Lecture 4- structure and function of cell organelles

Question 1

Nucleus

Answer 1

-Relatively large
-Contains cell genome
-Chromatin condenses to form chromosomes during division
-Double membrane ‘nuclear envelope’ contains pores
-Nucleolus- visible in interphase, involved in production of ribosomal RNA to form ribosomes
-Shape maintained by protein skeleton ‘nuclear matrix’

Question 2

Endoplasmic reticulum

Answer 2

System of membranous tubules an sacs
Highly folded with lumen region

Question 3

Rough ER

Answer 3

Intracellular highway for molecules movement and modification
Studded with ribosomes
Processes proteins to be exported from cell
Proteins with ‘signal sequence’ directed into ER lumen

Question 4

Smooth ER

Answer 4

Specialised for metabolism and storage
Has embedded transmembrane enzymes involved in production/processing of lipids and carbohydrates
Synthesis of steroids, toxin breakdown in liver cells
Main site of new membrane synthesis

Question 5

Golgi apparatus structure

Answer 5

System of membrane sacs (cisternae) with associated vesicles
Cis- nearest centre of cell
Trans- nearest plasma membrane

Question 6

Golgi apparatus function

Answer 6

Works with ER
Modifies proteins
Materials packaged into membrane enclosed vesicles, distributed within cell or exocytosed

Question 7

Lysosomes and endosomes

Answer 7

Loosely related single-membrane bound compartments in cell
Vesicles contain digestive enzymes produced from ER/ Golgi fuse and form lysosome
Lysosome is a membrane bound vesicle of hydrolytic digestive enzymes
common in animal, fungi and protists, rare in plants
specialised membrane with transporters to export digestion products

Question 8

Mitochondria

Answer 8

Powerhouse of cell
Small (1-4 x 0.2-1 micrometers)
two membranes
Inner membrane has cristae to increase SA
Quantity differ depending on cell type
Inner membrane imbedded with metabolic proteins
Source of ATP
Have own genome

Question 9

Plastids

Answer 9

Only found in plants and algae
Most common is chloroplast
5-8 x 2-4 micrometers
Double membrane at border
Distinct genome- circular DNA molecules

Question 10

Chloroplast

Answer 10

Example of a plastid
Contain chlorophyll
Protein photoreceptors on thylakoid membrane are site of photosynthesis and ATP production

Question 11

Embosymbiont theory

Answer 11

Observation that mitochondria and chloroplasts ahem one genomes and bacterial-like DNA
Theory is that mitochondria and chloroplasts were originally independent prokaryotes engulfed by ancestral eukaryotic cell

Question 12

Vacuole

Answer 12

Fluid-filled membrane-bound sacs
Take up 90% of plant cells
Storage area containing water and chemicals eg, sugars & ions
Bound by tonoplast membrane with protein pumps
Provide high turgor pressure (pushes against rigid cell wall to Gove strength)

Question 13

Ribosomes

Answer 13

Sites of protein synthesis
Small, dense, numerous
Composed of numerous proteins and RNA molecules

Question 14

Centrioles

Answer 14

Found in animal cells
Either side of nucleus during nuclear division
create spindle apparatus

Question 15

Cytoskeleton