B2.2: The Challenges Of Size Flashcards
Why do multicellular organisms need exchange surfaces?
They have a low surface area to volume ratio, making diffusion inefficient without specialized surfaces.
What substances are transported in and out of organisms?
Oxygen, carbon dioxide, water, dissolved food molecules, mineral ions, and urea.
What is the human circulatory system?
A double circulatory system
How are arteries, veins, and capillaries adapted to their functions?
Arteries: Thick walls, narrow lumen, high pressure.
Veins: Thin walls, large lumen, valves.
Capillaries: One-cell-thick walls for diffusion.
How are red blood cells adapted for transport?
Biconcave shape (increased surface area).
- No nucleus (more room for hemoglobin).
- Hemoglobin binds oxygen
How does the plasma function in transport?
Plasma carries nutrients, hormones, waste and heat
How do plants absorb water and minerals?
Root hair cells: Large surface area, thin walls, active transport for minerals.
- Xylem: Transports water.
- Phloem: Transports sugars (translocation).
What is the function of the heart?
Pumps blood around the body in a double circulatory system
What does the right ventricle do?
Pumps blood to the lungs for oxygenation
What does the left ventricle do?
Pumps oxygenated blood around the body
Why is the left ventricle thicker?
It needs force to pump blood around the body
What is the role of the pacemaker?
Controls the heart rate using electrical impulses
What are coronary arteries?
Blood vessels supplying oxygen to the heart muscle
What is the function of heart valves?
Prevents backflow of blood
What do arteries do?
Carry blood away from the heart
How are the arties adapted?
Thick muscular walls to handle high pressure
What do veins do?
Carry blood to the heart
How are the veins adapted?
Large lumen
Valves to prevent backflow
What do capillaries do?
Connect arteries and veins, enabling diffusion
How are capillaries adapted?
One cell thick for easy diffusion
What is plasma?
Yellow fluid transporting substances in the blood
What does plasma transport?
CO2
Hormones
Waste
Nutrients
What do red blood cells do?
Carry oxygen using haemoglobin
How are red blood cells adapted?
No nucleus
Large surface area
Flexible
What do white blood cells do?
Fight infection
Phagocytes
Lymphocytes
What do platelets do?
Helps blood clotting
Why do large organisms need transport systems?
Diffusion alone is too slow
What happens when the surface area to volume ratio decreases?
Diffusion becomes less effective
Why is oxygen needed?
For respiration
What is carbon dioxide?
A waste product of respiration
Why is water important?
For normal cell function
Why are dissolved food molecules needed?
For energy and growth
Why are minerals transported?
To build new biomass
What is urea?
A waste product removed by the kidneys
What is the waxy cuticle?
A layer that reduces water loss from leaves
What are guard cells and stomata?
Structures controlling gas exchange
What do palisade cells do?
Carry out most photosynthesis
How are palisade cells adapted?
Packed with chloroplasts near the surface
What is the function of spongy mesophyll?
Allows gas exchange in the leaf
What does xylem transport?
Water and minerals from roots to leaves
How is xylem adapted?
Hollow tubes strengthened by lignin
What does phloem transport?
Sugars from leaves to the rest of the plant
What is translocation?
Movement of sugars in phloem
What does meristem tissue do?
Produces new cells for growth
Where is meristem tissue found?
In root and shoot tips
What is transpiraton?
The movement of water through a plant and its evaporation
What is the function of transpiration?
Helps pull water up through the plant
What factor affect transpiration rate?
Temperature
Humidity
Wind
Light
How can transpiration be measured?
Using a potometer
What do root hair cells do?
Absorb water and minerals
How are root hair cells adapted?
Large surface area for absorption
How does the size of an organism correlate to its surface area to volume ratio?
Larger organism, lower SA to volume ratio
What does the efficiency of gas excange depend on?
The efficiency of gas exchange depends on the surface area to volume ratio?
What may lungs contain to maximise diffusion rate?
Alveoli - increase the lungs surface area
What are adaptations of the alveoli for efficient gas exchange?
Very thin alveolus walls - shorter diffusion distance, easier
Spherical shape - large SA for diffusion
What does the small intestine contain to maximise diffusion rate?
Fingerlike villi, there may even be microscopic villi on the villi
What respiratory gases does blood transport?
O2
CO2
What are the 2 types of blood?
Oxygenated - high in O2
Deoxygenated - high in CO2
Wht type of blood does the right side of the circulatory system transport?
Deoxygenated
Wht type of blood does the left side of the circulatory system transport?
Oxygenated
What are the main components of the double circulatory system?
Heart
Arteries
Veins
Capillaries
What are the main components of blood?
Red blood cells
White blood cells
Platelets
Plasma
What is the role of the plasma in the blood?
The liquid part of the blood that carries everything but oxygen
What is the role of the platelets in the blood?
Clot blood when cut
What is the role of the RBC in the blood?
Carry oxygen from our lungs to the body tissues
Contain a pigment protein called haemoglobin
What is the role of the WBC in the blood?
Defence against pathogens
How much of our blood does RBC make up?
Half of the blood
What are adaptations of RBC?
No nucleus - more space for haemoglobin and oxygen
Shaped as a biconcave disk - more SA for oxygen
Packed of haemoglobin - protein binds to oxygen to form oxyhaemoglobin
How much of our blood does WBC make up?
Less tan 1%
Do white blood cells contain a nucleus?
Yes
Do platelets have a nucleus?
No
What do platelets do in the blood when there’s no cut?
They just float around
How do the platelets act as clotting?
Rush to the wound and act like glue, covering the hole
Stops blood pouring out and also prevent microorganisms entering
How much of the blood does plasma take up?
Half of blood volume
How much of the blood do platelets take up?
Small fragment of cells
What is the colour of plasma?
Pale straw colour
What does plasma do to the blood?
Makes watery
What does plasma carry apart from RBC WBC and platelets?
Glucose
Amino acids
Waste products
Hormones
Proteins
Anti-bodies - memory cells
Anti-toxins
What is the correct blood flow direction?
Body —> vena cava —> right atrium —> right ventricle —> pulmonary artery —> lungs —> pulmonary vein —> left atrium —> left ventricle —> aorta —> body
What are valves?
Ensure blood flowing in the correct direction and not flowing backwards
Where are pacemakers located?
Right atrium
What pressure do arteries carry blood at?
High pressures away from the heart
What is the texture like of arteries?
Strong and elastic
Thick layer of muscle and elastic tissue
What blood vessel gives the heart blood?
Coronary arteries
What do veins transport?
Deoxygenated blood
At what pressure do veins transport blood?
Low bp
What are features of veins?
Thin walls
Large lumen
Small layers of elastic and strong muscles
Walls do not need to be very strong
Valves
What are valves?
Prevent blood from flowing backwards
What is the size of capillaries?
Very small
Single cell thick
What are capillaries?
Exchange substances between the cells
Giving useful nutrients and oxygen and taking away waste products (CO2)
What is the blood pressure like in capillaries?
Low BP
What is the formula for the rate of blood flow?
Blood flow / time
How many layers do alveoli have?
One layer of very thin cell walls
Features of alveoli
Very moist walls
Allows gases to dissolve (increases diffusion rate)
What are the top 2 chambers of the heart called?
Atria
What are the bottom 2 chambers of the heart called?
Ventricles
How are the different chambers of the heart separated?
Through valves
What muscle is heart made up of?
Cardiac muscle
What are features of the cardiac muscle?
Contract without nerve stimulation
Never tire
Many cells contract together to form a heartbeat
Where does the aorta transport blood to?
Head and body
Where does the vena cava transport blood from?
Head and body
What are the 2 transport systems in plants?
Xylem
Phloem
Which direction does the xylem transport water and minerals?
From the roots UPWARDS to the plant stem and into the leaves by osmosis
How are mineral ions taken into the plant?
Active transport
Which direction does the phloem transport dissolved sugars?
Sugars produced during photosynthesis from leaves to other areas of the plant - translocation
What are sugars used for during translocation?
- growing parts of the plant for immediate use
- energy store
- storage tissue in roots
What is the structure like of xylem?
Made from dead xylem cells
Continuous hollow tube
Thick walls stiffened with lignin
Impermeable cell walls
What direction is the water and minerals in xylem structures?
One way only
What is the structure like of phloem?
Made of living cells
Sieve plates formed, not continuous, small holes in end walls allowing dissolved sugars to passs through
Cell walls are permeable
Which direction do sugars and food molecules flow in phloem?
Two way flow
What are vascular bundles?
The transportation systems of a plant
Where are vascular bundles located?
Located on the outer edge of the stem and centre of the root
Provides plant strength to resist bending in the breeze
What is transpiration?
The loss of water from a plants leaves
What is the transpiration stream?
The constant flow of water from the roots, through the xylem and out of the leaves
How is exactly is water taken into the transpiration stream?
Water travels from one root hair cell to another until it reaches the centre of the root. Once it reaches the xylem, it can be transported all throughout the plant
What is the role of the stomata?
Water is lost through stomata
Carbon dioxide diffusing in during photosynthesis
What do guard cells control?
Opening and closing of stomata
Where is stomata found in the leaf?
Underside of the leaf
What does the loss of water do to the plant?
Reduces pressure in xylem vessel
How can uncontrolled water loss be prevented by the plant?
Upper surface of leaves is covered in a waxy waterproof layer - cuticle
What may happen to the plant when it loses water?
May cause wilt
Leaves collapse and droop
What happens when the stomata closes?
Stops photosynthesis
Prevents further water loss
What happens if a plant does not receive water?
May die
What is the formula for the rate of transpiration?
Distance (mm) / time (s)
What are the 3 factors affecting transpiration?
Humidity
Light intensity
Temperature
How does humidity affect transpiration?
More humidity, less transpiration
(Water in the air)
How does light intensity effect rate of transpiration?
Brigter light, greater transpiration rate
Stomata open - water lost until all stomata open (plateaus)
How does temperature effect rate of transpiration?
Warmer, faster transpiration
Water evaporates more quickly
What does insulin do hen blood glucose levels are high?
Move glucose from our bloodstream into the body’s cells to make energy
