Cell Ultrastructure Flashcards
What is the nucleus surrounded by?
The Nuclear Envelope-A double Membrane.
In what type of cell is a nucleus found?
All Eukaryotic (other than RBC)
How is the nucleus separated from the cytoplasm?
A Double Membrane
What is the size of the nucleus?
Relatively Large
What does the nuclear envelope contain?
Pores
What does the pores in the nuclear envelope allow?
Molecules (mRNA and ribosomes) to enter and leave the nucleus.
What 2 other features does the nucleus contain?
Chromatin and nucleolus
What is the nucleolus a site of?
Site of ribosome production.
What is chromatin?
Chromosomes made of sections of linear DNA tightly wound around proteins called histones.
What are the two types of Endoplasmic Reticulum?
Rough Endoplasmic Reticulum (RER)Smooth Endoplasmic Reticulum (ER)
Which Cells is RER found?
Plant and Animal Cells
What is the surface of RER covered in?
Ribosomes
What is RER formed of?
Continuous folas of membrane with the nuclear envelope.
What does the RER process?
Proteins made by the ribosomes.
Where is the ER found?
Plant and Animal Cells.
What on the surface does RER have that ER doesn’t have?
Ribosomes, function is distinct to the RER.
What processes is the RER involved in and for what molecules?
Production, Processing and storage of lipids, carbohydrates and steroids.
Where is the Golgi Apparatus found?
Plant and Animal Cells
What is the Golgi Apparatus like?
Flattened sacs of membrane, similar to the ER.
What is the role of the Golgi Apparatus?
Modifies proteins and lipids before packaging them into Golgi vesicles.
What does the Golgi Vesicles do?
Transport proteins and lipids to destination.
What happens to the proteins that go through the Golgi apparatus?
Usually exported, then put into lysosomes or delivered to membrane bound organelles.
Where are ribosomes found?
In all cells.
Which part of the cell are ribosomes found?
Found freely in the cytoplasm of all cells or as part of the RER.
What is each ribosome a complex of?
Ribosomal RNA (rRNA) and proteins.
What ribosomes are in Eukaryote’s?
80S ribosomes (60S and 40S subunits)
What ribosomes are in Prokaryote’s , Mitochondria and Chloroplasts?
70S ribosomes (50S and 30S subunits)
What are ribosomes the site of?
Translation (Protein Synthesis)
What are Lysosomes?
Specialist forms of vesicles which contain hydrolytic enzymes (break down biological molecules)
What do lysosomes break down?
Waste materials e.g. worn out organelles.
Which specific cells are Lysosomes used in?
Used extensively by cells of the immune system and in apoptosis.
In what type of cells are chloroplasts found?
In plant cells.
Are chloroplasts larger or smaller than Mitochondria?
Larger.
What are chloroplasts surrounded by?
A double membrane.
What is the membrane bound organelle which contains chlorophyll?
Thylakoids
What do the Thylakoids do?
Stack to form structures called grana.
What joins the grana together?
Lamellae.
Chloroplasts are the site of what
site of photosynthesis.
Where does the light-independent stage happen?
Stroma.
Where does the light-dependent stage happen?
Thylakoids.
What are all cells surrounded by?
A Plasma Membrane
What is the role of the Plasma Membrane?
Controls the exchange of materials between the internal cell environment and the external environment.
The Plasma Membrane is…
Partially Permeable.
The plasma cell membrane is formed from what?
A phospholipid bilayer of phospholipids around 10nm wide.
The structure looks static, but what is actually constantly moving?
The phospholipids and proteins forming the bilayer.
What are Centrioles?
Hollow fibres made of microtubules.
How is a Centrosomes formed?
Two centrioles at rights angles to each other.
What does a Centrosome do?
Organises the spindle fibres during cell division.
Where are the Centrioles not found?
In flowering plants and fungi.
What are cilia?
Hair like projections.
What are cilia made out of?
Microtubules.
What is the role of cilia?
Allows the movement of substances over cell surface.
Where is the flagella found?
Specialised Cells.
What is the structure of the flagella?
Made of long microtubes, similar to the cilia.
In what cells is the cell wall found?
In plant cells only.
Where is the cell wall and what is it’s role?
Formed outside of the cell membrane and offers structural support to cell.
How is this structural support given?
Given by the polysaccharide cellulose in plants and pepticloglycan in most bacterial cells.
What connects the cytoplasm of neighbouring plant cells to the cell wall?
Narrow threads (surrounded by cell membrane) called plasmodesmata.
What is the permeability of the cell wall to most substances?
Freely permeable.
The cell wall is freely permeable, unlike what other sub-cellular structure?
The Plasma Cell Membrane.
