edexcel biology unit 8

Describe the need to transport oxygen in an out of organisms

Transported into organisms and to cells for aerobic respiration, which generates energy (ATP).

Describe the need to transport carbon dioxide in and out of organisms

A waste product of respiration, it is transported out of cells and expelled from the body to prevent low pH

Describe the need to transport water in and out of organisms

Transported in for cellular functions, hydration, and maintaining blood volume/turgor pressure; transported out (via sweat, urine, or transpiration) for temperature,regulation and excretion

Describe the need to transport dissolved food molecules in and out organisms

Nutrients (glucose, amino acids) are absorbed from the gut and transported to cells for energy, growth, and repair.

Describe the need to transport mineral ions in and out of organisms

Needed for nerve impulses, muscle contraction, and maintaining water balance; transported into the body from food or soil.

Describe the need to transport urea in and out of organisms

A toxic waste byproduct of breakdown of excess amino acids in the liver, it must be transported to the kidneys to be excreted in urine.

Why are exchange surfaces and transport systems needed in multicellular organisms?

Low SA:V ratios, long diffusion distances, high metabolic rates, adaptations

Exchange surfaces and transport systems in multicellular organisms: low SA:V ratios

As organisms grow, their volume increases faster than their surface area. The outer surface becomes too small to supply the large volume of internal cells.

Exchange surfaces and transport systems in multicellular organisms: long diffusion distances

Cells deep within a large organism are too far from the surface for fast diffusion.

Exchange surfaces and transport systems in multicellular organisms: high metabolic rate

Active, large organisms need to quickly exchange large amounts of substances (oxygen, glucose, waste), requiring specialized, high-efficiency systems.

Exchange and surfaces transport systems in multicellular organisms: adaptations

Exchange surfaces are adapted by having large surface areas, thin membranes (short diffusion pathway), and efficient blood supplies to maintain concentration gradients

how are alveoli adapted for gas exchange?

diffusion between air in lungs, alveolar walls and blood in capillaries

Explain how alveoli are adapted for gas exchange: diffusion between air in the lungs

tiny, folded sacs provide a huge total surface area, allowing a large volume of gases to diffuse simultaneously

Explain how alveoli are adapted for gas exchange: alveolar walls

the alveolar walls are only one cell thick, minimizing the distance gases must travel.

Explain how alveoli are adapted for gas exchange: blood in capillaries

high blood flow brings deoxygenated blood to the lungs and carrying away oxygenated blood, which maintains a steep concentration gradient.

what are the factors affecting the rate of diffusion?

surface area, concentration gradient, diffusion distance

Describe the factors affecting the rate of diffusion: surface area

A larger surface area allows more particles to pass through at the same time, increasing the rate of diffusion.

Describe the factors affecting the rate of diffusion: concentration gradient

A steeper gradient causes a faster rate of diffusion because particles move more quickly from high to low concentration.

Describe the factors affecting the rate of diffusion: diffusion distance

A shorter distance results in a faster rate of diffusion, as particles reach their destination faster.

Describe the structure of blood

Red blood cells, white blood cells, plasma, platelets

Adaptations of red blood cells

Biconcave shape, no nucleus, small and flexible

Adaptations of red blood cells: biconcave shape

Increases surface area-to-volume ratio, maximizing oxygen diffusion efficiency.

Adaptations of red blood cells: no nucleus

Creates more internal space to carry hemoglobin, a protein that binds oxygen.

Adaptations of red blood cells: small and flexible

Allows them to pass through narrow capillaries.

Adaptations of white blood cells

Phagocytes and lymphocytes

Adaptations of white blood cells: phagocytes

Have lobed nuclei and can change shape to engulf and digest pathogens (phagocytosis).

Adaptations of white blood cells: lymphocytes

Produce specific antibodies to destroy pathogens and antitoxins to neutralizes toxins.

Explain how the structure of the blood is related to its function: plasma

Consists of 90% water, making it ideal for transporting dissolved substances like nutrients, urea, hormones, and heat throughout the body.

Explain how the structure of the blood is related to its function: platelets

tiny cell fragments which stick together to form a scab over wounds, stopping blood loss and preventing infection

What are the blood vessels?

Arteries, veins and capillaries

Function of blood vessels: arteries

Thick, elastic walls withstand high blood pressure and maintain blood flow from the heart.

Function of blood vessels: veins

Thin walls with valves prevent backflow, allowing low-pressure blood to return to the heart

Functions of blood vessels: capillaries

Walls are only one cell thick, allowing rapid diffusion of substances between blood and tissues.

what are the great vessels connected to the heart?

aorta, vena cava, pulmonary artery, pulmonary vein

aorta

carries oxygenated blood from the left ventricle, thick elastic walls to withstand and maintain high pressure to distribute blood throughout the body

vena cava

carries deoxygenated blood from the body to the right atrium;large lumen and thinner walls allow for lower-pressure blood return.

pulmonary artery

carries deoxygenated blood from the right ventricle to the lungs; muscular, elastic walls manage the pressure required to send blood to the nearby lungs.

pulmonary vein

returns oxygenated blood from the lungs to the left atrium; allows for lower pressure and carries blood back to the heart.

what are the structures of the heart?

valves, relative thickness of chambers and atria

valves

designed to open one way to ensure unidirectional blood flow, closing when pressure behind them forces them shut, preventing backflow during ventricular contraction.

relative thickness of chamber walls

left ventricle has a much thicker muscular wall than the right as it must generate higher pressure to pump blood to the entire body, whereas the right ventricle only pumps to the lungs

atria

the atria have thin walls as they only pump blood to the nearby ventricles

Describe cellular respiration

An exothermic reaction which occurs continuously in living cells to release energy for metabolic processes

What are the similarities between aerobic and anaerobic respiration?

Both processes produce energy to power cellular functions, both begin with glucose as the initial substrate and both are essential for the survival of organisms.

What are the differences between aerobic and anaerobic respiration?

Efficiency, oxygen use, byproducts and usage context

Differences between aerobic and anaerobic respiration: efficiency

Aerobic respiration is far more efficient, yielding up to 19 times more energy than anaerobic respiration.

Difference between aerobic and anaerobic respiration: oxygen use

Aerobic requires oxygen, whereas anaerobic operates without it.

Differences between aerobic and anaerobic respiration: by products

Aerobic produces water and carbon dioxide, while anaerobic produces lactic acid (which causes muscle fatigue) or ethanol (in fermentation).

Difference between aerobic and anaerobic respiration: usage context

Human bodies use aerobic for continuous, sustainable energy, switching to anaerobic only during intense exercise or low oxygen conditions.