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• To function properly, organisms must exchange substances with their environment, like food and waste.

Unicellular Organisms

• Exchange happens via diffusion, osmosis, and active transport across the cell membrane.
• Amoebas do not need specialized exchange surfaces or transport systems due to their large surface area to volume ratio, sufficient for their needs.

Multicellular Organisms

• Multicellular organisms, like humans, have bodies composed of many cells.
• The distance from the surface to the center is too long for diffusion alone because these organisms have multiple cell layers.
• Larger organisms need transport systems because diffusion to all cells would be too slow.
• The circulatory system carries essential substances in the blood in animals.
• The vascular system transports substances in plants.
• The xylem moves water and minerals from roots to shoots.
• The phloem distributes sugars and amino acids throughout the plant.

Role of the Xylem & Phloem

• The xylem and phloem make up the transport system of vascular plants.
• The xylem transports water and mineral ions from the roots to other parts of the plant.
• Xylem has a hollow tube of dead cells, reinforced by lignin, which provides a route for the column of water to move through the plant by transpiration.
• The phloem transports sucrose and amino acids from where they are produced or stored to where they are needed.
• Sucrose and amino acids are produced in the leaves while plants photosynthesise, so they are transported from the leaves to other parts of the plant. The phloem is formed from living cells forming a tube with small holes through which substances can move.

Root Hair Cells

• Root hairs are single-celled extensions of epidermis cells in the root that grow between soil particles and absorb water and minerals from the soil.
• They are adapted for the efficient uptake of water (by osmosis) and mineral ions (by active transport).
• The cells contain mitochondria which release energy for active transport.
• Root hairs increase the surface area of plant roots, increasing the rate at which water and minerals can be taken up.
• Roots hair cells take up mineral ions from the soil by active transport.
• The water concentration of the cell cytoplasm is reduced due to the presence of mineral ions.
• Water moves into the root hair cell by osmosis.
• The structure of a root maximize absorption of water by osmosis and mineral ions by active transport.
• Water moves, by osmosis, into the root hair cells, through the root cortex and into the xylem vessels.
• The water gets into the xylem, it is carried up to the leaves where it enters mesophyll cells.
• The pathway is: root hair cell → root cortex cells → xylem → leaf mesophyll cells.

Transpiration

• Transpiration is water vapor loss from the aerial parts of the plant like leaves, stem, and flowers.
• Water loss occurs through water evaporation at the surfaces of the spongy mesophyll cells followed by diffusion of water vapor through the stomata
• Transpiration transports mineral ions.
• Transpiration provides water to keep cells turgid for structure and water to leaf cells for photosynthesis.
• Transpiration also has the function of keeping the leaves cool as heat energy is removed from the leaves when water evaporates.

Factors Affecting Transpiration

• Several environmental conditions affect the rate of transpiration, including:

  • Air movement
  • Humidity
  • Temperature
  • Light intensity

• When wind speed increases, transpiration rate increases because water molecules diffuse out of stomata quickly, maintaining a concentration gradient.

• When temperatures increase, transpiration rate increases because water vapor molecules have more kinetic energy and move faster.

• When humidity increases, transpiration decreases because humid air reduces the diffusion gradient.

• When light intensity increases, transpiration increases because stomata open for gas exchange related to photosynthesis.

Factors Affecting Transpiration: Practical Investigation

• A potometer measures the rate of transpiration.
• A mass potometer measures a change in mass of a plant as a measure of the amount of water that has evaporated from the leaves and stem
• A bubble potometer measures the uptake of water by a stem as a measure of the amount of water that is being lost by evaporation consequently pulling water up through the stem to replace it
• Environmental conditions, like temperature and humidity, affect the transpiration rate.

Examining the effect of light intensity on transpiration (bubble potometer)

• The following apparatus are needed to investigate the affect of light intensity on transpiration
  • Potometer
  • Timer
  • Lamp
  • Ruler
  • Plant
• Investigative steps:
  • Cut a shoot underwater.
  • Prevent air entering the xylem and place it in the tube.
  • Set up the apparatus. Ensure airtightness, using Vaseline.
  • Dry the leaves of the shoot, or results will be affected.
  • Allow a single air bubble to form and place the tube back into the water
  • Set up a lamp 10cm from the leaf.
  • Allow five minutes for the plant to adapt to its environment.
  • Mark and record the starting location of the air bubble.
  • Leave for 30 minutes.
  • Record the bubble's ending location.
  • Change the lamp's light intensity.
  • Reset the bubble.
  • Repeat the experiment.
• Calculate the transpiration rate, dividing distance by time; the further the bubble travels in the same period, the greater the rate.
• As light intensity increases, the rate of transpiration increases as the bubble moves a greater distance when the lamp was placed closer to the leaf
• Transpiration rate increases with light intensity because more stomata tend to be open in bright light in order to maximise photosynthesis
• The more stomata open, the more water lost resulting in stomatal pores

Blood Components

• Blood consists of red blood cells, white blood cells, platelets, and plasma.
• Plasma makes up over half of the blood volume.
• The remainder of the blood is mostly made up of red blood cells.
• White blood cells and platelets constitute what’s left.

Blood Composition

• 55% Plasma
• <1% White Blood Cells and Platelets
• 45% Red Blood Cells

Red Blood Cells

• Biconcave discs containing no nucleus to maximize the available capacity to carry the protein haemoglobin

White Blood cells

• Large cells. Different types have slightly different structures and functions.

Platelets

• Fragments of cells

Plasma Description

• The liquid is a clear, straw colored aqueous.
• Plasma's transport function is important to; including:
• Carbon dioxide - the waste product of respiration, dissolved in the plasma and transported from respiring cells to the lungs
• Digested food and mineral ions - dissolved particles absorbed from the small intestine and delivered to requiring cells around the body
• Urea - urea is a waste substance dissolved in the plasma and transported to the kidneys -Hormones - chemical messengers released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body - Heat energy - heat energy (created in respiration) is transferred to cooler parts of the body or to the skin where heat can be lost

Red Blood Cells

• Red blood cells are specialised cells which carry oxygen to respiring cells, adapted to function by:
  • Being full of haemoglobin, a protein for oxygen binding.
  • Having no nucleus, allowing more space for haemoglobin packing.
  • Exhibiting a biconcave disc shape that provides a large surface area to volume ratio increasing oxygen diffusion.

White Blood Cells

• White blood cells are part of the body's immune system, which helps defend the body against pathogenic microorganisms in two main types:
  • Phagocytes
  • Lymphocytes

Phagocytes

• They carry out phagocytosis by ingesting pathogens.
  • They use a sensitive cell surface membrane to detect chemicals from pathogenic cells.
  • Upon encountering a pathogenic cell, they engulf and release digestive enzymes to digest it in a nonspecific immune response.

Lymphocytes

• These produce antibodies, which are proteins with a shape specific to antigens on a pathogen's surface
• They produce a specific immune response, tailoring antibodies one type of antigen on a pathogen

Immunity

• The immune system is complex using white blood cells, with the function of preventing a reproductive infectious organism after it has entered the body, and destroying it.

• Immunity is when an organism has sufficient levels of antibodies to protect against a particular disease, so it experiences no symptoms from that disease.

• Steps of Infection and Immune Response:

1. Pathogen enters bloodstream, multiplies.
2. Release of toxins/infection of body cells (if bacteria), causing symptoms.
3. Phagocytes recognize/engulf invaders (non-specific).
4. Pathogen encounters a lymphocyte with matching antigens.
5. Lymphocyte produces specific antibodies.
6. Lymphocyte clones itself, producing more specific antibodies.
7. Antibodies eliminate pathogens.
8. Phagocytes engulf/destroy the pathogen debris.

Vaccines

• These are used to induce immunity by introducing harmless versions of a pathogen, which have reduced, eradicated many diseases worlwide:

  • SmallBox
  • Measles
  • Mumps
  • Tetanus

• A vaccine contains harmless versions of a pathogen created by:

  • Killing the pathogen
  • Making the pathogen unable to grow or divide (attenuated vaccine)
  • Using fragments of pathogens

• Vaccines are administered orally, nasally, or via an injection

1. In bloodstream: antigens in triggering an immune response.
2. Lymphocytes recognize antigens in triggering an immune response.
3. Activated lymphocytes create specific antibodies.
4. Vaccines produces memory cells.
5. Memory cells and antigens remain circulating in the blood stream.

• Future infections by vaccination lead to a much greater than first response due to the fast nature of infection.

Platelets and Blood Clotting

• Platelets are cell fragments used for blood clotting and forming scabs
  • When skin breaks, platelets stop bleeding.
  • Soluble fibrinogen proteins convert into insoluble fibrin with released chemicals.
    • An insoluble mesh forms which traps red blood cells forming a clot
  • The clot dries and develops a scab to; reducing blood loss and prevent bacteria entry as new skin grows.

Structure & Function of the Heart

• The heart is a double pump where:

• Oxygenated blood from the lungs enters the left side and pumps to the body in, systemic circuit.

  • The left ventricle has a thicker muscle wall as it must pump blood around the whole body.
    • Deoxygenated blood enters at the right and pumps to the lungs in the pulmonary circuit.

• A muscle wall called the Septum separates the two sides of the heart.

• Blood flow: Blood is pumped towards using veins and away using arteries where these coronary arteries supplies tissue.

• Valves prevent blood back-flowing to constant supply tissue.

• Deoxygenated blood goes from the vena cava into the right side.

• Atrium contracts and the tricuspid (atrioventricular) valve helps pull blood toward the tight ventricle.

• Ventricle contracts pushing blood through the semilunar to the artery.

• Blood goes to the lungs through the capillaries until, where gas exchange occurs.

  • Low pressure is prevented by damage capillaries.
  • The bicuspid forces blood into the left part of the heart
    • Ventricle forces blood out throughout the whole body Thicker muscle walls produce higher pressure preventing heart disease.

Heart Rate and Exercise

• Measured and affected by the number of times a heart beats in a minute (bpm), also affected by exercise adrenaline.
• Natural resting heart rate is affected by a group of right atrium called the pacemaker.
• Respiration occurs faster and increases the rate system by delivering oxygen and removing waste through nerves. After exercise, the body requires more adrenaline because breaking down this leads to greater light response.

Risk Factors for Coronary Heart Disease

• This is caused by supplying insufficient glucose via blood vessels, and increases fat intake.
• Depositions mainl formed by cholestrol caused by: -High saturated fat and cholesterol -Diet

Risks of Heart conditions

• Complete blockage of the artery means no aerobic respiration and leads to heart conditions.
• Increased weight leads to type 2 diabetes which further damages your blood vessels.
• Blood pressure increases force against the arteries.
• Carbon monoxide reduces oxygen.

Composition of Blood Vessels

• Blood vessels are made up of capillaries where smaller vessles branch from arterioles which branch into venules
• Each Vesse specifically adapted for this function using:

Arterial features

• High pressure flow.
• Thick musclar walls containing elastic fibres.
  • Help help pressure and help maintain this blood as it recoils back, also the narrows help in this process

Vein Features

• Low pressure is carried and have thin walls.
• Thinner walls
• Large lumen means reduced resistance.
• One way helps to maintain the flow if pressure isn't to high

Capillaries

• Leaky one cell thick features used to carry blood at slow speeds for tissues to both;
  • Oxygenated / Deoxygenated blood

Circulatory Structures

• The heart is made up of blood vessels where vessels carries oxygen and waste though:
  • Arterioles → Cappilaries → Venules All excess liquid leads to circulatory system

Organ Table

• Lungs: Pulmornary Vein, Artery
• Heart: Aorta, pulmonary artery
• Kidney: Renal Vein, Artery