Bio Paper 1 6 Markers

Question 1

Compare the structure and function of xylem tissue and phloem tissue.

Answer 1

Structure
* xylem is made of dead cells
and
phloem is made of living cells
* phloem cells have pores in their end walls
and
xylem cells do not have pores in their end walls
* xylem is hollow or xylem does not contain cytoplasm
and
phloem contains cytoplasm
* xylem contains lignin
and
phloem does not (contain lignin)
* both made of cells
* both tubular
Function
* xylem transports water / mineral ions
and
phloem transports (dissolved) sugars
* xylem is involved in transpiration
and
phloem is involved in translocation
* xylem transports unidirectionally
and
phloem transports bidirectionally
* both transport liquids / substances throughout the stem / leaves
/ roots / plan

Question 2

Compare the structure of a red blood cell with the structure of a plant cell.

Answer 2

Differences:
* red blood cell has no nucleus or plant cell has a nucleus
* red blood cell has no cell wall or plant cell has a cell wall
* red blood cell is a biconcave disc or there are many different
shapes of plant cell
* red blood cell contains haemoglobin or plant cells do not
contain haemoglobin
* red blood cells do not contain chlorophyll or plant cells (may)
contain chlorophyll
* red blood cell has no chloroplasts or plant cell has chloroplasts
* red blood cell has no (permanent) vacuole or plant cell has
(permanent) vacuole
* red blood cells are (much) smaller than plant cells
Similarities:
both have:
* cytoplasm
* cell membrane
* pigments (although they are different)

Question 3

Evaluate the use of stem cells from a patient’s own bone marrow instead of
stem cells from an embryo.
Give a conclusion to your answer.

Answer 3

embryos advantages
* can create many embryos in a lab
* painless technique
* can treat many diseases / stem cells are pluripotent / can become
any type of cell (whereas bone marrow can treat a limited number)
embryos disadvantages
* harm / death to embryo
* embryo rights / embryo cannot consent
* unreliable technique / may not work
bone marrow advantages
* no ethical issues / patient can give permission
* can treat some diseases
* procedure is (relatively) safe / doesn’t kill donor
* tried and tested / reliable technique
* patients recover quickly from procedure
bone marrow disadvantages
* risk of infection from procedure
* can only treat a few diseases
* procedure can be painful
both procedures advantage
can treat the disease / problem
both procedures disadvantages
* risk of transfer of viral infection
* some stem cells can grow out of control /
become cancerouS

Question 4

Explain how the human lungs are adapted for efficient exchange of gases
by diffusion.

Answer 4

• (many) alveoli
• provide a large(r) surface area (: volume)
• capillaries are thin
  or alveoli / capillary walls are thin or one cell thick
  or capillaries are close to the alveoli
• which provides short diffusion path (for oxygen / carbon
  dioxide)
• breathing (mechanism) moves air in and out or lungs are
  ventilated
• to bring in (fresh) oxygen
• to remove carbon dioxide
• to maintain a concentration / diffusion gradient
• large capillary network (around alveoli) or good blood supply
• to remove oxygen(ated blood) quickly
• to bring carbon dioxide to the lungs quickly
• to maintain a concentration / diffusion gradienT

Question 5

Some types of cancer can cause the numbers of blood components in a
person’s body to fall to a dangerously low level.
A person with one of these types of cancer may experience symptoms
such as:
* tiredness
* frequent infections
* bleeding that will not stop after the skin is cut.
Explain how a very low number of blood components in the body can
cause these symptoms.

Answer 5

Tiredness
* fewer red blood cells
* so less haemoglobin
* so less oxygen transported around the blood
* so less (aerobic) respiration can take place
* so more anaerobic respiration takes place
* less energy released for metabolic processes or less energy
released so organs cannot function as well
* lactic acid produced (during anaerobic respiration) causes
muscle fatigue
Frequent infections
* fewer white blood cells / phagocytes / lymphocytes
* so fewer antibodies produced or less phagocytosis
* so fewer pathogens / bacteria / viruses killed
Bleeding
* fewer platelets
* so blood does not clot as easily

Question 6

Explain the ways the man’s body has responded to the exercise.

Answer 6

• heart rate increased
  ○ to increase blood flowing to muscles / lungs
  ○ to provide more oxygen (to muscles)
  ○ to provide more glucose (to muscles)
  ○ to remove carbon dioxide more quickly (from the
  muscles / blood)
  ○ to remove lactic acid more quickly (from the muscles)
• breathing rate increased
  ○ supplies more oxygen / air to lungs
  ○ so more oxygen to blood
  ○ more carbon dioxide removed
• more oxygen to muscles
  ○ needed for (increased) respiration
  ○ to release / provide energy
  ○ for muscle contraction
• anaerobic respiration occurs
  ○ due to lack of oxygen
  ○ which causes a build-up of lactic acid
  ○ oxygen debt
  ○ muscle fatigue / pain

Question 7

Explain how the villi and the alveoli are adapted to absorb molecules into
the bloodstream

Answer 7

S = structural F = functional
* (S) both have a large surface area
* (S) villi have many microvilli
* (S) alveolar walls are not flat / are folded
* (F) to maximise diffusion (of gases) / absorption of (food) molecules
* (S) both have many capillaries / good blood supply / capillaries near
the surface
* (F) to maintain concentration / diffusion gradient
* (S) both have thin walls / walls that are one cell thick / one cell thick
surface
* (F) to provide a short diffusion distance (for molecules to travel)
* (S) villi have many mitochondria
* (F) to provide energy for active transport (of food molecules)
* (S) cells of the villi have microvilli / more projection
* (F) to further increase the surface area / increase the number of
proteins in the membrane / to allow more active transport to take
place

Question 8

Describe how the human body:
* prevents pathogens from entering
* defends itself against pathogens inside the body.

Answer 8

prevents pathogens from entering
skin
* tough / dry / dead outer layer
* skin acts as a barrier
* sebum / oil on (surface of) skin
* sebum / oil repels pathogens
* scabs form over cuts or scabs form a barrier
* platelets are involved in forming clots / scab
stomach
* contains (hydrochloric) acid
* (HCl) kills bacteria
* in food or in swallowed mucus
eyes
* produce tears
* contains enzymes to kill bacteria
* tears are antiseptic
breathing system
* trachea / bronchi / nose produce mucus
* mucus is sticky
* (mucus) traps bacteria
* (mucus) carried away by cilia
defends itself against pathogens inside the body
* immune system / white blood cells (WBCs)
* WBCs engulf pathogens
* antitoxins are produced
* (antitoxins) neutralise toxins / poisons (produced by pathogen)
* antibodies are produced
* (antibodies) help destroy pathogens
* memory cells (are formed)
* (memory cells give a) more rapid response if pathogen
re-enter

Question 9

In 2014 the Ebola virus killed almost 8000 people in Africa.
Drug companies have developed a new drug to treat Ebola.
Explain what testing must be done before this new drug can be used to
treat people.