Topic 3B - More Exchange And Transport Systems Flashcards
Define digestion
The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across the cell membranes
Which enzymes are involved in carbohydrate digestion
Amylase found in the mouth
Maltase sucrase and lactase found in the membrane of small intestine
What are the substrates and products of the carbohydrate digestive enzymes
Amylase - starch into smaller polysaccharides
Maltase - maltose into 2 glucose
Sucrase - sucrose into glucose and fructose
Lactase - lactose into glucose and galactose
Where are lipids digested
The small intestine
What needs to happen before lipids can be digested
They must be emulsified by bile salts produced by the liver. This breaks down large fat molecules into smaller, soluble molecules called micelles, increasing the surface area.
How are lipids digested
Lipase hydrolyses the ester bond between the monoglycerides and fatty acids
Which enzymes are involved in protein digestion? What area their roles?
Endopeptidases - break between specific amino acids in the middle of a polypeptide
Exopeptidases - break between specific amino acids at the end of a polypeptide
Dipeptidases - break dipeptides into amino acids
Which molecules require co-transport
Amino acids and monosaccharides
Explain how sodium ions are involved in co-transport
Sodium ions are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with Na+ ions
Describe the structure of haemoglobin
Globular, water soluble, consists of 4 polypeptide chains, each carrying a haem group
Describe the role of haemoglobin
Present in RBC. Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues
Name three factors affecting oxygen-haemoglobin binding
- Partial pressure / conc of oxygen
- Partial pressure / conc of carbon dioxide
- Saturation of haemoglobin with oxygen
How does partial pressure of oxygen affect oxygen-haemoglobin binding
As partial pressure increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin
How does partial pressure of carbon dioxide affect oxygen-haemoglobin binding?
As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin. This is known as the Bohr effect
Explain why oxygen binds to haemoglobin in the lungs
Partial pressure of oxygen is high
Low concentration of carbon dioxide in the lungs so affinity is high
Explain why oxygen is released from haemoglobin in respiring tissues
Partial pressure of oxygen is low
High concentration of carbon dioxide in respiring tissues, so affinity decreases
What does the oxyhaemoglobin dissociation curve show
Saturation of oxygen against the partial pressure of oxygen
How does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve
Curve shifts to the right because haemoglobin affinity for oxygen has decreased
What is the structure of the atria and ventricles and how does it help to perform its function
Atria: Thin, elasticated walls so they can stretch when filled with blood, increasing the force of contraction
Ventricles: thick muscular walls pump blood under high pressure. The left ventricle is thicker than the right because it has to pump blood all the way around the body
What is the structure and function of the arteries
Thick walls - handle high pressure without tearing
Muscular and elastic - to control blood flow
What is the structure and function of the veins
Thin walls - low pressure
Valves - prevent backflow of blood
Less muscular and elastic tissue - don’t have to control blood flow
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing pressure and opening the atrioventricular valves. Allows blood to flow through the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valve remains closed
Describe what happens during atrial systole
The atria contract, pushing blood out into ventricles
Describe what happens during ventricular systole
The ventricles contract . The pressure increases, closing the AV valves to prevent back flow and opening the semilunar valves. Blood flows into the arteries
Name the nodes involved in heart contraction and where they are situated
Sinoatrial node - wall of right atrium
Atrioventricular node - in between the two atria
What does myogenic mean
The hearts contraction is initiated within then muscle itself, rather than by nerve impulses
Explain how the heart contacts
SAN initiates and spreads impulse across the atria, so they contract
AVN receives the impulse and delays it by 0.1 seconds, then sends the signal down the bundle of HIS.
The impulse travels into the punkijne fibres which branch across the ventricles, so the contract from the bottom up.
Why does the impulse need to be delayed
To allow for all the blood to pass through and for the valves to close
What is tissue fluid
A watery substance containing glucose, amino acids, oxygen, and other nutrients. It supplies these to the cells, while also removing any waste materials
How is tissue fluid formed
As blood is pumped through increasingly small vessels, this creates hydrostatic pressure which forces fluid out of the capillaries. It bathes the cells and then returns to the capillaries when the hydrostatic pressure is low enough.
How is water transported in plants
Through xylem vessels; long, continuous columns that also provide structural support to the stem
Explain the cohesion-tension theory
Water molecules form hydrogen binds with each other, causing them to ‘stick’ together. The surface tension of the water also creates a sticking effect. Therefore as watery is lost through transpiration, more can be drawn up the stem.
What is cardiovascular disease?
General term used to describe diseases associated with the heart and blood vessels
Name 4 cardiovascular diseases
Atheroma
Aneurysm
Thrombosis
Myocardial infarction
What is atheroma?
Build up of white blood cells, lipids and connective tissue which hardened form a fibrous plaque
What is an aneurysm?
A balloon like swelling of the artery
What is a thrombosis?
Formation of a blood clot
What is a myocardial infarction?
If coronary artery beco,es blocked an area of the heart wont receive oxygen
What are some risk factors of cardiovascular disease?
High blood pressure
High blood cholesterol and poor diet
Cigarette smoking
What does the xylem transport?
Water and minerals in solution
What does the phloem transport?
Organic substances like sugars (up and down the plant)
What is transpiration?
Evaporation of water from a plants surface
What are the 4 factors that affect the rate of transpiration?
Light intensity
Temperature
Humidity
Wind
Make one for estimating transpiration rate
What is the structure and function of a phloem?
Sieve tubes - form the tube for transporting cells, have no nucleus and a few organelles
There’s a companion cell for each sieve tube element, carry out living functions for sieve cells
Transports organic substances
What is translocation?
Movement of solutes to where they are needed in a plant
What occurs during translocation?
Moves solutes from sources to sinks
What is the source?
Where assimilates are produced
Where is the sink?
Where assimilates are used up
Briefly explain mass flow hypothesis? (Source, sink, flow)
Source: active transport is used to actively load solutes from companion cells into the sieve tubes of the phloem at the source, lowering water potential so water enters
Sink: solutes removed from phloem to be used up, this increases water potential so water leaves the tubes
Flow: this creates a pressure gradient from the source to the sink end. Gradient pushes solutes towards sink. When they reach the sink they will be used
