2.1.1 - Cells Flashcards
Nucleus
- Comprised of nuclear envelope with nuclear pores, nucleolus and DNA molecules
- It contains coded genetic information in the form of DNA molecules
- Controls the activities of the cell
- DNA associates with proteins called histones to form a complex called chromatin. Chromatin coils and condenses to form structures known as chromosomes
Nucleolus
- Area within the nucleus
- Responsible for producing ribosomes
- It is composed of proteins and RNA
- RNA is used to form rRNA which is then combined with proteins to form ribosomes
Nuclear envelope
- Double membrane
- Protects DNA from damage
- Has nuclear pores
- The pores allow substances to move in and out of the nucleus
Mitochondria
- Site of aerobic respiration
- ATP produced
- Release energy
- Double membrane
- Inner membrane highly folded to form cristae
- Fluid interior is called matrix
- Membrane forming the cristae contains the enzymes used in aerobic respiration
- Contains small amount of DNA - can produce their own enzymes and reproduce themselves
Ribosome
- Floats freely in the cytoplasm or is attached to the RER
- Not surrounded by a membrane
- Site of protein synthesis
Lysosome
- Round organelle surrounded by a membrane
- Contains hydrolytic/digestive enzymes: Kept separate from cytoplasm by the membrane
- Responsible for breaking down waste material (cells/ pathogens)
- Programmed cell death or apoptosis
Vesicles
- A small fluid filled sac surrounded by a membrane
- Transports substances in and out of the cell, via the cell surface membrane and between organelles
Golgi apparatus
- Group of flat fluid filled sacs
- Modifies proteins (add carbohydrates/sugars)
- Repackages them into vesicles
- Makes lysosomes
Endoplasmic reticulum
- A network of membranes enclosing flattened sacs called cisternae
- RER: Ribosomes bound to surface
- RER folds and processes proteins, packages them into vesicles
- SER : Synthesises and processes lipids/ carbohydrates/steroid hormones
Centrioles
- Component of cytoskeleton
- Small hollow cylinders containing microtubules
- Two associated centrioles form the centrosome, which is involved in the assembly and organisation of the spindle fibres
- In organisms with flagella and cilia, centrioles play a part in positioning them
Cilia
- Small hairlike structure found on the membrane
- Moves substances across the cell surface
- Stationary cilia/ mobile cilia
- Two central microtubules surrounded by nine pairs of microtubules
- Pairs of parallel microtubules slide over each other causing the cilia to move in a beating motion
Flagella
- Tail-like structure
- Enables cell to move
- In some cells they are used as a sensory organelle detecting changes in the cell’s environment
Cell wall
- Made of cellulose
- Freely permeable
- Substances can pass in and out
- Gives it shape
- Contents of the cell press against cell wall making of rigid
- Defence mechanism against invading pathogens
Vacuole
- Membrane lined sac
- Contains cell sap
- Large permanent vacuole
- Important in maintenance of turgor
- Membrane of vacuole(tonoplast)it is selectively permeable
- Animal cells (small and transient)
Chloroplast
- Responsible for photosynthesis
- Found in green parts of plants
- Double membrane
- Fluid enclosed in chloroplast(stroma)
- Internal network of membranes which form flattened sacs called thylakoids
- Several thylakoids stacked together(granum)
- Grana are joined together by membranes called lamellae
- Grana contain chlorophyll pigments
- Starch present as starch grains
- Contain DNA and proteins
Cytoskeleton
- Present throughout cytoplasm
- Network of fibres
- Microfilaments: Contractile fibres made from protein actin. Cell movement and cell contraction during cytokinesis
- Microtubules : Globular tubulin polymerises to form tubes that form a scaffold-like structure that determines the shape of the cell
- Intermediate fibres - These fibres give mechanical strength to cells and help maintain integrity.
Function of cytoskeleton
- Maintain shape
- Movement of vesicles
- Enabling cell movement
- Provides stability
- Movement of RNA or chromosomes
- Hold organelles in place
- Provide mechanical strength
Eukaryotic cells
Eukaryotic cells are cells with a nucleus and other membrane-bound organelles
Prokaryotic cells
Cells with no membrane-bound nucleus
P vs E(Size)
- 1 to 10 micrometer
- 10 to 100 micrometer
P vs E(Nucleus)
- Not present
- Present
P vs E (DNA)
- Circular, one main molecule of DNA, additional DNA can be found in plasmids, genes on the chromosomes are often grouped into operons
- Linear, DNA associated with histone proteins, additional DNA found in mitochondria and chloroplast
P vs E (Organelles)
- Non membrane-bound
- Both membrane-bound and non membrane-bound
P vs E (Cell wall)
- Peptidoglycan
- Chitin in fungi, Cellulose in plants, Not present in animals
P vs E(Ribosomes)
- Smaller 70S
- Larger 80S
P vs E (Cytoskeleton)
- Present
- Present (more complex)
P vs E (reproduction)
- Binary fission
- Asexual or Sexual
P vs E (cell type)
- Unicellular
- Unicellular and multicellular
Protein production
- Nucleus produces mRNA
- Proteins are synthesised by the RER
- They are packaged into vesicles
- The vesicles travel along the cytoskeleton to the Golgi apparatus
- The Golgi apparatus modifies the proteins(carbohydrates added)
- They are then packaged into secretory vesicles
- Secretory vesicles transport the protein to the plasma membrane
- The vesicles fuse with plasma membrane and the contents are released by exocytosis.
Organelles of plant cells that are not in animal cells
- Cellulose cell wall
- Chloroplast
- Large permanent vacuole or tonoplast
Organelle present in animal cells but not in plant cells
- Centrioles
- Lysosomes
Why can’t light microscope observe small organelles
- They are too small
- Resolution of light microscope not high enough
- Wavelength of light too long
What feature of a eukaryotic cell would a prokaryotic cell not have
- Nucleus
- Mitochondria
- Endoplasmic reticulum
- Golgi body
Feature of prokaryotic cell not found in eukaryotic cell
- Plasmid
- Nucleoid/ Free DNA
- 70S ribosomes
P vs E ( Diameter of cell)
- 0.5 to 5 micrometer
- 20- 40 micrometer
Two processes that rely on cytoskeleton for movement
- Chromosomes (Cell division)
- RNA ( Protein synthesis)
Why does the nuclear envelope have pores
- To allow movement of substances in or out of the nucleus
- RNA moves to the ribosomes
