Topic 4 Flashcards
What does decrease in SA mean?
There is less surface area for the exchange of materials due to many cells being in contact with each other.
The higher the surface area to volume ratio
The more efficient diffusion is
What happens to SA:V when oraganism increase in size.
What does this mean?
It decreases.
Diffusion is less efficient.
Why is diffusion more efficient in small organisms?
●The diffusion distance is short.
●The SA:V is large.
●Metabolic demands are low.
What factors affect diffusion?
-The area of diffusion.
-The thickness of surface over which diffusion takes place.
-The difference in concentration.
Why is diffusion less efficient in large organisms?
They have a low SA:V
What are the adaptations to SA:V?
Large Surface Area.
Thin membrane.
Transport Systems.
What does large surface area do?
It allows more of a substance to diffuse at the same time.
Why is a thin membrane important?
It reducese diffusion diatance.
Why are transport systems useful?
They move substance around and facilitate exchange.
It allows a higher concentration gradient to be maintained.
What does a steep concentration do?
It increases the rate of transport.
What enhances a cells ability to absorb nutrients by providing more space for transport proteins and channels?
Surface area
Why do large organisms need mass transport system?
To maintain a concentration gradient for diffusion.
High metabolic demand.
Why do large organisms need specialised gas exchange organisms?
high surface area.
minimizes diffusion distance.
ensure continuous O₂/CO₂ exchange.
Describe the fluid mosaic model.
Fluid” = Phospholipids are constantly moving, making the membrane flexible.
“Mosaic” = Membrane is composed of proteins, cholesterol, and carbohydrates embedded in the bilayer.
Describe the phospholid bilayer.
Hydrophilic phosphate heads face outward (towards water-based cytoplasm & extracellular fluid).
Hydrophobic fatty acid tails face inward (repel water, forming a barrier).
Allows small, non-polar molecules (O₂, CO₂) to diffuse but prevents large/polar molecules & ions from passing.
What is the intergral protein?
Allow facilitated diffusion (channel) or active transport (carrier) of large/polar molecules & ions.
Span the bilayer (e.g., channel & carrier proteins).
What is an Extrinsic (Peripheral) Protein?
Found on the surface of the membrane or embedded partially.
Act as receptors or cell recognition sites.
Why is the cholesterol present in the cell membrane?
Regulates membrane fluidity (prevents it from becoming too rigid or too fluid).
Increases stability by binding to phospholipid tails, making the membrane less permeable.
What is a glycoprotein?
Protein + carbohydrate chain (act as cell receptors).
What is a glycolipid
Lipid + carbohydrate chain (involved in cell recognition).
What are the 3 forms of passive movemet accross membrane?
Diffusion
Facilitated diffusion
Osmosis
What does high concentration mean?
That there are more particles in one area than another.
What is the net movement ?
High concentration to low.
What is diffusion?
This is the movement of small,non-charge molecule frok regions of hugh conc to regions of low concentration.
What is facilitated diffusion?
The movement of large, charged or polar molecules through channel proteins down a concentration gradient.
How do channel proteins carry out their function?
They provide a water filled channel to allow the difussion of hydropholic substances through the hydrophobic tail.
How do carrier proteins work?
They are specific for a particular molecule according to their shape.
The carrier picks up molecule, and changes shape, moving the molecule it picked up with it. It then releases the molecule on the other side of the membrane.
What is equilibrium across a memebrane?
If the concentration is the same on both sides, the net movement is zero even though particles diffuse in both direction all the time.
What is osmosis
It is the net movement of water (and other solvents) through a partially permeable membrane.
What is turgor pressure?
The inward pressure of the cell wall on the cytoplasm.
How does tugor pressure function?
It cancels out the tendency for water molecules to move in.
How are larger molecules or bulk substances transported using vesicle-meduated processes.
- Exocytosis
-Endocytosis
What is Endocytosis?
The cell membrane engulfs the molecules to form a vesicle being transported into the cell.
What is Exocytosis?
The vesicle fuse with cell membrane, releasing their content into the extracellular space.
What is Active Transport.
AT is the movement of molecules or ions across a membrane from a region of low to high conc, against the conc gradient.
Outline the process of active transport.
- Proteins in memebrane act as carriers. Often, they are specific to the molecules being transported. They only transport the molecules in one direction.
- The release of energy from the hydrolysis of ATP causes a change in shape of the carrier protein, moving the molecules from one side of the membrane to the other.
- The protein carrier then returns to its original shape [passively] to allow more molwcules to enter.
What is the role of ATP?
It provides energy for biological processes, cell divisions, protein synthesis
When ATP is hydrolysed what is formed
ADP and inorganic phosphate.
How does ADP become ATP
Phosphorylation using energy needed to add P to ADP
ATP can be quickly regenerated.
True or False.
True
ATP allows for what?
Cells to carry out essential functions efficiently and in a controlled manner.
What is the gas exchabge ststem in insects
Tracheal system
How does gas exchnege occur in insects.
It occurs directly between the air and body tissues without blood for transport.
Describe the Trachea
It is a tube lined with spirals of chitin, which keeps it open and impermeable to gases.
Describe the treacheoles
It is spread through the insect tissue and individual cells.
They have no chitin, so are freely permeable to gases.
Describe the Spiracle
Pores on the exoskeleton which open and close by sphincters to control water loss and regulate gas exchange.
Describe the tracheal syatem of an insect.
Oxygen diffuses into the trachea through the spiracles and then into tracheoles.
It then travels into the cells of the organs.
Where does gas exchabge happen in insects
Tracheoles.
What is mechanical ventilation
The rhythmic body movement in marge, very active insects, the abdomen is pumped in andvout to draw in more air.
What do the thousands of tiny tracheoles provide?
Large surface area.
Where does gas exchange occur in fish?
Gills
Water is denser than air so has less O2
True
Water flows over to the gills of fish in one direction.
True
Describe the process of through-flow ventilation in bony fish.
● The pressure in the mouth cavity is reduced by the floor if the mouth being lowered and the operculum moves outwards.
● The operculum acts as a vlve as it is pressed against the body wakl by the hugher putaide pressure, water enters mouth to equalise the pressure.
●The volume of the buccal cavity is reduced and pressure increases as the floor of the mouth is raised. Opercular valve prevents water from leaving.
●the incresed pressure opens the operculhm and water leaves through gill filaments
How do cartilaginous fishes ventilate, i.e sharks
They do not have an operculum, and so they swim constantly to kwep water flowing across gills.
Gill filaments are made of what?
Lamellae.
Adaptation of Gills
Lamallae provides large durface area and short diffusion path for gases.
Describe the Counter-Current Flow.
Gas exchange must have what?
Large surface area, thin membrane and maintain steep conc gradient.
In mammals gas exchange occurs where
In the lungs
Lungs adapted via
Alveoli
Alveoli
Madeup of single layer of flattened epithelial cell[ 1 cell thick], so provides short diffusion distance
Surrounded by capillaries containing deoxygenated, so there is steep concentration gardient.
Lined with moisture , allowing gases to dissolve and diffuse easily.
Contains elastic fibres to help recoil after stretching during inhalation.
Ventilation
Breathing movement ensures fresh air enters and stale air is removed, maintaining steep conc gradient.
Inhalation
Diaphragm contracts and flattens
Intercostal muscles contract
Ribcage moves up and down
Thoracic volume increases,
Pressure decreases.
Air is drawn in.
Exhalation
Diaphragm relaxes
Intercostal muscle relax
Ribcage moves down and in
Thoracic volume decreases, pressures increases
Air is forced out.
