Download B3 questions - Revise 4 Science

What are the differences between diffusion and
active transport?
Explain how active transport works to move
substances across cell membranes (4 points)
Explain why active transport is needed in our guts
State two examples of active transport
Define osmosis
State the two main functions of sports drinks
Explain the five steps involved in breathing in
Explain why larger organisms require specialised
exchange surfaces, but very small organisms do not
Describe and explain the structure of a villi that
enables it to act as a specialised exchange surface
How does inhaled and exhaled air differ?
State three examples of specialised exchange
surfaces in animals
State two examples of specialised exchange surfaces
in plants and describe what they exchange
State four reasons for why plants need water

Active transport requires energy carried by
ATP, diffusion does not
 Active transport requires special carrier
proteins on the cell membrane, and diffusion
doesn’t
 Active transport moves substances from low
to high concentration, diffusion is from high
to low concentration
1. Chemical joins to carrier protein
2. Energy from ATP changes carrier protein
shape
3. This pushes chemical through
4. Carrier protein returns to normal shape
By diffusion alone, sugar will reach equilibrium /
equal concentrations between gut and cells
Active transport needed to force molecules against
their concentration gradient
Mineral uptake in root hair cells
Absorption of glucose in the gut
The movement of water…
Through a partially-permeable membrane…
From a low to high concentration of SOLUTES
1. Replace water and ions lost through sweating
2. Replace sugars that are used in respiration
 Intercostal muscles CONTRACT
 Ribs move UP and OUT
 Diaphragm contracts and flattens
 Volume in the thorax increases and the
pressure decreases
 This causes air to flow in
Large organisms have a small surface area to
volume ratio
Simple diffusion wouldn’t be enough to allow
substances to get to all cells
1. A good blood supply to maintain a steep
concentration gradient
2. A lacteal to dissolve and transport fats
3. Thin walls (one cell thick) to decrease the
diffusion distance
Inhaled air has 21% oxygen, exhaled air has 17%
oxygen
Inhaled air has 0.04% CO2, exhaled air has 4% CO2
Alveoli (lungs), Gills of fish, Villi (lungs)
Roots – active transport of ions, osmosis for water
Leaves – gas exchange (CO2 and O2)
1. It’s a reactant in photosynthesis
2. Cooling to maintain enzyme optimum
temperature
3. Maintains turgour pressure of cells
4. Transports substances (e.g. minerals and
sugars)
Describe the two forces involved in ensuring water is Cohesion: water molecules attract each other
pulled up through the xylem during transpiration
Adhesion: water is attracted to the walls of xylem
What part of the leaf allows water to leave, and how Stomata
do they work?
 If there is lots of water, guard cells fill to
become turgid – this opens the stoma and
water can leave
 If there isn’t much water, guard cells lose
water and become flaccid
Describe and explain how humidity affects
As humidity increases, transpiration decreases
transpiration
More humidity means there is more water in the air,
decreasing the concentration gradient
Describe and explain how wind speed affects
As wind speed increases, transpiration increases,
transpiration
but then plateaus
Higher wind speed means more water in the air is
moved away, increasing the concentration gradient.
Once all the water is moved away, no more increase
in transpiration can occur.
Describe and explain how temperature affects
As temperature increases, transpiration increases
transpiration
Higher temperatures mean water gains energy and
evaporates at a faster rate
Describe and explain how light intensity affects
As light intensity increases, transpiration increases,
transpiration
but then plateaus
More light means more stomata open, increasing
transpiration. However once all stomata are open,
no further increase in transpiration can occur.
What are the upper chambers in the heart called?
Atria (singular: atrium)
What is the lower chamber of the heart that pumps
a) Left ventricle
blood to:
b) Right ventricle
a) the body?
b) the lungs?
What is the wall that separates the left and right
Septum
sides of the heart called?
Which blood vessel takes blood:
a) Pulmonary artery
a) From the heart to lungs?
b) Pulmonary vein
b) From lungs to heart?
c) Aorta
c) From heart to body?
d) Vena cava
d) From body to heart?
What are the valves that separate atria and
Atrioventricular (AV) valves
ventricles called, and what is their function?
- They prevent backflow of blood
What are FIVE differences between arteries and
- Veins have valves, arteries don’t
veins?
- Veins have LARGE lumens, arteries have
SMALL lumens
- Arteries have thick muscular walls, arteries
have thin walls
- Arteries have a higher pressure than veins
- Arteries are have many elastic fibres, veins
do not
When are stents used, and how do they work?
They are used to widen blocked arteries
Balloon inside the stent is inflated, then burst and
removed – this creates space in the artery
What are artificial hearts made of and why is this
Polymers and titanium
important?
- Very smooth to avoid friction and clots
- No antigens so body can’t reject them
What two ways can damaged heart valves be
treated?
How is blood classified?
State four components of blood and describe their
functions
Describe where the blood transports the following
components from and to:
a) Carbon dioxide
b) Assimilates (e.g. sugars) from digestion
c) Urea
Explain how red blood cells are adapted to carry out
their function
What compound is created when oxygen binds to
the oxygen-carrying compound of red blood cells?
What does xylem transport, and where?
What does phloem transport, and where?
What is transpiration?
1. How is carbon dioxide produced?
2. Why does it need to be removed?
3. How is it removed?
1. How is urea produced?
2. Why does it need to be removed?
3. How is it removed?
Explain the negative effects of water or ion
imbalance on the body
Explain how the kidneys regulate water and ion
concentration
What happens to sugar in the blood as it passes
through the kidneys?
Describe two treatments for people with kidney
failure
Describe the risks of kidney transplants
1. Use animal valves
2. Synthetic valves can be used
 Both have no risk of rejection
It’s a tissue (the only liquid tissue in the body)
Plasma – carries proteins, CO2 and hormones
Red blood cells – carries oxygen
White blood cells – destroys pathogens
Platelets – cell fragments that form clots
a) From respiring tissues / muscles to the lungs
b) From the gut to respiring tissues/muscles
c) From the liver to the kidneys
Biconcave shape and no nucleus – large surface area
Haemoglobin to carry oxygen
Oxyhaemoglobin
Water and mineral ions UP the plant
Dissolves sugars from SOURCE (e.g. leaves) to SINK
(e.g. roots)
The movement of water from the roots, through the
xylem and then out of the leaves by evaporation
1. It’s a waste product of respiration
2. It dissolves to lower pH of blood, and causes
asphyxiation
3. It diffuses from blood through the alveoli and
leaves with air that is breathed out
1. Ammonia formed by breakdown of amino
acids – it reacts with CO2 in liver to form urea
2. Ammona/urea are alkaline and increase pH
3. Urea travels in blood to kidneys, and is
filtered and dissolved in water before being
excreted
If solute concentration in blood is too high, water
moves OUT of cells causing metabolism to cease
If solute concentration in blood is too low, water
moves INTO cells causing them to swell and possibly
burst
Water and ions pass into the NEPHRON
Some water and ions are selectively reabsorbed as
needed.
It first enters the nephron by filtration…
But ALL sugar is reabsorbed back into the blood
stream
1. Frequent dialysis – patient blood passes
through a partially permeable membrane to
extract urea, and salts are removed or added
to blood as needed
2. Kidney transplants
Donor kidney could be rejected – the immune
system may recognise antigens as a threat and
produce antibodies to destroy it
Explain two methods that are used to reduce the
impact or risk of kidney rejection
Describe two ways our body monitors temperature
Explain two ways that the body changes to cool
down if temperature is too high
Explain two ways that the body changes to prevent
heat loss if the temperature is too low
Which organ monitors and controls blood glucose
concentration?
Which hormone increases the amount of glucose in
the blood?
Which hormone decreases the amount of glucose in
the blood?
Explain the steps involved in decreasing glucose
concentration in the blood after eating
Explain the steps involved in increasing glucose
concentration in the blood after fasting
Describe what causes Type 1 diabetes
What four things should Type 1 diabetes sufferers
do as part of their treatment?
State four medical risks for people with uncontrolled
Type 1 diabetes
State four reasons for the human population
explosion
1. Tissue typing – kidneys from donors are
matched with a patient’s tissue type
2. Immunosuppressant drugs to avoid damage
by immune system
The hypothalamus monitors blood temperature
The skin monitors external temperature
1. Vasodilation – arterioles near the skin
widen…
… causing blood to pass nearer to skin…
… leading to heat loss by radiation
2. Sweating – skin heat transfers energy to
water. As it evaporates, mean energy of
remaining water decreases
1. Vasoconstriction – arterioles narrow…
… causing blood to flow deeper in the body…
… leading to less radiation
2. Shivering – muscles contract involuntarily
leading to heat produced by respiration
The pancreas
Glucagon
Insulin
1. Pancreas detects glucose is too high
2. Insulin is released into bloodstream
3. Insulin reaches target cells in liver/muscles,
causing glucose to be stored as glycogen
4. Insulin causes all cells to increase respiration
1. Pancreas detects glucose is too low
2. Glucagon is released into bloodstream
3. Glucagon reaches target cells in
liver/muscles
4. Glucagon causes glycogen to be broken into
glucose which enters the bloodstream
 Immune system recognises antigens on
pancreas cells as a threat and attacks them
 Pancreas can’t produce enough insulin
 Increase complex (starchy) carbohydrates
and reduce simple carbohydrates
 Exercise regularly
 Monitor blood glucose and inject insulin at
mealtimes
 Avoid alcohol
 Retinal damage  blindness
 Ulcers in feet  gangrene / loss of toes
 Increased risk of stroke
 Increased risk of heart attack
 Improved diets  food contains more
nutrients and minerals
 Improved sanitation / hygiene  lower
spread of disease
 Medical advances (give a specific example)




Lower infant mortality rate
State four problems caused by unsustainable growth
World food shortages
in the human population
Increase in pollution
Unsustainable use of resources (e.g. fossil
fuels)
 Land used for farming and building
1. Describe why fertilisers are used
1. They provide nitrates that help plants grow
2. Explain the environmental harm they cause
quickly
through eutrophication
2. Nitrates leach into water sources causing water
plants / algae to grow. This reduces oxygen so
animals die and rot, producing CO2.
Explain how burning fossil fuels leads to acid rain
Sulfur dioxide dissolves in rainwater to make
sulphuric acid
Nitrogen dioxide dissolve to make nitric acid
Carobn dioxide dissolves to make carbonic acid
Explain how acid rain causes environmental harm
 Damages plant leaves
 Acidifies lakes
 Changes mineral availability in soil
 Causes bronchitis
Explain two problems associated with allowing
 Bacteria (e.g. cholera and typhoid) may be
untreated sewage into waterways
present causing illness
 Sewage contains nitrates causing
eutrophication
Explain how toxic chemicals lead to bioaccumulation Toxins leach into waterways
These build up in higher quantities in the food chain,
as animals at higher trophic levels consume many
organisms
Explain the causes and effects of global dimming
Incomplete combustion releases smoke /
particulates into the atmosphere
These can block the Sun’s rays, causing dimming
Lower light intensity means less photosynthesis
occurs.
Describe how methane is produced agriculturally
Methane produced by rearing cattle and growing
and how it causes environmental problems
rice crops.
Methane is a powerful greenhouse gas that traps
and re-emits infra-red light. This leads to global
warming, causing climate change.
Explain how CFCs affect the environment
CFCs break down the ozone layer.
This layer normally absorbs ultraviolet light.
If the ozone layer is depleted, this means the rates
of skin cancer increase
Explain how detergents affect waterways
Detergents kill microbes. This means microbes
cannot rot dead plants and animals, affecting the
food chain.
Describe three ways that deforestation leads to an
 Slashing and burning trees produces CO2 by
increase in CO2
combustion
Left-over tree stumps rot, decomposers

produce CO2
 Fewer trees mean less photosynthesis so less
CO2 absorbed
Explain what peat is, and how it leads to CO2
Peat is made of preserved sphagnum moss.
production
If used as compost, it decomposes to produce CO2
Explain four biological effects of global warming
Explain how carbon dioxide can be sequestered in
oceans
Explain three ways that humans have ensured our
farming food chains are efficient
Describe and explain two methods of preventing
overfishing
Which fungus is used to make protein-rich food, and
by which process?
State three common examples of biofuels
State three advantages of using biofuels
State and describe the disadvantage of using
biofuels
How is biogas made?
State three uses of biogas
State the difference in production between biogas
and bioethanol

Reduced biodiversity – therefore more
extinctions as habitats destroyed
 Ice caps melting – leads to sea levels rising
 Climate change – leads to storms, droughts
that affect organisms
 Migration patterns affected – animals winter
in different countries
1. Carbon dioxide dissolves in water to form
carbonic acid
2. Phytoplankton absorb CO2 through
photosynthesis
 The number of stages (trophic levels) are
reduced, meaning less energy is lost
 Animals are kept warm, reducing
homeostasis energy loss
 Battery farmed animals can’t move much,
reducing energy loss from respiration
Large net sizes – prevents small fish being caught, so
they can breed and restock oceans
Fishing quotas – limiting how many, or which types,
of fish allows them to restock
Fusarium, used in fermentation
Wood, biogas, bioethanol (alcohol)
Reduced fossil fuel consumption
No net increase in CO2
No particulates are produced
Habitat loss due to large areas of land used for crops
This leads to extinction of species
 Fermentation of carbohydrates from plant
material and sewage…
 by bacteria…
 at a temperature between 32-35OC
 to produce methane and other gases
 Vehicle fuel
 Generating electricity
 Central heating systems
Biogas requires bacteria for fermentation,
bioethanol requires yeast
What is bioethanol called when it is mixed with
Gasohol
petrol?
Explain why Brazil uses gasohol (bioethanol and fuel)
 They don’t have natural oil reserves
in their cars
 They have plenty of sugar cane
 They have plenty of land
 Therefore they can grow and ferment sugar
cane to produce bioethanol