Exchange Flashcards
What is plasma?
What are platelets?
plasma: the watery part of the blood where cells are transported .
Contains dissolved glucose, amino acid, urea, co2 and proteins . Also distributes heat
platelets = clot at the site of wound
What is the purpose of a mass transport system and why do multicellular organisms need one?
maintains the diffusion gradients that bring materials to and from the cell surface membrane
Multicellular organisms need one because:
- the majority of cells are too far from exchange surfaces (outside environment) for diffusion alone to supply or remove their tissue fluid with the various materials needed to keep its composition relatively constant = it would be too slow for it to be by diffusion alone
- larger animals have a low surface area to volume ratio = difficult to exchange enough substances to supply a large volume of an animal through a relatively small outer surface
How does a flattened shape help with exchange
no cell is ever far from the surface
Describe how having a compact shape or a less compact shape is an adaptation for exchange
more compact = small SA: V = minimises heat loss
less compact = large SA:V = increases heat loss
Why do animals with a large surface area to volume ratio have a higher rate of respiration?
to maintain body heat as large SA : V means lots of heat is lost
Describe how gas exchange happens in a single-celled organism
due to being small, these organisms have a large SA: V. Oxygen is absorbed by diffusonacross their body surface, which is only covered by a cell-surface membrane.
CO2 from respiration diffuses out across their body surface
Describe the Tracheal system in insects
Trachea = supported by strengthened rings to prevent them from collapsing
Trachea divide into smaller dead-end tubes = tracheoles
tracheoles extend throughout all the body tissues of the insect = oxygen brought directly to respiring tissues = short diffusion pathway fro the tracheole to any body cell
What is ventilation?
breathing (air being moved constantly in and out of the lungs)
What happens during inspiration? (Diaphragm, intercoastal muscles, ribs, volume of thorax, pressure of the thorax compared to the outside)
Diaphragm muscles contract, causing it to flatten. External intercostal muscles = contract causing the Ribs to move upwards and outwards, which increases the volume of the thorax
the volume of thorax= increases causing a reduction in the pressure of the lungs,
pressure of the thorax compared to the outside= less than outside,so air is forced into the lungs
What happens during expiration? (Diaphragm, intercoastal muscles, ribs, volume of thorax, pressure of the thorax compared to the outside)
Diaphragm muscles relax and domes up.
External intercostal muscles = relax decreasing volume of the thorax causing the ribs to move downwards and inwards, which decreases the volume of the thorax.
due to having elastic tissue, the lung recoils
intercoastal muscles = contract
the volume of thorax= decreases causing an increase in the pressure of the lungs,
the pressure of the thorax compared to the outside= more than outside,so air is forced out of the lungs
What is the main cause of air being forced out
the recoil of the elastic tissue in the lungs
Why do mammals need large volumes of oxygen to be absorbed and large volumes of co2 to be removed?
- they are relatively large organisms with a large volume of living cells
- they maintain a high body temperature which is related to them having high metabolic and respiratory rates
What are lungs?
a pair of lobed strucutres made up of a series of highly branched tubules (bronchioles) , which end up in tiny air sacs (alveoli)
Describe the structure and adaptations of the trachea
flexible airway supported by rings of cartilage, which prevents the trachea collapsing as the air pressure inside falls when breathing in
tracheal walls are made up muscle lined with ciliated epithelium and globet cells = produce mucus to trap dirt particles and have cilia that move the dirt-laden mucus towards the throat
cartilage is c-shaped to give flexibility
What is the bronchi and describe the structure and adaptation of the bronchi
two divisions of the trachea
produce mucus to trap dirt particles and have cilia that move the dirt-laden mucus towards the throat
supported by cartilage= prevents collapsing as the air pressure inside falls when breathing in
What is the bronchicles and describe the structure and adaptation of the bronchicles
series of branching subdivisions of the bronchi
walls are made of muscle lined with epithelial cells
muscle allows them to constrict so that they can control the flow of air in and out of the alveoli
What is the alveoli and describe the structure and adaptation of the alveoli (3 adaptations)
small air sacs at the end of the bronchioles
between alveoli there are some collagen (prevent collapsing) and elastic fibres= allow alveoli to stretch as they gill with air when breathing in
the alveoli are lined with epithelium
alveoli spring back during breathing out in order to expel the carbon dioxide-rich air
What the adaptations of the alveoli for gas exchange
- Red blood cells are slowed as they pass through pulmonary capillaries allowing more time for diffusion
- the distance between the alveolar air and red blood cells is reduced as the red blood cells are flattened against the capillary walls
- the walls of both alveoli and capillaries are very thin and therefore the distance over which diffusion tails place is very short
- alveoli and pulmonary capillaries have a very large total surface area
- breathing movements constantly ventilate the lungs and the action of the heart constantly circulates the blood around the alveoli. together these ensure that a steep concentration gradient of gases to be exchanged is maintained
- blood flow through the pulmonary capillaries maintains a concentration gradient
Describe how ventilation helps to maintain the difference in oxygen concentration between the alveoli and the lung capillaries
Ventilation removes the remaining gas in the alveoli, which has a low concentration of oxygen and a comparatively high concentration of carbon dioxide, and replaces it with fresh atmospheric air, with a high concentration of oxygen and low carbon dioxide.
Describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood ( 6 marks)
- alveoli provide a large surface area
- walls of alveoli thin to provide a short diffusion pathway
- walls of capillary thin/ close to alveoli provides a short diffusion pathway
- walls of capillaries alveoli have flattened cells
- cell membrane permeable to gases
- many blood capillaries to provide a large surface area
- Ventilation maintains a diffusion gradient
- wide trachea
- bronichioles allow efficient flow of air
- cartilage rings keeps airways open
What are the adaptions of the leaf for gas exchange?
- many stomata and no cell is far from a stoma and therefore the diffusion pathway is short
- numerous interconnecting air spaces that occur throughout the mesophyll, so that gases can readily come in contact with mesophyll cells
- the large surface area of mesophyll cells for rapid diffusion.
What is the definition of digestion?
The hydrolysis of large biological products to small biological molecules with the use of enzymes
What is the definition of absorption?
The movement of the molecules from the lumen of the ileum, through the ieum lining into the bloodstream
How is food, in general, digested?
- Buccal cavity = mechanical digestion and mastication (chewing) takes place.
- Saliva in the mouth consists of mucin (binds food together), salivary amylase (digests starch to maltose) and mineral salts (regulates pH around 7, neutral).
- Peristalsis of the circular muscle contracts and relaxes to push food down.
- It usually takes between 4 and 8 seconds for food to travel from mouth to stomach.
- stomach = Mechanical digestion takes place here (churning of the stomach makes food break down in size giving it a larger surface area). While food is in the stomach it mixes with gastric juice by churning. Food in the stomach stimulates stomach wall to produce gastrin (transported in the blood).
- Early small intestine = input of panreatic juices
- muscles in the intestine wall push the food along the ileum
- The large intestine absorbs water (by osmosis), minerals and vitamins.
- Faeces are stored in the rectum and then egested through the sphincter muscle called the anus.
How are carbohydrates digested?
Saliva enters mouth from salivary glands. Salivary amylase produced in the mouth hydrolyse the glycosidic bonds in starch = maltose. This also contains mineral salts that help to maintain the pH at around neutral (optimal pH for amylase)
enters stomach and the acid denature the amylase and prevents further hydrolysis of the starch
food passed into small intestine, mixes with pancreatic juice, which has pancreatic amylase, continues the hydrolysis of remaining starch to maltose. Alkaline salts are produced by pancreas and intestinal wall to maintain the pH at around neutral so that amylase can function.
epithelial lining in intestine wall produces membrane- bound disaccharidase (maltase), which hydrolyses the maltose from starch breakdown into alpha glucose
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What are membrane bound disaccharidases?
maltase that are not released into the lumen of the ileum but is part of the cell-surface membrane of the epithelial cells that line the ileum
How are lipids digested?
They begin digestion in the small intestine
bile salts produced in the liver, stored in the gall bladder, are secreted into the small intestine and emulsify lipids into micelles (tiny droplets) to increase SA of lipids= greater access for lipases
lipases produced in the pancreas are secreted into the small intestine. This hydrolyses the ester bond found in triglycerides to form fatty acids and monoglycerides.
Why is emulsification useful?
because it increases the surface area of the lipids so that the action of lipases is speeded up
How are proteins digested?
Begin digestion in the stomach by endopeptides (hydrolyse peptide bonds in the middle of polypeptides) and break down the polypeptides into smaller peptide bonds
HCL in the stomach maintains the optimum pH for these enzymes
In the ileum of the small intestine where exopeptides released from the pancreas (hydrolyse the peptide bonds found at the ends of polypeptides) = many dipeptides
membrane-bound dipeptidases will hydrolyse the peptide bonds within the dipeptides = amino acids
