Cell theory and ultrastructure

Question 1

Features that eukaryotic and prokaryotic cells share

Answer 1

-Plasma cell membrane - controls what moves in and out of the cell
-Cytoplasm - jelly-like fluid that is the site of metabolic reactions
-Genetic material - DNA
-Ribosomes - The site of protein synthesis

Question 2

Nucleus structure and function

Answer 2

STRUCTURE
-Surrounded by a double membrane known as the nuclear envelope
-Has nuclear pores to allow substances to move in and out
-Contains chromatin (DNA and proteins)
FUNCTION
-Controls the functions of the cell
-Contains genetic information (DNA) which codes for proteins

Question 3

Nucleolus

Answer 3

-Nucleolus is a dark, dense region inside the nucleus
-Nucleolus synthesises ribosomal RNA (rRNA)
-Also assembles ribosome subunits

Question 4

Ribosomes

Answer 4

-Ribosomes are dense particles made up of DNA and proteins
-Ribosomes are found free in the cytoplasm of attached to the rough endoplasmic reticulum
-Ribosomes are the site of protein synthesis (mRNA translates polypeptides)

Question 5

Rough endoplasmic reticulum

Answer 5

-Rough endoplasmic is a network of membranes that are covered with ribosomes
-Rough endoplasmic reticulum synthesises and processes proteins
-Rough endoplasmic reticulum modifies and folds the protein before passing it to the Golgi body
-Provides a large surface area for protein synthesis

Question 6

Smooth endoplasmic reticulum

Answer 6

-Is also a network of membranes
-Smooth endoplasmic reticulum synthesises and transports lipids and steroids
-Involved in the detoxification of poison and drugs in the liver

Question 7

Golgi apparatus

Answer 7

-Golgi apparatus is a series of flattened membranous sacs
-Golgi appratus modifies and packages proteins and lipids
-Form secretory vesicles for exocytosis
-Produces lysosomes

Question 8

Centrioles

Answer 8

-Centrioles are small cylindrical structures made up of microtubules
-Occurs in pairs at the centrosome near the nucleus
-Centrioles organise the spindle fibres during cell division
-Involved in the formation of cillia and flagella

Question 9

Lysosomes

Answer 9

-Lysosomes are small vesicles that contain digestive enzymes such as lysozyme
-Single membrane
-Lysosomes break down worn out organells or pathogens
-Lysosomes can carry out autolysis (self- destruction) when the cell is damaged
-Lysosomes play an important part in phagocytic cells (e.g macrophages)

Question 10

Role of Golgi apparatus and Rough endoplasmic reticulum in protein transport in the cell

Answer 10

-Gene for a protein is transcribed in the nuclues, producing mRNA
-mRNA leaves the nucleus via the nuclear pores and attaches to the ribsomes (especially on the rough endoplasmic reticulum (RER)
-Ribosomes synthesise the proteins, and then the proteins enter the RER
-The RER modifies and folds the proteins, before packagin them up into transport vesicles, and sending them to the golgi apparatus
-The golgi apparatus further modifies the proteins e.g adding glycoproteins or sugars (glycosylation)
-The golgi protein then packages them up into secretory vesicles
-The secretory vesicles fuse to the plasma membrane and release their contents via exocytosis
-Now the protein is outside of the cell (extracellular enzyme)

Question 11

Special fact about RER

Answer 11

-RER folds peptides into their 3D shapes (secondary and tertiary structure)

Question 12

Ultrastructure of cell Wall

Answer 12

-Cell wall is made up of peptidoglycan
-Cell wall protects against osmotic lysis
-Cell wall maintains structural support and shape of the bacterial cell

Question 13

Capsule

Answer 13

-Capsule is a slime layer made up of polysaccharides that is only found on the surface of come bacteria
-Capsule protects against drying out
-Capsule protects against phagocytosis
-“stickiness” of capsule allows for cell surface adhesion

Question 14

-Flagellum

Answer 14

-Flagellum is a tail- like structure made of protein
-Enables motility

Question 15

Plasmids

Answer 15

-Plasmids are small loops of DNA that are independent from the main chromosome
-Plasmids often contain additional useful genes e.g a resistance to antibiotics

Question 16

Pilli

Answer 16

-Pilli are short, hair-like adhesions on the surface of the bacterial cell
There are two types of pilli:
Attachment pilli which are involved the bacterial cell’s adhesion to surfaces
and sex pilli, which are involved in conjugation (plasmids and DNA being exchanged between cells)

Question 17

Circular DNA

Answer 17

-Single, circular loop of DNA
-Contains the majority of the genetic material of the cell
-Free floating in the cytoplasm (no nucleus)
-Codes for essential proteins

Question 18

Differences between eukaryotic and prokaryotic cells

Answer 18

-Prokaryotic cells have no nucleus- DNA is free in the cytoplasm
-Eukaryotic cells have a nuclue

-Prokaryotic cells have no membrane bound organelles
-Eukaryotic cells have membrane bound organelles

-Prokaryotic cells has Circular DNA, with plasmids
-Eukaryotic cells have linear DNA

-Prokaryotic cells have 70s ribosomes
-Eukaryotic cells have 80S ribosomes

-Porkaryotic cells are smaller
-Eukaryotic cells are larger