Lesson 1: Review: Ultrastructure of Eukaryotic Cells

Question 1

Primary Cell Structure

Answer 1

Primary cell structure refers to the structures that can be seen using a light microscope.
Eukaryotic cell organelles that are visible using light microscopy:

Nucleus

Cytoplasm

Cell Membrane

Cell Wall

Chloroplast

Question 2

Cell Ultrastructure

Answer 2

Refers to structures that can be seen using an electron microscope.
Eukaryotic cell organelles that are visible using electron microscopy:

Mitochondria

Ribosomes

Endoplasmic Reticulum

Golgi

Nucleolus

Chromatin

Question 3

NUCLEUS

Answer 3

Functions

Main site of DNA in eukaryotic cells

Preservation, replication and expression of genetic information

It makes RNA for protein synthesis

It copies DNA for cell division

Question 4

MITOCHONDRION

Answer 4

Functions

The inner membrane contains the enzyme necessary for the synthesis of
Adenosine Triphosphate (ATP)

The mitochondria are closely associated with the pathways of respiration

These metabolic pathways are divided up and supported by the membranes

Question 5

CHLOROPLAST

Answer 5

Function: Photosynthesis

The metabolic pathways are closely associated with the membranes as in the
case of the mitochondrion

Question 6

Organelles
and Evolution

Answer 6

Both chloroplasts and mitochondria are double membrane bound
They involved in energy reactions
They contain extranuclear DNA and characteristic small ribosomes of their own

This has led biologists to believe that there may be some similarity in their origins in the cells of eukaryotes.

The endosymbiotic theory

Question 7

LYSOSOME

Answer 7

Not discovered by electron microscopy but by centrifugation and enzyme analysis

Structure

Simple, spherical, single membrane bound

Lysosomes contain a large number of CATABOLIC enzymes. Catabolic enzymes
digest materials by hydrolysis

Function

Digestion of compounds taken in by the cell by endocytosis

Recycling of material within the cell

Question 8

GOLGI APPARATUS

Answer 8

Functions

Processing and packaging

Synthesising lysosomes to contain the potentially dangerous catabolic enzymes

Producing secretory vesicles e.g. mucus

Making more plasma membrane

Question 9

ER

Answer 9

Functions

Not easy to study the ER is that it is difficult to extract intact

ER starts the biosynthetic pathways form many protein and lipid molecules in
the cell

These continue in the Golgi apparatus

Rough ER has ribosomes attached to it as opposed to Smooth ER

The proteins are made on rough ER will eventually be secreted outside the cell

Question 10

RIBOSOME 1

Answer 10

NOT membrane bound

Found both in pro- and
eukarotes

The subunits are
synthesised separately
in the nucleolus of the
nucleus of eukaryotes

Question 11

RIBOSOME 2

Answer 11

Distribution in the cytoplasm

single free-floating

attached to rough ER

linked together as a POLYRIBOSOME or POLYSOME

Function

Protein synthesis