Chapter 1: Cell Structure and Transport

Question 1

The Microscope

Answer 1

• Light microscopes magnify up to about x2000 and have a resolving power of about 200nm.
• Electron microscopes magnify up to about x2000000, and have a resolving power of about 0.2
• Magnification = size of image / size of real object

Question 2

Animal and Plant cells

Answer 2

• Ribosomes are where protein synthesis takes place in both animal and plant cells

• Plant cells also have
vacuoles, cell walls and chloroplasts

Question 3

Eukaryotic and Prokaryotic cells

Answer 3

• Eukaryotic cells have a cell membrane, cytoplasm, and genetic material enclosed inside a nucleus.
• Prokaryotic cells consist of cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not in a distinct nucleus, it forms a single DNA loop. Prokaryotic cells may also contain one or more extra small rings of DNA called plasmids.
• Bacteria are prokaryotic.

Question 4

Specialisation in animal cells

Answer 4

• As an organism develops, cells differentiate to form different types of cells
• As an animal cell differentiates to form a specialised cell it acquires different sub cellular structures to enable it to carry out a certain function
• Examples: nerve cells, muscle cells, sperm cells
• May be specialised for a function inside a tissue, organ, organ systems or whole organisms.

Question 5

Specialisation in plant cells

Answer 5

• May be specialised to carry out a particular function
• Examples: root hair, photosynthetic, xylem, and phloem cells.
• May be specialised for a function inside a tissue, organ, organ systems or whole organisms.

Question 6

Diffusion

Answer 6

• Diffusion is the spreading out of particles of any substance, in a solution or gas, resulting in a net movement from an area of high concentration to a low concentration, down a concentration gradient.
• The rate of diffusion is affected by the difference in concentrations, temperature, and the variable surface area.
• Dissolved substances like glucose, co2, oxygen, urea move in and out cells through diffusion

Question 7

Osmosis

Answer 7

• It is the movement of water from a dilute to a concentrated solute solution through a partially permeable membrane.
• Differences is concentration in and out the wall cause water to move in or out the cell
• Animal cells can be damaged if the concentration outside the cell changes rapidly

Question 8

Active Transport

Answer 8

• Moves substances from low to high gradient (against concentration gradient)
• Uses energy from respiration to transport substances
• Allows plant root hairs to absorb all the mineral ions required for healthy growth
• Allows sugar molecules used for respiration to be absorbed from the low concentrations in the gut into the high concentration blood

Question 9

Exchanging Materials

Answer 9

• Single celled organisms have a relatively large surface area to volume ratio so all necessary exchanges with the environment take place over this surface
• In multicellular organisms, many organisms are specialised with effective exchange surfaces
• Exchange surfaces usually have a large surface area and thin walls, which give short diffusion distances.
• In animals, exchange surfaces will have an efficient blood supply or, for gaseous exchanges be ventilated.