution is the same as that in the cells
Hypotonic solution - Osmotic concentration of solutes in solution is LOWER than in cytoplasm of cells.
Hypertonic - Osmotic concentration of solutes in solution is HIGHER than in cytoplasm of cells.
Osmosis in :
-animal cells
-plant cells
animal cells:
- too much water moves out = cell shrivels as concentrated cytoplasm loses its internal structure and the chemical reactions stop working
- too much water moves in = cell burst
plant cells:
- too much water moves out = turgor is lost + cell membrane begins to pull away from cell wall as the protoplasm shrinks = called incipient plasmolysis + vacuole will be reduced
- too much water moves in = cytoplasm swells and presses on cell walls = becomes rigid = turgor = this state supports the stems + leaves of plant
[this is because the pressure of cytoplasm on cell wall is cancelled out by the inwards pressure of the cell wall on the cytoplasm (pressure potential) to stop water ]
in plants they do not swell/burst , only the contents change.
- Water potential?
Water potential - measure of the tendency of water to move by osmosis.
-pure water has highest water potential of 0.
-osmosis occurs from high water potential to low.
- Turgor pressure?
Measure of the inwards pressure exerted by the cell wall on the protoplasm of the cell as cell components expand + press outwards
-this force opposes/stops entry of water by osmosis
- turgor pressure has a positive value
- Osmotic potential?
Measure of the potential of a solution to cause water to move into the cell across a partially permeable membrane from high conc to low conc
-pure water has highest (least negative) osmotic potential
-solution with dissolves solute =lower (more negative)
-the greater solute cocn = the more negative
-osmotic potential has a negative charge
How can water potential be calculated?
Water potential = turgor pressure + osmotic potential
ψ = P + π
usually negative = usually positive + always negative
When turgor pressure is balanced with osmotic potential the cell is …
At turgor
How does active transport work
best example of active transport is sodium pump that actively moves potassium ions into cell and sodium ions out.
- Protein carrier of specific shape picks up glucose molecule of specifc shape
- Protein carrier changes shape to allow glucose molecules into the cell -this requires energy from the hydrolysis of ATP into ADP + P
- Glucose molecules are carried across membrane in protein carrier of matching shape from low conc to high conc
- Glucose molecules released and protein carrier returns passively to original shape to allow more glucose molecules to enter.
Explain the role of ATP in active transport
ATP binds to the carrier protein, providing enough energy for the protein to change shape, which carries the molecule in/out of cell.
Hydrolysis of ATP into ADP + P
How does ATP release energy?
When ADP is phosphorylated to form ATP, this requires energy which is then stored in the molecule.
Therefore when ATP is hydrolysed, the energy stored is released to be used were required.
Evidence for active transport using ATP?
- active transport takes place only in living , respiring cells
- The rate of active transport depends on temp + O2 conc. These also affect rate of respiration and so ATP production as well
- Many cells that are known to carry out active transport, have lots of mitochondria -site of aerobic respiration and ATP production
- Poisons that stop respiration or prevent ATPase from working, also stops active transport.
What is SA : V ratio and how does it affect gas exchange?
The relationship between the SA of an organism and its volume.
the larger the SA is compared to Volume =the more particles can be exchanged at same time = faster gas exchange
Gas exchange in small organisms?
why does it work like that?
For single-celled organisms (eg amoeba) nutrients/o2 can diffuse directly into cell from external environment + waste products directly out.
This works because:
- diffusion distance from outside to inside is very small
- SA:V ration is very large = there is big SA = more substances can diffuse in/out
- metabolic demands are low = don’t regulate own temp/ don’t use much o2 and produce much co2 etc = don’t need gas exchange to happen rapidly
= don’t need specialised gas exchange/ transport systems as diffusion is enough to supply their needs.
Gas exchange in larger organisms
Larger organisms made up of billions of cells = substances need to travel long distance from outside to reach cytoplasm of cells.
Metabolic rate is also higher as they control own body temp and are more active = demand for O2 + food and CO2 + waste produced is much higher than smaller organisms.
= have evolved specialised systems to exchange gases they need in and need to remove.
humans - in lungs
fish - in gills
insects - in tracheal system
plants - in leaves
What features make a gas exchange system effective?
- A large SA : V
- thin layers =minimise diffusion distance
- rich blood supply to maintain a steep concentration gradient
- Moist surfaces to allow gases to dissolve in it
- Permeable surfaces = allow free passage of respiratory gases
Nasal cavity in humans
main entrance for gases into the body
-the lining secretes mucus and is covered in hairs = external air is ‘filtered’ from dust /small particles and pathogens such as bacteria breathed in
-rich blood supply raises temp of air if needed
-moist surfaces increase level of water vapour in air
=all means that air entering lungs has little effect on internal environment.
Functions of parts involved in gas exchange in mammals
-Nasal cavity
-mouth
-Epiglottis
-Trachea
Nasal cavity - main route air enters gas exchange system.
Mouth - air can enter but it misses out on the cleaning of the nasal system
Epiglottis - Flap of tissue that closes over glottis when food is swallowed to stop food from entering gas exchange system
Trachea - Airway to bronchi lined with mucus secreting cells and cilia to move mucus / dust / microorganisms away from lungs.
-incomplete rings of cartilage
-left and right bronchus
-Lung
-Bronchioles
-Alveoli
incomplete rings of cartilage - prevent trachea + bronchi from collapsing + allow food to be swallowed and move to oesophagus
Left + Right bronchus - Tubes leading to lungs ( similar to trachea structure but narrower and divide to form bronchioles)
Lung - organ where gas exchange takes place
Bronchioles - small tubes that spread through lungs and end up in alveoli. (no cartilage and collapse easily)
Alveoli - Main site of gas exchange in lungs (tiny air sacs)
-Ribs
-Intercoastal muscles
-pleural membranes
-pleural cavity
-Diaphragm
Ribs - protective bony cage around the gas exchange system
Intercoastal muscles - found between ribs and important in breathing
Pleural membranes - surround the lungs and + line the chest cavity
Pleural cavity - space between the pleural membranes usually filled with lubricating fluid that allows membrane to slide easily with breathing movements
Diaphragm - broad sheet of tissue that forms the floor of chest cavity + important in breathing movements
Alveoli structure w capillaries
- Made of single layer of flattened epithelial cells
- capillaries run close also one cell thick wall
- layer of elastic connective tissue between alveoli + capillaries
- hold everything together and help force air out lungs which are stretched when u breath in = elastic recoil of lungs
- Lung surfactant (phospholipids) coats alveoli - preventing alveoli from collapsing = makes breathing easier
Gas exchange in alveoli
Alveoili has high conc of O2 + blood has high conc of CO2
02 diffuses into deoxygenated blood’s red blood cells and makes it oxygenated where its then carried to rest of body to use.
CO2 diffuses into alveoli and is then breathed out.
Adaptations of gas exchange system
(mammals)
- Large SA:V - Many (480-500) alveoli in lungs
- walls of alveoli + capillaries are one cell thick = short diffusion pathway
- Continuous flow of blood in capillaries that maintains conc gradient
- Moist walls for gases to dissolve in
What is Breathing / ventilation?
The process in which physical movements of the chest change the pressure so that air is moved in or out.
Process of inhalation ?
inhalation - taking air into the chest
[active, energy-using process]
-muscles around diaphragm contract = lowered + flattened
-intercostal muscles between ribs contracts = raising rib cage upwards + outwards
Process of inhalation ?
inhalation - taking air into the chest
[active, energy-using process]
-muscles around diaphragm contract = lowered + flattened
-intercostal muscles between ribs contracts = raising rib cage upwards + outwards
= volume pf chest cavity increases
=reduces pressure in cavity
=pressure within chest < pressure atmospheric air outside
=air moves in through trachea - bronchi - bronchioles - lungs to equalise the pressure inside and out
process of exhalation
Takin air out lungs - breathing air out
[passive process]
-muscles surrounding diaphragm relax
=moves up into resting domed shape
-intercostal muscles relax = ribs move down + in
-volume of chest cavity decreases
=increase in pressure
=pressure inside . pressure outside
=air moves out of lungs through bronchioles - bronchi - trachea - out
How your lungs are protected from pathogens and other harmful particles we may breath in?
-we breath in lots of tiny particles/dust/pollen/smoke particles/pathogens (cause disease)
-respiratory system produces loads of mucus that lines airways + traps these little particles / organisms
-moved up the airway by cilia that sweeps up the back of throat
=mucus swallowed
-acid in stomach + digestive enzymes digest the mucus and what its carrying.
Gas exchange in insects
have high o2 requirement - their respiratory system evolved to deliver o2 directly to the cells and remove co2 same way.
spiracles - along the abdomen of most insect
- They are site of entry/exit of respiratory gases
- Opened/closed by sphincters (these also control water loss)
Tracheae - largest tubes that carry air directly into body for gas exchange with cells
- supported by spirals of chitin - hold the trachea open if they are squished
- Chitin makes trachea impermeable to gases = little gas exchange takes place in these vessels
- Trachea divides to form narrower tubes - tracheoles
Tracheoles - narrow tube - a single elongated cell
- no chitin = freely permeable to gases
- spread through the tissues of insect
- so small = run between and even penetrate into cells
=most gas exchange occurs in tracheoles.
Spiracles and sphincters
-air enters through them
-major site of water loss
-sphincters kept closed as much as possible to prevent water loss
-one or two pairs open occasionally to allow enough air in for gas exchange
-when insects active = more spiracles open due to higher demand for O2
-opening + closing of spiracles coordinated by respiratory centres in nervous system which are stimulated by increase of CO2 or lactic acid build up in active tissue due to lack of O2.
Adaptation in respiratory system
[insects]
air moves along trachea + tracheoles by diffusion alone.
- huge network of tiny tracheoles gives large SA = most gas exchange occurs here
- moist walls = gas dissolve
- tracheoles may contain water towards end = limits penetration of gases for diffusion
-when insect very active + needs more O2 = lactic acid builds up in muscle tissues = these affects osmotic conc of cells = so water moves off tracheoles into cell by osmosis = exposes more SA in tracheoles for gas exchange.
Some insects have very active lifestyles + very high energy demands.
How do they get extra O2 supplied?
[dragonflies/butterflies/moths/bees/wasps/flies]
Have evolved ways of ventilating:
- Mechanical ventilation
- air actively pumped into tracheal system.
- when spiracles open = insects make muscular pumping movements of thorax/abdomen
- changes volume + pressure inside body
=drawing air in + out trachea + tracheoles
- Collapsible tracheae / air sacs that act as air reservoirs
- increase volume of air moved through respiratory system
- the ventilating movements of abdomen/thorax inflate/deflate them or some by general body movement
why would lungs not work as gas exchange organs in fish?
water is a lot dense and thick than air
air is 20% o2 whilst water has a lot less dissolved o2
=lungs - would use up enormous amount energy to move water in and out.
-so gills used instead - water flows over them in 1 direction only
=more effective + efficient in terms of energy for fast moving active animals living in water
Gas exchange in bony fish
have high o2 demand due to high active but cannot gas exchange through their scaly external as its not vry permeable to gases = use gills instead
- gills contained in a gill cavity + covered by a protective bony flap called the operculum
- operculum is important in maintaining flow of water over the gills, even when fish is stationary.
Structure of the gills
- gill filaments (lamellae) occur in large stacks
- gill filaments - main site of gas exchange
- need water to keep them apart = to keep large SA needed
- out of water, gill filaments stick together due to lack of water = exposed SA not enough for effective gas exchange + not enough water + o2 can enter
- have a rich blood supply
- blood leaving gills flows in opposite direction to incoming water
(counter current exchange system)
= steep conc gradient maintained
Process of Ventilating the gills in bony fish that have a o……. ?
-sharks + rays do not have an operculum
=have to swim all the time to keep water flowing in through their mouths + out over their gills.
-bony fish have operculum = can ventilate their gills even when not moving
- The floor of the mouth opens, and the operculum (gill flap) closes.
- The floor of the mouth is then raised to increase the pressure but a valve stops water from leaving.
- The increased pressure forces the operculum open which forces water over the gills.
Adaptations in gas exchange system ?
[ in fish]
- Large SA due to gills ligaments being kept apart by water
- Rich blood supply
- thin walls (short diffusion distance)
-
Countercurrent exchange system - blood in gill filaments flow in different direction than the water moving over the gills
= steep conc gradient maintained - Overlapping gill filaments - tips of adjacent gill filaments overlap = increases resistance to flow of water = slows down the flow of water over gills surface = gives more time for exchange of gases to occur.
Plants respire + photosynthesise and they’re opposite?
how’s it balanced?
- respiration - need O2 + release CO2
- photosynthesis - need CO2 + release O2
-during day photosynthesising tissue (green leaves + stems) need to take in MORE CO2 than is produced in respiration
-they also make MORE O2 than is needed in respiration = release it into air
-at day + night, plants take in 02 and release CO2 in respiration.
Main site of gas exchange is leaves
-different parts of leaf?
- Impermeable waxy cuticle (prevents water loss through evaporation/diffusion of gases)
- Upper epidermis (is transparent to allow maximum light through to cells with chloroplasts)
- Palisade mesophyll layer (cells are stacked vertically to fit in as many cells as possible. These cells contain the most chloroplasts - needed for photosynthesis)
- Spongy mesophyll layer (air spaces provide an increased surface area for gas exchange and allow gases to diffuse)
- Lower epidermis, guard cells, stomata (guard cells open and close stomata to control water loss = entry/exit of gases. Walls of guard cells are thicker on the side adjacent to the stomata to enable opening and closing)
Why is the spongy mesophyll layer important?
The spongy mesophyll cells inside have irregular shapes increasing SA.
-arranged with large air spaces between them
-Surfaces of spongy mesophyll cells are moist = gas exchange occurs freely between cells of the leaf + air spaces by diffusion.
how is a conc gradient maintained?
Gases move in + out leaf, maintaining a conc gradient so that gas exchange continues within the leaf.
the gases move in and out of leaf through diffusion through the stomata
What happens when conditions for photosynthesis are favourable?
During the day, when conditions are favourable for photosynthesis…
the stomata opens (this allows water loss to be balanced).
This allows carbon dioxide to diffuse in and oxygen (as a waste product of photosynthesis) to diffuse out.
Opening of stomata?
-a turgor-driven process
-guard cells respond to lowered CO2 levels in leaf
When CO2 needed in cells for photosynthesis in favourable conditions…
- Ions (mostly potassium) move into the guard cells by active transport
- = causes water to move in by osmosis as water potential is decreased
- = makes the guard cells swell + become turgid
- = causes the stomata to open
(due to the uneven bending due to arrangement of cellulose in cell wall)
Walls of guard cells are thicker + less flexible on the side adjacent to the stomata to enable opening and closing
Closing of stomata?
When conditions are less favourable for photosynthesis / when its dark.
- the active pumping of potassium ions into the cell stops = potassium ions are excreted
=water leaves the cell by osmosis - so turgor is reduced + guard cells become flaccid
=closing the stomata
where are stomata found?
most stomata are found on the underside of leaves
they are also present in stems to allow gas exchange to take place
What happens to the stomata on green stems when plants become thickened + woody?
When plants become thickened + woody, there are no stomata on surface anymore.
tissues underneath layers of cork + bark still need to take up O2 + remove CO2 for respiration, so..
special spongy areas called lenticels develop - which are made of loosely arranged cells with many air spaces.
they link the inner tissues of trunk or woody stem with them outside world so gas exchange can take place.
Lenticels can also form on roots for exchange of gases with the air in soil.
What are Lenticels?
Spongy areas with loosely packed cells that are site of gas exchange in woody stems and roots.
What are mass transport systems?
Why is transport in organisms important/needed?
Mass transport system - substances are transported in the flow of a fluid with a mechanism for moving it around the body
- for delivering O2 + nutrients and removing waste = so cells can carry out function efficiently
- transporting substances made internally around the body to where they are needed.
Features of an effective mass transport system
- A system of vessels that carry substances
- A way of making sure substances are moved in right direction
- A mean of moving material fast enough to supply needs of organism
- A suitable transport medium
Open vs Closed circulatory system
Open circulatory system (fish) :
- blood circulating in large open space.
Closed circulatory system (larger animals-mammals) :
- blood is contained within tubes, and makes a continuous journey out to distant part of body and back to heart.
Single circulation system:
Fish (bony fish)
- heart pumps deoxygenate blood to gills
- gas exchange occurs and it becomes oxygenated (at gills)
- blood travels on around rest of body giving up O2 to body cells
- returns to heart + repeat process
Double circulatory system
Involves 2 circulatory systems.
Systemic circulation :
- carries oxygenated blood from heart to cells where O2 is given used. - carries the now deoxygenated blood back to heart.
Pulmonary circulation :
- carries deoxygenated blood from heart to lungs for gas exchange to become oxygenated. - carries now oxygenated blood back to heart.
Why do birds and mammals need a double circulatory system instead?
- need far more O2 than fish
- maintain a constant body temp that’s usually higher than surrounding
=takes a lot of resources = cells need lots of O2 + glucose + produce lots of waste products that need to be removed quickly
Advantages of a double circulatory system in mammals:
- The separate circuits make sure that oxygenated and deoxygenated blood do not mix.
-so tissues can get as much O2 as possible - The oxygenated blood can be delivered quickly to the body tissues at high pressure.
-at lungs blood go through tiny vessels that allow gas exchange to occur effectively.
-if this oxygenated blood carried on to rest of body at low pressure, it would move very slowly
-as it returns to heart it can be pumped at high pressure around body = reaches all capillaries between body cell quick - supplying O2.
What does it mean that the mass transport system is the cardiovascular system?
What does this system do?
The mass transport system of the body made up of a series of vessels with a pump (the heart) to move blood through the vessels.
- delivers materials needed by cells of body + carries away waste products of their metabolism.
- carries hormones (chemical messages) from one part of body to another
- forming part of the defence system of the body
- distributing heat
main categories of the functions of blood?
The components of the blood?
- transport hormones
- defence
- distribution of heat
- formation of tissue fluid + lymph
Blood is made up of plasma and blood cells (erythrocytes, leukocytes and platelets).
Components:
-plasma
-Erythrocytes (red blood cells)
-Leucocytes (white blood cells)
-Platelets
Plasma
The water solution of your blood carrying other components in it
- Transports digested food products (e.g. glucose, amino acids from small intestine to rest of body)
- nutrient molecules
- hormones
- excretory products (e.g. carbon dioxide, urea).
- Transfers heat around the body to maintain steady body temp
Erythrocytes ( red blood cells)
- contain haemoglobin (red pigment that carries O2 + gives them their colour)
- formed in bone marrow
- transport oxygen from lungs to cells.
- well adapted through biconcave disc shape = large SA:V for O2 to diffuse in/out rapidly
- have no nucleus = more space for haemoglobin to carry O2
-each red blood cell contains 250-300 million molecules o haemoglobin = carry A LOT of O2.
-Haemoglobin can sometimes also carry CO2 produced in respiration back to lungs - the rest transported in plasma.
Platelets
- tiny fragments of large cells called megakaryocytes
[which are found in bone marrow] - Involved in blood clotting
Leucocytes (white blood cell)
- formed in bone marrow
- defend body against infections.
- all contain nucleus + have colourless cytoplasm - some can be stained / some can’t
- Lots of different types of leucocytes
What are the 2 main categories of leucocytes and the types in each one?
- Granulocytes: Leucocytes that have granules in cytoplasm that takes up stain + is obvious under microscope. They have lobed nuclei.
[Non-specific immune system]
-Neutrophils
-Eosinophils
-Basophils
- Agranulocytes: Leucocytes that do not have granules in cytoplasm to take up stain + have unlobed nuclei.
[Specific immune system]
-Monocytes
-Lymphocytes
Granulocytes
[non-specific immune system]
- Neutrophils - engulf + digest pathogens through phagocytosis
Multi lobed nuclei.
[70% leucocytes] - Eosinophils - respond to parasites, allergic reactions, inflammation, developing immunity to disease
[stained red by eosin stain] - Basophils - produce histamines involved in inflammation/allergic reactions.
[have two-lobed nucleus]
Agranulocytes
[specific immune system]
- Monocytes - move out of blood into tissue to form macrophages –> engulf pathogen by phagocytosis.
[largest leucocytes] - Lymphocytes - vital in specific immune response of the body.
[Small leucocytes with very large nuclei]
Can be B or T lymphocytes
