cell structure

Question 1

nucleus (3 fxn)

Answer 1

1. contain hereditary material (DNA)
2. control cell activity by regulating protein synthesis
3. contains enzymes for DNA replication, transcription and RNA processing

Question 2

nucleus (structure)

Answer 2

largest organelle, spherical with nuclear envelope that has nuclear pores

Question 3

nucleolus

Answer 3

1. synthesise rRNA (component of ribosomes)
2. site of assembly of rRNA and proteins into large and small ribosomal subunits

Question 4

chromatin

Answer 4

thin elongated DNA threads coiled around histone protein, exits as euchromatin (active) and heterochromatin (inactive)

Question 5

chromatin (fxn)

Answer 5

contains genes which undergo transcription to form mRNA which undergo translation at ribosomes to form polypeptides

Question 6

S: rER

Answer 6

network of flattened sacs called cisternae, with ribosomes on outer surface and continuous with outer mem of nuclear envelope

Question 7

F: rER (3)

Answer 7

1. transport proteins to Golgi via transport vesicles
2. allow proteins to fold into conformation
3. glycosylated proteins into glycoproteins

Question 8

S: sER

Answer 8

network of tubular sacs called cisternae, lacking ribosomes

Question 9

F: sER

Answer 9

1. synthesise lipids and carbs
2. detoxify drugs and poisons
3. store Ca2+ ions

Question 10

S: Golgi

Answer 10

cis face (new cisternae form from fusion of vesicles from ER) and trans face (golgi vesicles bud off)

Question 11

F: Golgi (5)

Answer 11

1. glycosylate proteins into glycoproteins AND glycolipids by adding short sugar chains
2. modify existing glycoproteins and glycolipids by cleaving sugar chains
3. sort and package proteins into vesicles, targeting proteins to diff parts of cell or for secretion
4. form lysosomes
5. produce polysacch like pectin

Question 12

Lysosome (4)

Answer 12

membranous sac containing hydrolytic enzymes that
1. digest material taken in by cell during endocytosis
2. release enzymes from cells by exocytosis for extracellular digestion
3. autophagy - digest unwanted organelles
4. autolysis - self-destruct a cell after its death

Question 13

S: Mitochondrion

Answer 13

spherical or rod-shaped surrounded by double membrane: outer is smooth while inner is highly convoluted with infoldings (cristae)

has a semi-fluid matrix containing circular DNA, 70s ribosomes, phosphate granules and enzymes for aerobic resp

Question 14

F: Mitochondrion

Answer 14

1. site of stages of aerobic respiration to generate energy as ATP
   (oxidative phosphorylation across mitochondrial membrane and link reaction + Krebs cycle in mitochondrial matrix)

Question 15

S: Chloroplast

Answer 15

lens-shaped with double membrane, internal membrane system with thylakoids (containing chlorophyll) and stroma fluid (similar to semi-fluid matrix)

Question 16

F: Chloroplast

Answer 16

convert solar energy to chemical energy via photosynthesis : light-dependent reactions in thylakoid and light-independent reactions in stroma

Question 17

S: ribosome

Answer 17

small and large subunit, each made up of protein and rRNA assembled in nucleolus
freely floats in cytosol or bound to ER

Question 18

F: ribosome

Answer 18

site of protein synthesis

Question 19

S: centrioles

Answer 19

pair of hollow cylinders made up of 9 triplets of microtubules
two rod-like cylinders at right angles to each other found in centrosome

Question 20

F: centrioles

Answer 20

organise spindle fibres during nuclear division and determine polarity of cell