Cell Architecture

Question 1

What are the general features of a eukaryotic cell?

Answer 1

Eukaryotic cells are compartmentalised which allows speciation
The isolated compartments create functionalised subgroups

Question 2

Describe the nucleus, nuclear lamina and nucleolus

Answer 2

The nucleus protects the genome from enzymes
Contains continuous memory with endoplasmic reticulum
The nuclear pore governs movement of molecules
Structurally be held together by lamina
Lamina is a meshwork of interconnected proteins which gives shape and stability and interacts with proteins on the inner nuclear membrane and interact with chromatin
it also acts as an anchoring site for chromosomes and the cytoplasmic cytoskeleton
lamins depolymerise during mitosis
Nucleolus is the largest structure in the nucleus
it is not membrane-bound
it is primarily the site of ribosome synthesis and assembly
could have more than one and can be different sizes
is known to capture and immobilise proteins - a process known as nucleolar detention

Question 3

Describe the rough and smooth endoplasmic reticulum

Answer 3

The endoplasmic reticulum is 10% of cell volume and is composed of tubules called cisternae and is constantly regenerating for the vesicular trafficking
Smooth endoplasmic reticulum is responsible for the synthesis of lipids/steroid hormones/carbohydrate metabolism/access calcium storage
The detoxification of harmful metabolic by products
It is prominent in cells of the liver that process harmful chemicals and in cells of the endocrine system such as those in the adrenals that produce steroid hormones and in excitable cells such as neurons and muscle cells that use ca2+ signalling
The rough endoplasmic reticulum is a net like labyrinth of tubes and sacs
it’s connected to the nuclear envelope
there are ribosomes attached to ensure proteins are folded correctly
Where disulphide bond formation occurs
has a more neutral pH
occurs more in plasma cells which produce large amounts of antibodies and endocrine cells

Question 4

Describe the Golgi apparatus

Answer 4

Golgi apparatus is a membrane-bound organelle which is not contiguous
It is smooth tubular ordered stacks of flattened cisternae which have polarity
It has a cis face which is closer to the endoplasmic reticulum and receives lipids/proteins
And it has a trans-face which is closer to the plasma membrane
It has a more acidic pH
It is thought to be the post office as it sorts and packages proteins into membrane-bound vesicles to be sent to appropriate destinations
It is where post-translational modification occurs
vesicles are tagged to direct the destination, tags can be phosphate groups/proteins
They are found in secretory cells or cells which produce large amounts of a substance that your body needs

Question 5

Describe lysosomes

Answer 5

Lysosomes contain over 60 digestive enzymes, they are enclosed by a lipid bilayer, they have a low pH (five)
They are thought to be the waste disposal centre - where autophagy (digesting damaged cell and diseased tissue), involved in phagocytosis, occurs
There are many in the cell usually spherical but vary in size
Only found in animal cells - human cells contain around 300

Question 6

Describe endosomes

Answer 6

• sorting organelles that originate from Golgi apparatus
• Enclosed in lipid bilayer
• formed by endocytosis
  3 types:
• early: sorting proteins
• recycling: bring back to PM
• Late: Target protein for degradation

Question 7

Describe peroxisomes

Answer 7

• membrane bound organelles, roughly spherical, enclosed in lipid bilayer
• contain oxidative enzymes like catalase and urate oxidase
• take organic substances and oxidise them into hydrogen peroxide
• Catalase decompose H2O2 into water or use it to oxidise another compound - including phenols, formic acid formaldehyde and alcohol
• involved in breakdown of long fatty acid chains through beta oxidation which produces ATP energy
  Found in liver cells - lots of peroxisomes to oxidise alcohol

Question 8

Describe the difference between lysosomes and peroxisomes

Answer 8

Lysosomes break down biological polymers like proteins and polysaccharides
Peroxisomes oxidise organic compounds, breaking down metabolic hydrogen peroxide’s
L consists of degradative enzymes
P consists of oxidative enzymes
L responsible for digestion in the cell
P responsible for protection of the cell against metabolic hydrogen peroxide
L found in animals only
P found in all eukaryotes
L derived from golgi or ER
P derived from ER and capable of replication
L larger than P
L involved in endocytosis, autophagy and phagocytosis
P involved in biosynthesis of lipids and photorespiration
L do not generate energy whereas P generate ATP energy

Question 9

Describe plastids

Answer 9

- double membrane bound organelles
E.g mitochondria, chloroplasts, chloroplast like organelles (apicoplast)
- generate ATP
- contain their own genome
- some use in storage or synthesis roles