WEEK 3 - CELLS & ORGANELLES

Question 1

What are cells?

Answer 1

Cells are the smallest living units, >200 types in human body

Question 2

What is cytoplasm?

Answer 2

• Cytoskeleton (scaffold) and organelles (machinery)
• Inclusions (stored products e.g., glycogen)
• In a clear gelatinous cytosol

Question 3

What is nucleus?

Answer 3

• Control centre
• DNA (46 chromosomes)

Question 4

What is nucleolus?

Answer 4

• Assembles ribosomes

Question 5

What is nuclear envelope?

Answer 5

• Two membranes around nucleus.
• Perforated by pores (stuff in or out)

Question 6

What is rough endoplasmic reticulum?

Answer 6

• Covered with ribosomes
• Continuous with nuclear envelope
• Produces phospholipids
• Produces and packages proteins

Question 6

What is endoplasmic reticulum?

Answer 6

Network of membranous channels and sacs within the cytoplasm

Question 7

What is smooth endoplasmic reticulum?

Answer 7

• Lacks ribosomes
• Synthesizes steroids from cholesterol (hormones), glycogen, stores calcium
• Detoxifies alcohol and other drugs (liver)

Question 8

What are ribosomes?

Answer 8

• Produce proteins
• Firstly, the DNA strands of a gene separate in the nucleus
• This DNA transcribed into messenger Ribonucleic Acid (mRNA) by RNA Polymerase
• Ribosome ‘Reads’ this mRNA and translates into a language of amino acids.

Question 9

What is Golgi complex?

Answer 9

• Membranous
• Modifies these new proteins and packages them into vesicles (membranous sacs)
• Carbohydrate synthesis

Question 10

What are lysosomes?

Answer 10

• Membranous
• Package of hydrolytic enzymes (>40 types)
• Break down (e.g., glycogen) and destroy stuff

Question 11

What is mitochondria?

Answer 11

• Double membrane
• Structure = Inner membrane folds - cristae
• Surface area of three soccer fields (1000’s per cell)
• Synthesize Adenosine Triphosphate (ATP = energy)
• Requires oxygen (O2) and fuel (e.g., glucose)

Question 12

What are centrosome?

Answer 12

• Structure = Two short cylinders of microtubules (centrioles)
• Organizes microtubules in MITOSIS

Question 13

What are cytoskeleton?

Answer 13

• Structure, support, strength, transport system
• Proteins (pasta) organised as:
• Microfilaments (fine)
• Intermediate filaments (thick)
• Microtubules (thickest)

Question 14

What is plasma membrane?

Answer 14

• Border of cell and some organelles
• Bilayer of phospholipids and proteins in a constantly changing fluid mosaic
• Separates intracellular from extracellular fluid
• Provides intracellular ‘order’
• Dynamic role in cellular activity

Question 15

Composition??

Answer 15

• Lipids: Phospholipids, cholesterol, glycolipids
• Proteins - Determines membrane function e.g., receptors, enzymes, channels, adhesion

Question 16

What is microvilli?

Answer 16

• Extensions of plasma membrane
• surface area x 40
• Absorptive and sensory

Question 17

What is cilia?

Answer 17

• Non-motile cilia (~one per cell) = Hair-like, longer than microvilli. Microtubules enclosed by membrane
• Motile cilia (50 to 200 per cell) = Antennae - monitoring nearby conditions e.g., inner ear sensing motion
• Beat in waves, sweep substances across surfaces e.g., respiratory tract (mucosa)