cell structure and organisation

Question 1

definition of a cell

Answer 1

• a unit of life
• consists of a mass of living matter called protoplasm

Question 2

cell membrane

Answer 2

• surrounds the cytoplasm of the cell
• made up of lipids and proteins
• partially permeable membrane : allows only some substances to pass through it
• controls the movement of substances in and out of the cell

Question 3

cell wall

Answer 3

• plant cell only
• made of cellulose
• protects the cell from injury
• gives the plant cell a fixed shape
• fully permeable

Question 4

cytoplasm

Answer 4

• jelly-like substance that fills the inside of the cell
• where most cell activities occur

Question 5

nucleus

Answer 5

• surrounded by a membrane : nuclear membrane
• controls cell activities such as cell growth and repair of worn-out parts
• essential for cell division
  chromosomes :
• made up of a molecule called DNA
• hereditary information is stored in DNA
• 46 chromosomes in each human body cell
• control cell activity
  nuclear membrane :
• separates the contents of the nucleus from the rest of the cytoplasm

Question 6

vacuole

Answer 6

• plant cells have a large, central vacuole which contains a liquid called cell sap
• cell sap contains dissolved substances such as : sugars, mineral salts and amino acids
• animal cells have many small vacuoles that contain water and food substances

Question 7

mitochondria

Answer 7

• small oval shaped organelles
• break down glucose in the presence of oxygen to release energy for cell activites (aerobic respiration)

Question 8

ribsomes

Answer 8

• small round structures
• either attached to organelles within the cell or lie freely in the cytoplasm
• needed to synthesise proteins in the cell

Question 9

chloroplasts

Answer 9

• oval structure
• contain a green pigment called chlorophyll, which is essential for photosynthesis

Question 10

definition of differiantiation

Answer 10

process by which a cell becomes specialised for a specific function

Question 11

red blood cell

Answer 11

• contains haemoglobin which binds to oxygen and transports around the body
• has a circular, biconcave shape which increases its surface area-to-volume ratio so that oxygen can diffuse in and out at a higher rate
• no nucleus : enabling the cell to store more haemoglobin for the transport of oxygen
• is flexible and can squeeze through capillaries easily

Question 12

muscle cell

Answer 12

• is elongated and cylindrical in shape, contains many nuclei and mitochondria
• has mitochondria to provide energy for the contraction of the muscle cell

Question 13

root hair cell

Answer 13

• has a long and narrow root hair to increase surface area-to-volume ratio to absorb water and mineral salts at a higher rate