Key concepts in biology

Question 1

SB1b Plant and animals cells

Describe how;
A) Cells for digestion
B) Ciliated epithelial cells
are adapted to their function

Answer 1

A) The cells that line the small intestine absorb small food molecules produced by disgestion.
- Adapted by having membrane with many small tiny folds called microvilli.
- These adaptations increase the surface area of the cell. ( More area for molecules to be absorbed = faster absorbtion happens )

B) Cells in the lining of the oviduct transport egg cells towards the uterus. The oviduct cells are adapted by having hair-like cilia.
- These are like short sperm cell tails and move from side to side to sweep substance along.
- Cilia are covered in cell membrane and contain strands of a substance that can cause them to contract and have wavy movement.

Question 2

SB1f Testing foods

Describe the test for;
A) Reducing sugars
B) Starch

Answer 2

A) Benedicts Test:
- Mix the food solution with an equal volume of Benedicts solution and place it in a hot water bath for a few minutes.
- If reducing sugars are present, a reduction reaction occurs, which changes the colour of the solution depending on concentration of reducing sugars.
- Blue ( Low ) -> Green -> Yellow -> Orange -> Brick Red ( High )

B) Iodine Solution:
- Iodine solution changes from yellow-orange to blue-black when in contact with starch.

Question 3

SB1f Testing foods

Describe the test for;
A) Protein
B) Fats & Oils

Answer 3

A) Biuret Test:
- Potassium hydroxide is mixed with a solution of the food.
- 2 drops of copper sulfate solution are then added. If the pale blue solution turns purple, protein is present

B) Ethanol Emulsion Test:
- The food is mixed with ethanol and shaken. Some of that mixture is then poured into water & shaken again.
- Fats & oils dissolved in the ethanol float to the surface, forming a cloudy emulsion, when the mixture is left to stand.