Exchange Substances new set Flashcards
(42 cards)
Talk about the role of the mouth in the digestive system.
The first stage of the digestive system where food is broken down into smaller pieces by chewing. This is an example of Mechanical Digestion. The teeth cut and crush the food. Its then mixed with saliva which is made in the Salivary Glands to form a ball of food called a bolus.
Chemical Digestion also occurs here- enzymes in the saliva begin to process the breakdown. The enzyme found in Saliva is called amylase. This is a type of carbohydrase that breaks down carbohydrates into maltose which can further be broken down into Glucose by maltase to be used as energy for processes like respiration.
Talk about the oesophagus’ role in the digestive system.
long tube that connects the mouth to the stomach. Food is moved through the system by the process of peristalsis. The muscles in the wall of the oesophagus work together to produce wave-like contractions which have a squeezing-action that pushes the bolus through the gut.
Talk about the Stomach’s role in the digestive system.
Mechanical- muscles in the stomach walls contract, churning the food and breaking it into smaller pieces.
Chemical- enzymes secreted from the stomach lining, as well as the pancreas, aid the breakdown of molecules. The main enzymes found are proteases: these digest proteins into amino acids.
The stomach also produces hydrochloric acid. This kills many harmful microorganisms that may have been swallowed along with the food. It also maintains the optimum ph. for the enzymes, which is in acidic conditions.
Talk about the livers role in the digestive system.
The liver produces bile which helps emulsify fats into forms that can be absorbed called fatty acids. It also helps to neutralize stomach acid so its at an optimum PH for enzyme action.
Talk about the Pancreas’ role in the digestive system.
Secretes pancreatic enzymes that break down molecules and also produces hormones such as glucagon and insulin which regulates the level of glucose in the blood.
Talk about the small intestines (ileum’s) role in the digestive system.
A long muscular organ where food is further digested by enzymes produced by its walls and absorbs the products of digestion into the bloodstream to be used.
What are some adaptations of the ileum?
Villi- foldings in the inner walls:
These increase surface area to volume ratio for maximum absorption and transport. it is further increased by millions of tiny projections on the villi called microvilli.
They have thin walls to reduce the overall distance over which diffusion takes place and are well supplied with blood to maintain a diffusion distance.
Talk about the role of the large intestine and the rectum in the digestive system?
The large intestine absorbs excess water that has been passed through the digestive system which then leads to the rectum where the waste is stored before being remobed via the anus in excretion.
What is the process of carbohydrate digestion?
- Saliva from salivary glands enters the mouth whoch contains salivary amylase which starts hydrolysing any statcg in the food into maltose.
2.The food enters the acidic stomach denaturing anylase and preventing further hydrolysis - Food is passed into the ileum where it mizes with pancreatic amylase to hydrolyse the remaining starch
- Muscles in the intestine wall push food along the ileum where maltase on the epithelial lining hydrolyses the maltose into glucose.
This also happens with sucrose and lactose.
What is the process of protein digestion?
Proteins are digested via proteases:
Endopeptidases- hydrolyses the peptide bonds between amino acids in the centre of proteins
Exopeptidases- Hydrolyses the peptide bonds on the terminal amino acids
Dipetidases- Hydrolyses the bonds between two amino acids of a dipeptide found on the surface of epithelial cells.
Talk about Lipid digestion
Lipases hydrolyse lipids which are produced in the pancreas that hydrolyse the ester bond found in triglycerides.
1. Bile salts emulsify lipids into monoglcerides and fatty acids which stay associated with the salts forming micells.
2. When micells reasch the lining and release the products to easily diffuse accross the epithelial cells.
3. Once in the cells, they are recombined to form triglycerides in the endoplasmic reticulum.
4. In the Golgi, triglycerides are assosiated with cholestreol to form structures called chylomicrons which move out of the cell via exocytosis into capillaries.
How are plants adapted for efficient gas exchange?
Stomata- open and close due to guard cells which allow gas to enter and leave the leaves
Air Spaces- Have a large surface area to volume ratio in the mesophyll for rapid diffusion.
What are xerophytic plants and how are they adapted to water loss?
Stomata- sunken and contain stomatal hairs to maintain humid air for a concentraion gradient
Tick cuticle so less water can escape
Rolling of leaves- protects the lower epidermis from the outside and so that area becoms trapped with humid air so it has a high water potential.
Reduced leaf surface area reduces surface area to volume ratio so there is less area for stomata to talke up
Talk about gas exchange in Fish.
Fish have a small surface area to volume ratio as well as a waterproof, gas-tight outer covering for gas exchange. Thus meaning that their surface is not adequate to supply and remove respitory gases so they have an internal sturcture.
Each gill is supported by an arch, along the arch there are multiple projections called gill filaments with lamellae on them which participate in gas exchange.
Blood and water flow accross the lamella in a counter current direction meaning they flow in the opposite direction to one another. This ensures a steep diffusion distance is maintained so the mazimum amount of oxygen is diffusing into the deoxygenated blood from the water.
The projections are held apart by water so out of water they stick together meaning fish cant survive
ventilation is required to maintain a continuous unidirectional flow. It begins with the fish openin uts mouth allowinf water to flow in. When the fish closes its mouth, the buccal cavity raises which increases the preassure and water is forced over the gill.
Talk about gas exhange in insects.
Insects do not possess a transport system therefore oxygen needs to be transported directly to the tissues.
spiracles, small openings of the tubes allow gas in which then go through a network of tubes called trachae which are supported by strengthened rings. They divide into small tubes called tracheoles which extend through all the body tissues of insects directly, reduces diffusion pathway. There are three different ways of movement:
along diffusion gradient- conc of oxygen at end of tracheoles falls creating diffusion distance
mass transport- contracting muscles
water- ends are filled with water, decreases volume of tracheoles and draws water in
Talk about the mammolian gas exhange system?
The lungs are a pair of lobed syructures which have a large surfave area. They are surrounded by a rib cage to protect them and they are able to inflate. External and internal intercostal muscles are between the ribs which contract and lower them. The diaphram separates the lungs
Air enters though the nose, along the trachea, bronchi and bronchioles, which are structures that enable a passage of air into and out of the lungs. They are held open with rings of cartilage.
Alveoli is where gas exchange actually takes place. These are adapted:
Thin- reduces the diffusion pathway for gases
Constant blood supply- steep concentration gradient
300 million alveoli to increase surfave area
Talk about ventilation.
Ventilation is the flow of air in and out of the alveoli:
INSPIRATION- The external intercostal muscles contract and the internal muscles relax. This cayses the ribs to move upwards. The diaphram contracts and flatterns. Both of these cayse the volume of the thorax to increase, lowering the preassure creating a gradient and allowing air to be forced into the lungs
EXPIRATION- The internal intercostal muscles contrat and external muscles relex which lowers the rib cage. The diaphram relaxes and raises upwards. These actions decrease the volume inside the thorax increasing preassure and forcing air out of the lungs
Talk about the Xylem.
The xylem transports water and solutes from the roots to the leaves.
They are long tubes that run up the stem of plants. They are made of dead cells called vessel elements which are stacked on top of one another and have no cell walls at the end of each element creating a continuous tube for water flow. The walls are lined with a waterproof polymer called lignin which reinforces the walls to provide structural support
What is Transpiration?
The process where plants absorb water through the roots which then moves up through the plant and is released into the atmosphere through pores in the leaves.
The humidity of the atmosphere is usually less than that of the air spaces next to the stomata. As a result, there is a water potential gradient between the spaces and the air allowing water to diffuse out. This water is replaced by water evaporating from the cell walls into the mesophyll cells.
Transpiration lowers the water potential of the leaves so water is replaced via osmosis to continue the movement of water up the stem.
Talk about the movement of water in the root.
Water enters the plant through root hair cells and moves into the xylem located in the centre of the root. This movement occurs due to a water potential gradient. As the water potential is higher in the soil than the root hair cells due to dissolved substances in the cell sap. This is via osmosis.
What are the two ways water moves from the root to the xylem?
SYMPLASTIC PATHWAY- water enters the cytoplasm through the membrame and asses from one cell to the next through the plasmodesmata.
APOPLASTIC PATHWAY- water moves through the water filled spaces between cellulose molecules in cell walls. Water doesnt pass through any plasma membrane so can carry dissolved mineral ions and salts
When water reaches a part of the root called the endodermis, it encounters a layer of suberin known as the Casparian Strip which cant be penetrated by water, therefore for the water to cross the endodermis, the water has been moving through the cell walls must enter the symplastic pathway.
Talk about Cohesion-Tension Theory.
Main factor responsible for the movement of water up the xylem.
1. Water evaporates from mesophyll cells due to transpiration
2. Water molecules form hydrogen bonds between one another and hence tend to stick together. This is known as cohesion.
3. The loss of water from the leaves creates tension as hydrogen bonds also form between water molecules and the side of the vessel
4. As water evaporates from the leaf into air spaces, more molecules of water are drawn up behind it due to this cohesion forming a continuous colum of water called a transpiration flow.
5. When water is pulled up the stem, the water potential at the bottom of the plant decreases. Water can now diffuse into the roots via osmosis down the water potential gradient
Mineral ions are actively transported into root hair cells creating a negative water potential and allowing root pressure to further push water up the column.
Talk about the role of the Phloem
The phloem is the tissue responsible for transporting organic substances in plants up or down a plant to where ever it’s needed in a process called Translocation
The Phloem is made of long thing structures called sieve elements connected end to end. These end walls are perforated to form sieve plates which help sap movement and are associated with companion cells
What is the process of mass flow theory?
Mass Flow Theory – Step-by-Step
✅ Step 1: At the Source (e.g. Leaves)
Glucose produced during photosynthesis is converted into sucrose.
Sucrose is actively transported into sieve tube elements by companion cells using ATP.
This lowers the water potential inside the sieve tubes.
Water enters by osmosis from nearby xylem vessels into the phloem.
This creates a region of high hydrostatic pressure at the source end of the phloem.
✅ Step 2: Mass Flow Through the Phloem
The phloem sap (sucrose + water) moves down the hydrostatic pressure gradient, from source to sink.
This movement is passive, but depends on active loading (at source) and active unloading (at sink).
✅ Step 3: At the Sink (e.g. Roots, Fruits, Growing Areas)
Sucrose is actively removed from sieve tubes by companion cells into sink cells.
This raises the water potential in the sieve tubes at the sink.
Water leaves the phloem by osmosis, entering surrounding cells or returning to the xylem.
This creates low hydrostatic pressure at the sink end.
