3.1, 3.2, 3.3, 3.4, 3.5 Cells and Cellular Structure Flashcards
3.1 Know that all living organisms are made of cells, sharing some common features. 3.2 Know the ultrastructure of eukaryotic cells, including nucleus, nucleolus, ribosomes, rough and smooth endoplasmic reticulum, mitochondria, centrioles, lysosomes, and Golgi apparatus. 3.3 Understand the role of the rough endoplasmic reticulum (rER) and the Golgi apparatus in protein transport within cells, including their role in the formation of extracellular enzymes. 3.4 Know the ultrastructure of prokaryot
All living organisms are made of cells, sharing some common
features. True or false?
true
What are organelles?
subcellular structures that have one or more specific jobs to perform in the cell
What is cell ultrastructure?
the internal structure of a cell and the internal structures of organelles only visible using an electron microscope
What are the two types of cells?
- prokaryotic cells
- eukaryotic cells
What are eukaryotic cells?
cells that contain their DNA inside a nucleus and have discrete membrane bound organelles
List the organelles of a eukaryotic cell (9):
- nucleus
- mitochondria
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- golgi apparatus
- ribosomes
- centrioles
- lysosomes
- cell surface membrane
Describe the structure of the nucleus:
- looks like a fried egg
- a large organelle surrounded by a nuclear envelope (DOUBLE MEMBRANE)
- the nuclear envelope contains many nuclear pores (gaps in the nuclear envelope)
- has a nucleolus is present (‘yolk’)
- contains chromatin made from DNA and histone proteins (little squiggles in the ‘egg white’)
What is the function of the nucleus and its internal structures?
- the nucleus controls the the cell’s activity by controlling the transcription of DNA
- the nuclear pores allow substances (e.g. mRNA) to move between the nucleus and the cytoplasm
- the nucleolus makes ribosomes
Describe the structure and function of a lysosome:
- a round organelle sorrounded by a membrane, with no clear internal structure
- it contains digestive enzymes
- the membrane keeps these digestive enzymes separate from the cytoplasm
- the digestive enzymes are used to break down foreign material, ingested material in vesicles, old organelles, and old cells
Describe the structure and function of a ribosome:
- it is a very small organelle that either floats free in the cytoplasm or is attached to the RER
- it is made of proteins and RNA
- it is not surrounded by a membrane
- its has a small subunit and a large subunit
- it is the site of protein synthesis
Describe the structure and function of the rough endoplasmic reticulum:
- a system of interconnected, membrane bound, flattened sacs called cisternae filled with fluid
- the surface is covered by ribosomes (rough)
- it folds and processes proteins that have been made at the ribosomes (so they assume their 3D shape)
Describe the structure and function of the smooth endoplasmic reticulum:
- it has a similar structure to RER (- a system of interconnected, membrane bound, flattened sacs filled with fluid)
- but no ribosomes are attached (smooth)
- it synthesises and processes lipids and steroids (e.g. reproductive hormones)
Describe the structure and function of the golgi apparatus:
- stacks of membrane-bound flattened sacs called cisternae (like a wifi signal)
- formed by the fusion of vesicles from the ER
- vesicles are seen at the edge of the sacs
- it modifies proteins and packages them in vesicles for transport
- it also makes lysosomes
Describe the structure and function of a mitochondria:
- oval shaped
- has a double membrane, with the inner membrane folded into finger-like projections called cristae
- inside is the matrix, which contains enzymes involved in respiration
- it is the site of aerobic respiration where stalked particles on the cristae catalyses the synthesis of ATP
- fat is digested here if it is used as an energy source
- contains a loop of DNA (mtDNA)
Describe the structure and function of a centriole:
- every animal cell has a pair of centrioles
- they are small, hollow cylinders made of nine protein microtubules arranged in a helix
- they are not surrounded by a plasma membrane
- involved in spindle fibre formation in animal cells, and the separation of chromosomes during cell division
What are prokaryotic cells?
cells which do not contain DNA within a nucleus, and which do not have other membrane bound organelles
List the organelles of a prokaryotic cells and specify which are present in all prokaryotic cells (9):
- structures always present:
- cell wall
- cell surface membrane
- ribosomes
- circular DNA
- mesosome
- structures not always present:
- plasmids
- capsule
- pilli
- flagellum
Describe the cell wall of a prokaryotic cell and its function:
- made of murein (peptidoglycan) - a type of polysaccharide and polypeptide combined
- supports the cell and prevents it from changing shape
Describe the cell surface membrane of a prokaryotic cell and its function:
- same as eukaryotic cells - made of lipids and proteins
- controls the movement of substances into and out of the cell
Describe a ribosome of a prokaryotic cell and its function:
- the same ribosomes as eukaryotes - the site of protein synthesis
- except they are smaller than eukaryotes
- eukaryotes = 80s
- prokaryotes = 70s
Describe the circular DNA of a prokaryotic cell and its function:
- the DNA floats free in the cytoplasm as one long coiled up strand
- it is not attached to histone proteins
Describe the mesosome of a prokaryotic cell and its function:
- inward folds in the cell surface membrane
- likely to be the site of respiration
- however some believe they are artefacts produced when cells are being prepared for viewing with an EM
Describe a plasmid of a prokaryotic cell and its function:
- small loops of DNA
- contain genes for antibiotic resistance
- can be passed between prokaryotes
- some cells have none, some have several
Describe the capsule of a prokaryotic cell and its function:
- a layer made of secreted slime
- protects the cell from attack and prevents dehydration
