Topic 2 - Genes And Health Flashcards
How does air move into and out of the lungs?
Air is drawn into the lungs via the trachea due to low pressure in the lungs, created by an increase in the volume of the thorax as the ribs move up and diaphragm moves down. When the diaphragm muscles and those between the ribs relax, volume decreases, pressure rises and air forced out of the trachea.
Describe how the trachea separates as it moves into the lungs.
The trachea divides into the bronchi which carry air to and from each lung. Within each lung there is a tree like system of tubes ending in narrow tubes, bronchioles, attached to a tiny balloon like alveoli. The alveoli are the sites of gas exchange.
How is mucus made?
It is produced constantly by goblet cells.
What is mucus?
A thick slimy fluid secreted by the cells lining many organs. Mucus is produced, for example, by cells in the gas-exchange system, the digestive system and the reproductive system. Apart from water, its main component is a protein called mucin. Mucus acts as a lubricant and as a protective layer.
What does mucus do in the walls of the airways?
Any dust, debris or microorganisms that enter the airways become trapped in the mucus.
What happens to the mucus in the airways?
It is continuously removed by the wave-like beating cilia that cover the epithelial cells lining the tubes of the gas exchange system.
What is the difference in the mucus of CF sufferers? What problems does it cause?
People who have CF have mucus that contains less water than usual resulting in a sticky mucus that the cilia find difficult to move. This sticky mucus in the lungs has two major effects on health. It increases the chance of lung infection and makes gas exchange less efficient.
Describe the structure of a part of the lung e.g a part of the bronchi
- Basement membrane holds the cell in position
- ciliated epithelial cells lining the airway attached to the basement membrane
- goblet cells in epithelial cells produces mucus which is released into the airway
- Cilia, hair like structures, beat and move mucus up and down out of the lungs.
What is the epithelium?
Tissue which forms the outer surface of many animals. Epithelial cells also line the cavities of organs such as the gut and lungs. The epithelium consists of one or more layers of cells sitting on a basement membrane. These cells may be flat (squamous or pavement epithelium) or tall in shape (columnar epithelium).
What are the different types of epithelia?
- Squamous /pavement
- columnar epithelium
- ciliated epithelial cells
Where are ciliated epithelial cells found and what are there properties?
In the trachea, bronchi and bronchioles there are ciliated epithelial cells with cilia on the apical surface. These cilia beat in a coordinated way like a Mexican wave and move substances along the tube they line.
How does sticky mucus increase the chance of lung infections?
Microorganisms become trapped in the lungs and some of these microorganisms cause illness (pathogens). The mucus is normally moved by the cilia into the back of the mouth cavity where it is either coughed out or swallowed and then killed in the stomach but in CF sufferers the layer of mucus is so sticky that the cilia cannot move it. Mucus production continues and the layers of thickened mucus build up in the airways. With low levels of oxygen in the thick mucus, harmful bacteria are able to thrive in these anaerobic conditions.
What causes mucus to become even thicker and stickier?
White blood cells fight the infections within the mucus but they die break down and release DNA that makes the mucus even stickier.
What is the problem with having repeated lung infections?
Repeated lung infections can eventually weaken the body’s ability to fight the pathogen and cause damage to the structures of the gas exchange system.
Living organisms have to exchange substances with their surroundings. Give examples
They take in oxygen and nutrients and get rid of waste materials such as carbon dioxide.
What is the difference between unicellular and multicellular organisms regarding the exchange of gases?
In unicellular organisms the whole surface membrane is the exchange surface. Larger multicellular organisms have more problems absorbing substances because of their size of the organisms surface area to volume ratio. If larger organisms relied only on their general body surface for exchange of substances they could not survive because the distance to the innermost tissue is too far for diffusion to supply oxygen quickly enough; change would be too slow.
What happens to the surface area to volume ratio as organisms get larger?
The surface area per unit of volume gets less.
What is diffusion?
The net movement of particles from a high concentration to a low concentration until equilibrium has been reached.
How do you work out total surface area to volume ratio?
Organisms total surface area / volume
What are the key features for efficient gas exchange?
- Large surface area of the alveoli
- Numerous capillaries around the alveoli
- Thin walls of the alveoli and the capillaries meaning a short distance between the alveolar air and blood in the capillaries
- Steep concentration gradient
What does the rate of gaseous exchange depend on?
- Surface area - Rate of of diffusion is directly proportional to the surface area. As the surface area increases the rate of diffusion increases.
- Concentration gradient - Rate of diffusion is directly proportional to the difference in concentration across the gas exchange surface. The greater the concentration gradient the faster the diffusion.
- Thickness of the gas exchange surface - rate of diffusion is inversely proportional to the thickness of the gas exchange surface. The thicker the surface the slower the diffusion.
What is the calculation for rate of diffusion?
Surface area x Difference in concentration / thickness of the gas exchange surface
What is Fick’s law?
The relationship between the properties that affect the rate of diffusion (surface area, concentration gradient, thickness of gas exchange surface)
What are the properties of the alveoli that make them so good at the exchange of gases?
The large surface area of the alveoli, the steep concentration gradient between the alveolar air and the blood (maintained by ventilation of the alveoli and continuous flow of blood through the lungs) and the thin walls of the alveoli and the capillaries, combine to ensure rapid diffusion across the gas exchange surface.
How does the sticky mucus layer affect gas exchange?
- The sticky mucus layer in the bronchioles of a person with cystic fibrosis tends to block these narrow airways, preventing movement of air into the alveoli beyond the blockage. This reduces the number of alveoli providing surface area for gas exchange. Blockages are more likely at the narrow end of the airways. The se blockages will often allow air to pass when the breaths in but not when they breath out, resulting in the over inflation of the lung tissue beyond the blockage. This can damage the elasticity of the lung.
- People with CF also struggle when does physical exercise as the gas exchange system can not deliver enough oxygen to the muscle cells which is needed for aerobic respiration to provide energy.
Why is mucus so sticky (CF)?
It contains less water than normal. The reduced water level is due to abnormal salt (sodium chloride) and water transport across the cell surface membranes caused by a faulty transport protein channel in the membrane.
What are the functions of proteins in our body?
- Antibodies
- Enzymes
- Hormones
- Structural proteins (hair, nails, muscle, ligaments, tendon, hair)
- Components of cell membranes and have important functions in membranes
What make up proteins?
Amino acids
How many different types of amino acids are there?
20
Plants can make all 20 amino acids but animals can only make some. The amino acids that animals have to obtain are known as?
Essential amino acids
Describe the general structure of an amino acid.
In every amino acid a central carbon atom is bonded to an amine group (-NH2), a carboxylic acid group (-COOH), a hydrogen (-H) and a residual group (-R). Each different amino acid has a different acid group.
What is a condensation reaction?
A type of chemical reaction in which small molecules are joined together with the removal of a molecule of water. Condensation is involved in forming biologically important polymers. The reactions in which amino acids join to form proteins, and glucose molecules join to form starch and cellulose are examples of condensation reactions.
What do two amino acids form?
A dipeptide
What is a dipeptide?
A molecule that is made up of two amino acids joined by a peptide bond.
What is a peptide bond?
The bond joining two amino acids in a protein. Amino acids join together by condensation. When a protein is digested, the peptide bonds are broken down by hydrolysis.
What is a a primary structure?
The sequence of amino acids in a protein or polypeptide is known as the primary structure. The primary structure will determine how the polypeptide will fold. There are twenty different amino acids and they can be combined in different ways to produce many different proteins.
The peptide bond forms between…
The carbon and nitrogen
What is the secondary structure?
Chain of amino acids my twist to form an alpha helix or come together in beta pleated sheets due to hydrogen bonds between the amine and acid group.
What is an alpha helix?
- They have the shape of extended springs
- Held together by hydrogen bonds
- N-H donates a hydrogen atom to the C=O group
What are belated pleated sheets?
Amino acid chains fold back on themselves or several lengths of chain may link with hydrogen bonds holding the parallel chains in an arrangement known as a beta pleated sheet.
In a beta pleated sheet are the hydrogen bonds strong or weak?
Each hydrogen bond is weak but multiple keep it stable.
Does a protein only contain an alpha helix or a beta pleated sheet?
No, a protein can contain sections of alpha helixes and sections of beta pleated sheets.
What is a tertiary structure?
Entire 3D protein held together by bonds between R groups.
What types of bonds hold the tertiary structure together?
Ionic and covalent
What maintains the tertiary structure?
Chemical bonds and hydrophobic reactions between R groups maintain the tertiary structure of the protein.
When is an R group polar?
When the sharing of electrons is uneven.
Where are non-polar R groups faced in a protein?
Non-polar R groups (hydrophobic) face the inside of the protein, excluding water from the centre of the molecule.
In a folded structure what can happen to the R groups?
Chemical bonds can form between R groups that are close to each other in a folded structure.
When is a molecule described as a protein?
When the 3D structure is functional. Meaning the molecule is able to perform a specific function.
What is the quaternary structure?
Proteins made up with multiple polypeptide chains held together.
What are conjugated proteins?
Proteins with another chemical group associated with their polypeptide chains.
Give an example of a conjugated protein
Myoglobin and haemoglobin because they are an iron containing group.
What are the two types of proteins?
Globular and fibrous
What is the shape of fibrous and globular proteins?
Fibrous - Long and narrow
Globular - Rounded / spherical
What is the role of fibrous and globular proteins?
Fibrous - Structural (strength and support)
Globular - Functional (catalytic, transport)
What is the solubility of fibrous and globular proteins?
Fibrous - Insoluble in water
Globular - soluble in water
What is the sequence like in fibrous and globular proteins?
Fibrous - Repetitive amino acid sequence
Globular - Irregular amino acid sequence
What is the stability of fibrous and globular proteins?
Fibrous - Less sensitive to changes in heat, pH, etc
Globular - More sensitive
Give examples of fibrous proteins
- Collagen
- Myosin
- Fibrin
- Actin
- Keratin
- Elastin
Why are globular proteins soluble and fibrous are not?
In globular proteins the hydrophobic R groups are folded into the core of the molecule, away from the surrounding water molecule, making them soluble. In fibrous proteins the hydrophilic R groups are exposed and therefore the molecule is insoluble.
What is a phospholipid? Describe its properties.
A phospholipid molecule is a lipid with two distinct sections. It has a head region consisting of glycerol and a phosphate group. This part of the molecule is attracted to water. The other end consists of two fatty acid tails. This end of the molecule repels water. Phospholipids are important components of cell membranes where they are arranged in a bilayer with the heads pointing outwards and the tails pointing towards each other.
Which part of the phospholipid bilayer is polar?
The head is polar as one end is slightly positive and the rest is slightly negative. The phosphate head is hydrophilic and attracts to other polar molecules.
Which part of the phospholipid bilayer is non-polar?
The fatty acid tails are non-polar, therefore are hydrophobic.
What happens when phospholipids are place on water?
The hydrophobic tails stand up vertically out of the water while the hydrophilic heads stay in the water.
What happens when the phospholipids are placed in water?
They may become arranged into a spherical cluster called a Michelle or form a bilayer. They tend to form bilayer because the tow fatty acids are too bulky to fit into the centre of the micelle.
Describe the formation of a phospholipid bilayer.
A lipid bilayer will tend to close in on itself so that there are no ends with exposed hydrocarbon chains, thus forming compartments as happens around and within cells. Hydrophobic fatty acid tails have no contact with water on either side (cytoplasm in the cell or aqueous tissue fluid) of the membrane and the hydrophilic phosphate heads remain in contact with the aqueous environment.
What do membranes contain?
- Glycolipid - lipid molecules with polysaccharides (no branches)
- Channel protein
- Glycoprotein - Protein molecules with polysaccharides (like a tree)
- Proteins - some are fixed others are free to move
- Cholesterol - inside the phospholipid bilayer
- Carrier proteins
- Enzymes
What are peripheral proteins?
Loosely attached proteins on the outside of the surface of the membrane.
What are integral proteins?
Fully embedded proteins within phospholipids, some even spanning both layers.
What are most integral proteins like?
Regions at their ends have polar hydrophilic amino-acids with the middle portion being mainly composed of non-polar hydrophobic amino acids.
When is the membrane more fluid? Why?
The more unsaturated a phospholipid the more fluid it is. The greater the ratio of phospholipids that contain unsaturated fatty acids to saturated fatty acids, the more fluid the membrane will be. The is because unsaturated phospholipid tails have ‘kinks’ preventing them from packing closely together, this allows more movement to take place.
How do substances pass through cell membranes?
- Diffusion
- Osmosis
- Active transport
- Exocytosis
- Endocytosis
When does diffusion occur?
Occurs when there is a concentration gradient
What types of molecules pass through cell membranes by diffusion?
Small molecules diffuse directly across the cell membrane (e.g oxygen/carbon dioxide) and hydrophobic substances.
What type of process is diffusion?
It is passive
Diffusion occurs across a … (membrane)
Phospholipid bilayer
What is facilitated diffusion?
Diffusion is the movement of a substance from where it is in a high concentration to where it is in a lower concentration. Large molecules and ions can only cross cell membranes with the aid of carrier proteins. This form of diffusion is called facilitated diffusion.
What molecules pass through a cell membrane by facilitated diffusion?
Large olecules or hydrophilic (polar) molecules - they cannot simply diffuse through a phospholipid bilayer.
What type of process if facilitated diffusion?
Passive -> no metabolic energy is needed for diffusion to occur.
What are the proteins that aid facilitated diffusion?
- Channel proteins
- Carrier proteins
What are channel proteins?
A protein that spans a membrane and is involved in the transport of molecules across the membrane.
How do channel proteins work?
They allow polar molecules to diffuse through a membrane. Different channel proteins with different shapes for different proteins.
What is a type of channel protein?
A gated channel which is a channel protein that opens and closes.
What is a gas exchange surface?
The layer across which oxygen and carbon dioxide are exchanged.
What is a carrier protein?
A protein that binds with a specific ion or molecule and helps it cross a membrane.
How does a carrier protein work?
The protein changes shape allowing the molecule to be transported across the membrane.
What is osmosis?
The net movement of water molecules from a solution of high concentration of solute to a low concentration of solute across a partially permeable membrane.
What molecules pass across a cell membrane by osmosis?
It is the movement of free water molecules
What is the type of process of osmosis?
It is a passive process through a phospholipid bilayer.
What is active transport?
Movement of molecules across a membrane against a concentration gradient (from low to high) and energy is required.
How does active transport work?
Carrier proteins move the molecule along with ATP (Adenosine Triphosphate) to provide the needed energy.
What is ATP? How is it formed?
Adenosine Triphosphate provides the immediate source of energy for all biological processes. It is formed during respiration, when fats and carbohydrates are broken down.
How does active transport occur?
ADP forms from the hydrolysis of ATP between the third and second phosphate group. Once removed the phosphate group becomes hydrated and a lot of energy is released as bonds form between water and phosphate. The energy released changes the shape of the carrier protein allowing the movement against the concentration gradient across a membrane.
What is exocytosis?
A process which involves the transport of substances out of cells. The vesicles move through the cytoplasm and fuse with the cell surface membrane, releasing the protein from the cell.
