2.1 - Cell Structure

Question 1

Define the terms eukaryotic and prokaryotic cell

Answer 1

Eukaryotic: DNA is contained in a nucleus, contains membrane-bound specialised organelles
Prokaryotic: DNA is ‘free’ in cytoplasm, no organelles e.g. bacteria and archaea

Question 2

State the relationship between a system and specialised cells

Answer 2

Specialised cells → tissues that perform specific function → organs made of several tissue types → organ systems

Question 3

Describe the structure and function of cell-surface membrane

Answer 3

‘Fluid mosaic’ phospholipid bilayer with extrinsic & intrinsic proteins embedded

• isolates cytoplasm from extracellular environment
• selectively permeable to regulate transport of substances
• involved in cell singalling / cell recognition

Question 4

Explain the role of cholesterol, glycoproteins & glycolipids in the cell-surface membrane

Answer 4

Cholesterol: steroid molecule connects phospholipid & reduces fluidity
Glycoproteins: cell signalling, cell recognition (antigens) & binding cells together
Glycolupids: cell singalling & cell recognition

Question 5

Describe the structure of the nucleus

Answer 5

• Surrounded by nuclear envelope, a semi-permeable double membrane
• Nuclear pores allow substances to enter/exit
• Dense nucleolus made of RNA & proteins assembles ribosomes

Question 6

Describe the structure of a mitochondrion

Answer 6

• Surrounded by double membrane folded inner membrane folded inner membrane forms cristae : site of electron transport chain
• fluid matrix: contains mithochondrial DNA, respiratory enzymes, lipids proteins

Question 7

Describe the structure of a chloroplast

Answer 7

• Vesicular plastid with double membrane
• Thylakoids: flattened discs stack form grana ; contain photosystems with chlorophyll
• Intergranal lamellae : tubes attach thylakoids in adjacent grana
• Stroma: fluid-filled matrix

Question 8

State the function of mitochondria and chloroplasts

Answer 8

• MItochondria: site of aerobic respiration to produce ATP

- Chloroplasts: site of photosynthesis to convert solar energy to chemical energy