2.4 Eukaryotic cell structure Flashcards
What are the 2 basic types of cells?
What is the difference between these cells?
Prokaryotes and Eukaryotes
PK:
- Simple undivided internal structure of only a cytoplasm
- Single celled
EK:
- Make up multicellular organisms (animals, plants, fungi)
- Complex internal structure (membrane-bound nucleus, membrane-bound organelles)
What does metabolism involve?
Synthesis (anabolism) and break down of molecules
*(reactions take place in cytoplasm)
Describe the properties and function of membranes
- Selectively permeable
- Separate cytoplasm from external environment
- Control movement of substances in/out of cell
- Quite fragile
Common features in all eukaryotic cells
*Refer to Figure 3 on p.g. 27
- Microtubule network
- Vesicles
- Nucleolous
- Nucleus
- Golgi apparatus
- Cytosol
- Ribosome
- Centriole
- Cell-surface membrane
- RER (rough endoplasmic reticulum)
- SER (smooth endoplasmic reticulum)
- Cytoskeleton
- Mitochondria
- Secretory vesicles
- What does the nucleus contain?
2. What is the function of this?
- Contains genetic info in the form of DNA
2. DNA directs synthesis of proteins - controls metabolism as many proteins are enzymes
What is the nucleus in?
A double membrane - nuclear envelope
What is the function of the nuclear envelope?
To protect the nucleus from damage in the cytoplasm
What does the nuclear envelope contain?
Nuclear pores
What is the function of nuclear pores?
Allow substances to move in and out of the nucleus
How does DNA leave the nucleus?
DNA too big to leave nucleus - transcribed into smaller RNA molecules; exported via nuclear pores
How is chromatin formed?
When DNA associates with histones (proteins)
How are chromosomes formed?
Chromatin coils + condenses
What is the nucleolus?
What is its function?
- Area within nucleus
- Made up of proteins and RNA
-Produces ribosomes
What is RNA in the nucleolus used for?
To produce ribosomal RNA (rRNA), which is then combined w/ proteins to form ribosomes
Describe the structure of the mitochondria
- Double membrane
- Inner membrane highly folded to form cristae
- Fluid interior = matrix
- Contain DNA - mitochondrial DNA (mtDNA)
What is the function of the mitochondria?
- Site of cellular respiration
- Stored energy made available by producing ATP
- Amount reflects how much energy the cell uses - active cells = lots
- Membrane forming cristae contains enzymes for aerobic respiration
- Can produce own enzymes + reproduce on its own
What are vesicles? What are they used for?
- Membranous sacs w/ storage + transport roles
- Consist of single membrane w/ fluid inside
- Used to transport materials inside cells
What are lysosomes?
Specialised vesicles that contain hydrolytic enzymes
What is the function of lysosomes
- Break down waste in cells
- Break down pathogens ingested by phagocytes
- Involved in programmed cell death (apoptosis)
What is the cytoskeleton? Where is it?
- Network of fibres required for shape and stability of
the cell - Present throughout cytoplasm of eukaryotes
What is the function of the cytoskeleton?
- Hold organelles in place
- Controls cell movement
What are the 3 components of the cytoskeleton?
Microfilaments
Microtubules
Intermediate fibres
What are microfilaments?
Contractile fibres made from actin
Responsible for cell movement and cell contraction during cytokinesis
*(Cytokinesis - when cytoplasm of 1 cell divides to form 2 daughter cells)
What are microtubules?
- Determine cell’s shape
- Help move organelles - Act as path for movement of organelles
What are spindle fibres?
- Made up of microtubules
- Role in chromosome separation during cell division
What is the function of intermediate fibres?
- Give mechanical strength to cells
- Help maintain cell’s integrity
What are centrioles?
- Components of cytoskeleton in eukaryotes (not flowering plants or fungi)
- Composed of microtubules
- 2 centrioles = centrosome
- Centrosome - involved in organisation of spindle fibres during cell division
What is the flagella and cilia? Compare them
Extensions protruding from some cells
-Flagella = longer but cilia = present in greater numbers
What are flagella used for?
- Enable cell motility
- Sensory organelles detecting chemical changes in cell’s env.
What 2 types can cilia be? Elaborate on them
Stationary:
- On surface of cells
- Roles in sensory organs e.g. nose
Mobile:
- Beat in rhythmic manner, creating current = causes adjacent fluid to move
E.G. In trachea; move mucus away from lungs to keep air passage clean
In fallopian tubes to move egg cells from ovary to uterus
*(Cilia are made up of microtubules)
What is the endoplasmic reticulum?
A network of membranes enclosing flattened sacs called cisternae
-Connected to outer membrane of nucleus
What is the role of the smooth endoplasmic reticulum (SER)?
Synthesis + storage of lipids + carbs
What is the role of the rough endoplasmic reticulum
(RER)?
- Has ribosomes bound to surface
- Synthesis + transport of proteins
Where can ribosomes be found?
- Free-floating in cytoplasm
- Attached to RER
What are ribosomes?
- No membrane
- Constructed of RNA made in nucleolus
- Site of protein synthesis
What is the golgi apparatus?
- Similar structure to SER
- Compact structure formed of cisternae
- No ribosomes
What is the function of the golgi apparatus?
- Modifying proteins + packing them into vesicles:
Secretory vesicles - if protein needs to leave cell
Lysosomes - if protein stays in cell
Describe the 5 stages of protein production
1) Proteins synthesised on ribosomes bound to RER
2) Pass into cisternae + packaged into transport vesicles
3) Vesicles containing the synthesised proteins move to Golgi apparatus via cytoskeleton
4) Vesicles fuse with Golgi apparatus - proteins enter.
Proteins are structurally modified before leaving Golgi
apparatus
5) Secretory vesicles carry protein, vesicle moves to + fuses with plasma membrane to release contents via exocytosis. Some vesicles form lysosomes - these contain enzymes for use in cells
