Structure And Function Of Eukaryotes And prokaryotes Flashcards
Describe the structure of the Nucleus.
- A large organelle surrounded by a nuclear envelope which contains many
pores. - Nucleus contains chromatin (seen as darkened patches on light micrograph) and a structure called a nucleolus.
Describe the function of the nucleus.
- Controls the cell’s activities.
- Controls the transcription of DNA.
- DNA contains the instructions needed to make proteins.
- Chromatin is made from DNA and proteins and condenses into visible chromosomes.
Describe the structure of Nuclear Envelope.
- A double membrane with fluid between that surrounds the nucleus.
- Nuclear pores are protein complexes with a channel through the centre.
Describe the function of the Nuclear Envelope.
- It separates the contents of the nucleus from the rest of the cell.
- Nuclear pores enable larger substances such as mRNA to leave the nucleus. Other substances such as some steroid hormones can enter the nucleus.
Describe the structure of the nucleolus.
- Most obvious structure in the nucleus.
- A dense spherical structure without a
membrane around it composed of proteins and RNA.
Describe the function of the nucleolus.
- RNA is used to produce ribosomal RNA, which is then combined with proteins to form ribosomes necessary for protein synthesis.
Describe the structure of the rough endoplasmic reticulum.
- A system of flattened membranes enclosing a fluid-filled cavities (sacs) called cisternae.
- Surface is coated with ribosomes.
Describe the function of the rough endoplasmic reticulum.
- Intracellular transport system: the cisternae form channels for transporting substances from one area of cell to another.
- Provides a large surface area for ribosomes to assemble amino acids into proteins for transport to Golgi apparatus.
Describe the structure of the smooth endoplasmic reticulum.
- A system of flattened membranes enclosing a fluid-filled cavities (sacs) called cisternae that are continuous with the nuclear membrane and RER.
- No ribosomes on the surface.
Describe the function of the smooth endoplasmic reticulum.
- Makes lipids, including the phospholipids for cell membranes.
- Contains enzymes that are known to detoxify lipid-soluble drugs and some harmful products of metabolism.
Describe the structure of a vesicle.
A small fluid-filled sac in the cytoplasm, surrounded by a single membrane.
Describe the function of a vesicle.
Transports substances in and out of the cell (via the plasma membrane) and between organelles.
Describe the structure of the golgi apparatus.
- A stack of membrane-bound flattened sacs (cisternae).
- Secretory vesicles bring materials to and from the Golgi apparatus.
Describe the function of the golgi apparatus.
- It modifies the proteins and lipids delivered to it from the RER and prepares them for secretion, then delivers them to the cell membrane via a vesicle.
- Responsible for the synthesis of lysosomes.
Describe the function of mitochondria.
- Site of aerobic respiration, where ATP is produced.
- They are self-replicating, so more can be made as needed for cells requiring large amounts of energy.
Describe the structure of mitochondria.
- They may be spherical, rod-shaped or branched and are 2 – 5 µm long.
- Surrounded by a double membrane with a fluid-filled space (matrix) between.
- Inner membrane highly folded into cristae.
Describe the structure of chloroplasts.
- Large organelles, 4 – 10 μm long.
- A double outer membrane and a complex arrangement of internal membranes that form thylakoids (which contain chlorophyll)
- Thylakoids are grouped into stacks called grana, joined by intergranal lamellae.
- Fluid-filled matrix is called the stroma.
Describe the function of chloroplasts.
- Site where photosynthesis takes place.
- Grana; Light energy is trapped by chlorophyll and used to make ATP & water is split into ions.
- Stroma: Where energy from ATP is used to make carbohydrates.
Describe the structure of a vacuole.
- Surrounded by a membrane called the tonoplast.
- Contains fluid.
Describe the function of a vacuole.
- Only plant cells have a permanent vacuole.
- Filled with water and solutes and maintains cell stability, as when full pushed against cell wall, making cell turgid.
Describe the structure of lysosomes.
- A round organelle surrounded by a single membrane, with no clear internal structure.
- These are small bags formed by the Golgi apparatus.
Describe the function of lysosomes.
- Contains powerful hydrolytic (digestive enzymes).
- Can engulf old cell organelles and foreign matter, digest them and recycle the material.
- Often abundant in phagocytic cells that can ingest or invade pathogens.
Describe the structure of plasma membrane.
- The membrane found on the surface of animal and just inside cell wall of plant cells and prokaryotic cells.
- Mainly made of lipids and protein.
Describe the function of plasma membrane.
Acts like a barrier to the cell, controlling what enters and leaves due to the differential permeability to different biological molecules and due to protein carriers that pump substances in and out.
Describe the structure of Cilia.
- Small, hair-like structures found on the surface membrane of some animal cells.
- Cross-section shows they have an outer membrane and a ring of 9 pairs of protein microtubules, with a single pair of microtubules in the middle.
Describe the function of Cilia.
- Microtubules allow cilia to move.
- Movement of cilia pushes substances along the cell surface.
- Occur in large numbers along cell surface.
- Nearly all cells in the body have one cilium that acts as an antenna and contains receptors to detect environment.
Describe the structure of Undulipodia (flagellum).
- Very similar to cilia (but longer).
- Small, hair-like structures that stick out from the cell surface and are surrounded by plasma membrane.
- Cross-section shows they have an outer membrane and a ring of 9 pairs of protein microtubules, with 2 microtubules in the middle.
Describe the function of Undulipodia (flagellum).
- Microtubules contract to make the flagellum move and propel cell forwards.
- Undulipodium is proper name as flagellum is also used for prokaryotic structure which is very different internally.
Describe the structure of Ribosomes.
- Small spherical organelles (20nm in diameter).
- Each ribosome consists of 2 sub-units.
- Made up of proteins and ribosomal RNA.
- Not surrounded by a membrane.
Describe the function of ribosomes.
- Site where proteins are made.
- Ribosomes attached to RER exterior make proteins to be exported outside cell.
- Free-floating ribosomes in cytoplasm
make proteins to be used inside the cell.
Describe the structure of Centrioles.
- Consists of 2 bundles of microtubules at right angles to each other.
- Microtubules made of tubulin protein subunits and arranged to form a cylinder.
Describe the function of centrioles.
- Involved with the separation of chromosomes during cell division.
- Chromosomes attach to middle of spindle and motor proteins walk along the tubulin threads, pulling chromosomes apart.
- Centrioles are involved in the formation of cilia and undulipodia.
Describe the structure of cellulose cell wall.
- A rigid structure that surrounds the plant cells.
- Made from bundles of cellulose fibres (carbohydrate).
Describe the function of cellulose cell wall.
- Strong and can prevent plant cells from bursting.
- Provides strength and support.
- Maintain cell shape
- Permeable due to plasmodesmata (pores within walls) and allow solutions through.
Key differences between prokaryotic cells and eukaryotic cells.
- the cells are much smaller
- no membrane bound organelles
- smaller ribosomes
- no nucleus
- cell wall made of murein
What might prokaryotic cells also contain?
- Plasmids
- A capsule around the cell
- Flagella
No membrane bound organelles in Prokaryotic cells.
- ribosomes
No membrane bound organelles in Eukaryotic cells
- Ribosomes
- Mitochondria
- Chloroplasts
- Endoplasmic Reticulum
- Golgi apparatus
- Nucleus
What are ribosomes in Prokaryotic cells?
70S - smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts.
What are ribosomes in Eukaryotic cells?
80S - large ribosome found in eukaryotic cells (25nm).
What is the nucleus in Prokaryotic cells?
- No nucleus - instead of a nucleus there is a single circular DNA molecule free in the cytoplasm which is not protein bound.
What is the nucleus in Eukaryotic cells?
- Nuclear envelope - double membrane.
- Nuclear pores.
- Nucleoplasm - granular, jelly-like material.
- Chromosomes - protein-bound, linear DNA.
- Nucleolus - smaller sphere inside which is the site of rRNA production
What is the cell wall in Prokaryotic Cells?
- Contains murein - a glycoprotein.
What is the cell wall in Eukaryotic cells?
Plants - made of microfibrils of the cellulose polymer.
Fungi - made of chitin, a nitrogen-containing polysaccharide.
What are plasmids in Prokaryotic cells?
Plasmids are small loops of DNA which only carry a few genes.
What is the capsule in prokaryotic cells?
- The capsule is a slimy layer made of protein.
- This prevents the bacteria from desiccating (drying out) and protects the bacteria against the host’s immune system.
What is the flagella in prokaryotic cells?
- The flagella rotates to enable the bacteria to move.
