Organisation and maintenance of the organism

Question 1

Living organisms are made of

Answer 1

cells

Question 2

Describe the differences in structure between typical animal and plant cells

Answer 2

Animals:
- Liver cell
- Nucleus in center
- Many small vacuoles
Plants:
- Palisade cell
- Nucleus is usually pushed to the side
- One large central vacuole
- Have cell walls and chloroplasts

Question 3

Relate the structures in the plant cell and in the animal to their functions

Answer 3

Animals and plants:
- Nucleus: contains genetic material which controls the activities of the cell
- Cytoplasm :most chemical processes take place here, controlled by enzymes
- Cell membrane: controls the movement of substances into and out of the cell
- Mitochondria :most energy is released by respiration here
Plants:
- Cell wall: strengthens the cell
- Chloroplasts: contain chlorophyll, which absorbs light energy for photosynthesis
- Permanent vacuole: filled with cell sap to help keep the cell turgid

Question 4

Structure and functions of:

ciliated cells, root hair cells, xylem vessels, muscle cells and red blood cells

Answer 4

Ciliated cells- in respiratory tract:
- Have cilia on their surfaces to move the mucus that traps dust and pathogens up to nose and the throat
Root hair cells - absorption:
- Have long extensions -> larger surface area to absorb water and ions from soil
Xylem vessels - conduction and support:
- They are hollow to allow water and minerals to pass through them with no resistance.
- Secondly they are strong and lignified to support the plant.
Muscle cells - contraction:
- Made of fibres and contractile filament to help contract
- Contains lots of mitochondria to supply the cell with energy
Red Blood Cells - transport:
- Have no nucleus to carry more o2 and co2
- Contains haemoglobin that carries oxygen
- Tiny so can travel through capillaries
- Biconcave disc shaped -> large surface area -> carry more oxygen

Question 5

Level of organisation. Define each term

Answer 5

Atom -> Molecule/Compound -> Organelle (nucleus) -> Cell -> Tissue -> Organ -> Organ System-> Organism
- Tissue :a group of cells with similar
structures, working together to perform a
shared function
- Organ: structure made up of a group of
tissues, working together to perform specific
functions
- Organ system: a group of organs with
related functions, working together to
perform body functions

Question 6

Define diffusion

Answer 6

the net movement of molecules from a region of their higher concentration to a region of their lower
concentration down a concentration gradient

Question 7

Define active transport

Answer 7

the movement of ions, in and out of a cell, through a cell membrane, from a region of their lower concentration to a region of their higher concentration, against the concentration gradient, using the energy released by respiration.

Question 8

Define osmosis

Answer 8

the diffusion of water molecules from a region of their higher concentration (dilute solution) to a region of their lower concentration (concentrated solution) through a partially permeable membrane.

Question 9

Factors that affect diffusion

Answer 9

o Distance (short -> faster)
o Concentration gradient (steeper -> faster)
o Surface area (larger -> more)
o Temperature (more energy -> faster)
o Size of molecules (small molecules diffuse faster)

Question 10

Discuss the importance of active transport

Answer 10

an energy-consuming process by which
substances are transported against a
concentration gradient, e.g. ion uptake by root
hairs and uptake of glucose by epithelial cells
of villi

Question 11

Define enzymes

Answer 11

proteins that function as biological catalysts

Question 12

Define catalyst

Answer 12

a substance that speeds up a chemical reaction and is not changed by the reaction

Question 13

Explain enzyme action in terms of the ‘lock

and key’ model

Answer 13

This means the subtrate molecule with a shape that fits into the active site. Each enzyme will only act on 1 substance because it is one “lock” so there’s only 1 “key” used to open it

Question 14

Explain the effect of changes in temperature and pH on enzyme activity

Answer 14

Low temperature -> no kinetic energy -> no chance of subtrate and active site colliding
High temperature/extreme pH -> active site (lock) is changed -> enzyme is denatured -> subtrate (key) does not work
Optimum temperature and pH is best for the enzymes to work in

Question 15

List the chemical elements that make up:
• carbohydrates
• fats
• proteins

Answer 15

Carbs: carbon, hydrogen, oxygen
Fats: carbon, hydrogen, oxygen
Proteins: carbon, hydrogen, oxygen, nitrogen and sometimes phosphorus or sulfur.

Question 16

Describe the synthesis of large molecules from

smaller basic units

Answer 16

• simple sugars to starch and glycogen
• amino acids to proteins
• fatty acids and glycerol to fats and oils

Question 17

Describe tests for:
• starch 
• reducing sugars (carbs)
• protein 
• fats

Answer 17

Starch (Iodine solution):
- Positive: Blue black
- Negative: Yellow brown
Carbs (Benedict's solution):
- Positive: red
- Negative: blue
Protein (Biuret):
- Positive: Purple
- Negative: Blue
Fat (Ethanol):
- Positive: cloudy
- Negative: clear

Question 18

List the principal sources of, and describe the
importance of:
• carbohydrates
• fats
• proteins
• vitamins (C and D only)
• mineral ions (calcium and iron only)
• fibre (roughage)
• water

Answer 18

Carbs:
- It is used as an energy resource, essential in respiration to release energy.
- It is used in creating the cellulose, the substance forming cell walls of plant cells.
- Sources: honey,milk,bread
Fats:
- Release high amounts of energy
- Make cell membranes
- Store them under the skin to insulate heat.
- Forming a layer of fats around organs to protect them from damage
- Storing energy (better than glycogen)
- Sources: butter,oil
Proteins:
- Making and new body cells
- Growth and repair
- Making enzymes (they are proteins in nature)
- Build up hormones
- Making antibodies
- Sources: meat
Vitamins:
- Vitamin C is essential for the formation of Collagen, a protein that functions as cementing layer between cells, Vitamin C also increases immunity.
- Vitamin D plays a big role in absorbing Calcium from the small intestine and depositing it in bones. So it is responsible for having healthy bones.
- Sources: C- citrus fruits, D- milk, fish oil
Fibre:
- Helps the passage of food through the gut
- Absorbs poisonous wastes from bacteria in the gut
- Lowers the concentration of cholesterol -> reduce risk of heart disease
- Sources: vegetables
Water:
- For chemical reactions to take place in solution
- As chemicals passed out as urine, sweat -> water is needed

Question 19

Describe the deficiency symptoms for:
• vitamins (C and D only)
• mineral ions (calcium and iron only)

Answer 19

Vitamins C and D
- Scurvy is the deficiency disease of vitamin C. Its symptoms include bleeding gums.
- Rickets is the deficiency disease of both Vitamin D and Calcium. Bones are made of calcium which Vitamin D helps in depositing in the bones, if any of both is lacking in the diet, rickets is developed.
Mineral ions:
- Tiredness, lack of energy (anaemia) - lack of iron
- Weak, brittle bones and teeth, cramps - lack of calcium

Question 20

Define photosynthesis. State the word and balanced equation for the production of simple sugars and oxygen

Answer 20

the fundamental process by which plants manufacture
carbohydrates from raw materials using energy from light
Word: carbon dioxide + water (sunlight and chlorophyll) -> glucose + oxygen
Balanced: 6CO2 + 6H20 (sunlight and chlorophyll) -> C6H12O6 +O2

Question 21

Describe the uses, benefits and health hazards associated with food additives,including colourings

Answer 21

Advantages
•	Prevents rotting
•	Improve color
•	Improve flavor
•	Keeps texture
•	Increases lifespan
•	Prevents poisoning
Disadvantages
•	Allergic reactions
•	Cause hyperactivity
•	Damages liver/kidney
•	Carcinogenic
•	Makes bad food look good

Question 22

Investigate the necessity for chlorophyll, light
and carbon dioxide for photosynthesis, using
appropriate controls

Answer 22

We can test to see that light, chlorophyll and co2 are needed by not giving plants each of these and testing leaves for starch.

Question 23

Define the term limiting factor

Answer 23

something present in the environment in such short

supply that it restricts life processes

Question 24

Explain the concept of limiting factors in photosynthesis

Answer 24

light intensity, temperature and carbon dioxide concentration are limiting factors.

Question 25

What does chlorophyll do?

Answer 25

traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent
storage

Question 26

Explain the use of carbon dioxide enrichment,
optimum light and optimum temperatures in
glasshouse systems

Answer 26

Temperature:
- sunlight heats up the inside of the glasshouse and glass stops a lot of heat from escaping.
- electric heaters are used in cold weather
- ventilator flaps are opened to cool the glasshouse on hot days
Light: the glass allows sunlight to enter. Artificial lighting can be used when light intensity is too low. Blinds keep out strong light

Question 27

State the parts of the leaves and their functions

Answer 27

Order (from top of leaves to bottom)

• Upper epidermis: single layer of cells with no chloroplasts -> light goes straight through
• Cuticle: waterproof layer to prevent too much water being lost
• Palisade mesophyll: contains palisade cells which contain lots of chloroplasts for photosynthesis
• Vein: contains xylem vessels that bring water and salts to the leaf and phloem tubes that take dissolved food away
• Spongy mesophyll: contains palisade cells, however, the cells are more rounded giving more air spaces between the -> allow gases to pass into and out of the leaf
• Lower epidermis contains lots of stomata to allow gases diffuse in and out