The Ultrastructure of eukaryotic
cells: Membrane-Bound
organelles
Do now: List all of the organelles you can remember
Organelles within Eukaryotic cells
Within each cell there are tiny structures called
organelles. Each organelle has a specific function which
allows a cell to carry out its many functions more
efficiently due to the labour being divided amongst them.
Organelles in Eukaryotic cells
• Most of the organelles in Eukaryotic cells are membrane bound
• This means they are covered in a membrane which keeps the
organelle separate from the rest of the cell
Nucleus
• A nucleus surrounded by a
nuclear envelope and
containing DNA organised
and wound into linear
chromosomes
• The nucleolus – an area
inside the nucleus
containing RNA, where
chromosomes unwind. It is
also involved in making
ribosomes and RNA
Rough endoplasmic reticulum
• RER is the intracellular
transport system: the
cisternae form
channels for
transporting
substances from one
area of a cell to
another
• It provides a large
surface area for
ribosomes, which
assemble amino acids
into proteins
Smooth Endoplasmic reticulum
• This is a system of membranes containing
cisternae that are continuous with the
nuclear membrane
• SER contains enzymes that catalyse reactions
involved with lipid metabolism e.g. synthesis
of cholesterol, lipids/phospholipids and
steroid hormones
• No ribosomes on its surface unlike the RER
Golgi apparatus
• This consists of a stack of membrane-bound flattened
sacs.
• Proteins are modified by adding sugar molecules to
make glycoproteins, adding lipids to make lipoproteins,
being folded into their 3D shapes
• Proteins are packaged into vesicles and then either,
stored in the cell, incorporated into the plasma
membrane or exported from the cell
Mitochondria
• Surrounded by two membranes. The inner
membrane is highly folded into cristae
• Site of ATP production during aerobic
respiration
• Self-replicating
• Abundant in cells where metabolic activity
takes place
Chloroplasts
•
•
•
•
Large organelles 4-10 micrometers long
Site of photosynthesis
Surrounded by a double membrane
First stage (when light is trapped by chlorophyll
and used to make ATP) occurs in the grana. Water
is also split to supply hydrogen ions
• Second stage (when hydrogen reduces carbon
dioxide to make carbohydrates) occurs in
the stroma​
• Chloroplasts are abundant in the leaf cells
(palisade mesophyll layer)
Vacuole
• Surrounded by a membrane called
the tonoplast and contains fluid
• Only plant cells have a large permanent
vacuole
• It is filled with water and solutes and
maintains cell stability because when
full it pushes the cell wall, making the cell
turgid
• This helps to support the plant
Lysosomes
• These are small bags, formed by Golgi
• They contain powerful hydrolytic
(digestive) enzymes
• They are abundant in phagocytic cells
• Lysosomes can engulf old cell organelles
and foreign matter, digest them and return
the digested components to the cell for
reuse
Cilia and undulipodia
• They are protrusions from the cell and are surrounded
by the cell surface membrane
• Each contains microtubules
• They are formed from centrioles
• The epithelial cells lining your airways have many
hundreds of cilia that waft mucus
Questions: Write down 1-7
1. Name one substance that passes out of pores in the nuclear envelope to
the cell cytoplasm RNA and Proteins
2. Name one substance that passes into the nucleus via the pores in the
nuclear envelope ATP or Nucleic acids or Steroid Hormones
3. Describe the role of the nucleolus Ribosome synthesis and RNA synthesis
4. State two functions of the nucleus Regulate cells activities and carries the genes
5. Name one type of human cell that does not contain a nucleus Red blood cell
6. Suggest why hydrolytic enzymes within cells need to be inside a vesicle
Very acidic and can digest the cell from the inside out
7. If you carried out a physical training program, how and why would you
expect the number of mitochondria in your muscle cells to change?
Increase as more mitochondria are required for aerobic respiration
Organelles:
- Vacuole
- Cell wall
- Centrosome
- Chloroplast
- Peroxisome
- Cytoskeleton
- Cytoplasm
- Cell membrane
- Smooth
Endoplasmic
reticulum
- Rough
Endoplasmic
reticulum
- Lysosomes
- Nucleus
- Nucleolus
- Secretory Vesicle
- Golgi Apparatus
- Mitochondria