2.1 - Cell Structure

Question 1

Describe the stages in the production of extracellular proteins

Answer 1

• nucleus contains gene which codes for protein
• transcription produces mRNA
• ribosomes / RER are the site of translation
• protein transported to Golgi
• Golgi apparatus processes and packages proteins into vesicles
• vesicles move towards cell surface membrane
• vesicles fuse with cell surface membrane
• protein released out of cell by exocytosis

Question 2

Stages of exocytosis

Answer 2

• vesicles move towards cell surface membrane
• along microtubules
• vesicles fuse with cell surface membrane
• protein released out of cell by exocytosis
• the movement of vesicles on microtubules and fusion of vesicles with membrane requires ATP

Question 3

Stages of endocytosis

Answer 3

• a molecule binds to a receptor
• this causes cell surface membrane to invaginate
• this requires ATP
• the membrane fuses with itself
• to form a vesicle
• vesicle moves through cytoplasm to its destination organelle

Question 4

Roles of the cytoskeleton

Answer 4

• cell support and stability to maintain shape
• movement of cilia
• movement of flagellum to move cell
• changing shape of cell e.g./ endocytosis / exocytosis
• to move organelles moved inside the cell
• to anchor organelles
• movement of chromosomes and mRNA

Question 5

Microtubules

Answer 5

Size
hollow cylinders of tubular 25nm

Roles

• maintain cell shape and anchor organelles
• make up 9+2 flagellum (and cilia) structure in eukaryotes
• move vesicles using microtubule motors(require ATP) - spindle fibres move chromosomes

Question 6

Intermediate filaments

Answer 6

Size
keratin cables 10nm

Roles
- maintain cell shape and anchor organelles

Question 7

Actin Microfilaments

Answer 7

Size
2 twisted actin strands 7nm

Roles

• maintain cell shape
• cause muscles contraction - involved in cytokinesis
• allow pseudopodia

Question 8

Organisation of cells in a multicelluar organism

Answer 8

• cells differentiate
• groups of similar specialised cells working together to perform a common functions form tissues
• groups of tissues working together form organs
• groups of organs working together form organ systems