Topic three- Exchange

Define respiration

A biochemical process by which ATP is produced, using a fuel such as glucose

Define ventilation

The process of inhaling and exhaling air into and out of the lungs

For efficient diffusion, an exchange surface has...

Large surface area, a short didstance for the gas to diffuse, a large difference in the concentration of gas on opposite sides of the surface

3 ways insects are adapted for gas exchange

Large number of tracheoles so large surface area, tracheoles have thin walls so short diffusion distance, body muscles can pump air so maintains concentration gradient of O2 and CO2.

What is a spiracle?

An opening in the exoskeleton of an insect that connects to the tracheal system

What are the tracheae and tracheoles?

Tubes in the insect respiratory system that carry air to muscles

2 ways an insect is adapted to reduce water loss

Spiracles can be opened and closed using valves, tiny hairs around spiracles

What is the operculum?

Protects the gills

How are lamellae adapted?

Create large surface area and contain large network of blood capillaries

Define counter-current system

Blood and water flow in opposite directions, maintaining a steep concentration gradient of oxygen along the entire lengh of the capillary

5 key features of the alveoli

Alveolar wall cells are very thin and flattened, alveoli covered in network of blood capillaries, capillary walls are very thin and narrow, elastic fibres help to recoil the lings, continuous flow of blood and ventilation maintain conc gradient

Mechanism of inhalation

External intercostal muscles contract, internal intercostal muscles relax, ribs move up and out, diaphragm contracts and moves down, volume of thorax increases, pressure decreases, air moves in due to pressure difference

Mechanism of exhalation

External intercostal muscles relax, internal intercostal muscles contract, ribs move down and in, diaphragm relaxes and moves up, volume of thorax decreases, pressure increases, air moves out due to pressure difference

3 ways leaves are adapted for gas exchange

Stomata (pores) on under-side of leaf, air spaces in spongy mesophyll, thin tissue

How does a plant reduces water loss?

Waterproof waxy cuticle, guard cells control opening and closing of stomata, absorbs large amounts of water from the soil

Examples of xerophytes

Marram grass, cacti

5 general adaptations of xerophytes

Thick cutilce, small or needle-shaped leaves, few stomata, sunken stomata in pits, hairs around stomata

4 adaptations of cacti

Spines, large stem to store water, less stomata, shall or deep root system

4 adaptations of marram grass

Leaves can roll up, thick cuticle with no stomata, sunken stomata, many hairs

Ingestion

Food taken into the mouth

Digestion

Enzymes break down large insoluble molecules into smaller soluble ones

Absorption

The products of digestion are absorbed through the lining of the intestine

Egestion

Removal of faeces

Proteins hydrolysed into...

Amino acids

Carbohydrates hydrolysed into...

Simple sugars e.g. glucose

Fats hydrolysed into...

A mixture of fatty acids and glycerol

Carbohydrate digestion occurs in the...

Mouth and small intestine

Protein digestion occurs in the...

Stomach and small intestine

Fat digestion occurs in the...

Small intestine

Function of amylase

Hydrolyses starch to maltose

Function of maltase

Hydrolyses maltose to glucose

Enzymes found in membranes of epithelial cells in small intestine include...

Maltase, sucrase, lactase

Function of villi

Contain microvilli and increase surface area for absorption

Glucose absorption

Glucose and sodium ions transported into epithelial cell by facilitated diffusion using co-transporter protein. Sodium ions actively transported into blood to maintain conc gradient. Glucose moves into blood by facilitated diffusion.

Function of endopeptidases

Hydrolyse peptide bonds making protein into smaller chunks

Function of exopoeptidases

Hydrolyse near the ends of the polypeptide chains, producing dipeptides

Function of stomach acid

Low pH for optimum pH of endopeptidases and also kills pathogens

Function of dipeptidases

Found in membrane of epithelial cells of the small intestine where they hydrolyse dipeptides into amino acids

Function of sodium-potassium pump

Used to transport sodium ions out of the cell by active transport

Amino acid absoption

Amino acids and sodium ions transported into epithelial cell by facilitated diffusion using co-transporter protein. Sodium ions actively transported into blood to maintain conc gradient. Amino acids moves into blood by facilitated diffusion.

Reason for emulsification

Large fat globules broken down into small fat droplets by bile salts in bile

Reason for emulsification

Increases the surface area available for lipase enzymes to digest the lipids

Define micelle

Tiny droplets of monoglycerides, fatty acids, bile salts and phospholipids

Role of micelles in lipid absorption

Transport poorly soluble monoglycerides and long-chain fatty acids to the surface of the epithelial cells

Define chylomicron

These are water-soluble fat droplets containing triglcerides, cholesterol and phospholipids

How do chylomicrons enter circulation?

Via the lacteal

Define mass transport

The bulk movement of liquids or gases in one direction, usually through a system of tubes or vessels

Define plasma

The straw coloured liquid component of blood

5 adaptations of erythrocytes

Small size, flattened disc shape, thin central part, no organelles, contains haemoglobin

Structure of haemoglobin

4 polypeptde chains, each containing a heam group with Fe2+ ion at centre

Define tissue fluid

A fluid surrounding cells that is formed from blood plasma without large proteins

Role of heart in producing tissue fluid

Contraction of ventricles creates high hydrostatic pressure, forcing water out of capillaries

Define lymph capillary

A vessel that helps to drain tissue fluid and return plasma proteins to the blood via the lymphatic system

Cause of Kwashiokor/odedema

Diet low in protein, fewer plasma proteins in blood, water not reabsorbed, excess tissue fluid causes swelling

Cause of elephantiasis

Lymph vessel blocked by parasitic worms, build up of tissue fluid causes swelling

Define oxyhaemoglobin

Complex formed when haemoglobin binds to oxygen

Cooperative binding

Oxygen binding to haemoglobin causes a conformational change, which allows subsequent oxygen molecules to bind more easily

Effect of increase in partial pressure of carbon dioxide on oxygen dissociation curve

Shifts to right

Function of coronary arteries

Supply the heart muscle cells with blood

Advantage of a double circulatory system

High pressure is maintained as blood is pumped twice per full cycle

Name of blood vessels entering and leaving the lungs

Pulmonary artery and vein

Name of blood vessels entering and leaving the kidneys

Renal artery and vein

Adaptations of arteries

Thick walls, many elastic fibres, smooth endothelium

Adaptations of veins

Thin walls, wider central lumen, less elastic fibres, contains valves

Structure of capillaries

Wall is one cell thick, huge network throughout body

Function of valves in the heart and veins

Prevent the backflow of blood

Define cardiac cycle

The sequence of events that make up one heart beat

Define the systemic cicruit

The part of the human circulatory system which transports blood away from the heart to the major organs of the body

Define the pulmonary circuit

The part of the human circulatory system which transports blood away from the heart to the lungs only

Position of heart valves during atrial systole

AV valves open, SL valves closed

Position of heart valves during ventricular systole

AV valves closed, SL valves open

Position of heart valves during dystole

AV valves closed, SL valves closed

Cardiac output =

Stroke volume x heart rate

How does fetal haemooglobin differ?

Higher affinity to oxygen

Why does fetal haemoglobin differ?

Allows fetal haemoglobin to become saturated with oxygen even when the mother's haemoglobin is not fully saturated

Cohesion-tension theory

The theory of intermolecular attraction between water molecules that explains the flow of water up a plant

Adaptations of the xylem

Dead, hollow cells; cell wall contains lignin; contain pits

Adaptations of the phloem

Perforated sieve plates; lack of organelles; supported by companion cells

Define transpiration

The evaporation of water vapour, mainly through the stomata in the surface of a leaf

Define translocation

The movement of organic substances through the phloem of plants from a source to a sink

Define osmosis

The passive movement of water from an area of high water potential to low water potental across a partially permeable membrane

Define the transpiration stream

The flow of water through a plant, from the roots to the leaves, via the xylem vessels

How does water enter the root cells?

Root cells actively transport mineral ions into the cell which lowers the water potential. Water then moves in by osmosis.

Define source

Where organic compounds are synthesised

Define sink

Where organic compounds are delivered to for use or storage

What does a potometer measure?

The rate of transpiration

Key things to remember when setting up a potometer

Set up under water; use vaseline to prevent air entering the system; cut the shoot at a diaganol

Mass-flow hypothesis

The flow of sap from source to sink as a result of changes in hydrostatic pressure

3 pieces of evidence for the mass-flow hypothesis

Phloem sap oozes out under pressure; sucrose concentrations differ at sinks and sources