Cell Ultrastructure Flashcards
What is the description and function of a nucleus?
• Present in all eukaryotic cells.
• Controls the cell’s activities.
• Surrounded by a nuclear envelope (double membrane) which has many pores.
• Nuclear pores allow substances (like RNA) to move between the nucleus and cytoplasm.
• The nucleus contains chromatin.
• The nucleus contains a nucleolus, the site of ribosome production.
What is the description and function of ribosomes?
• Found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells.
• Each ribosome is a complex of ribosomal RNA (rRNA) and proteins.
• 80S ribosomes are found in eukaryotic cells.
• 70S ribosomes are found in prokaryotic cells.
• Site of protein synthesis.
What is the description and function of a plasma membrane?
• All cells are surrounded by a plasma membrane which controls the exchange of materials into and out of the cell.
• It is partially permeable.
• It is formed from a phospholipid bilayer.
• It also has receptor molecules on it, which allow it to respond to chemicals like hormones.
What is the description and function of a lysosome?
• Found in animal cells.
• Round organelle surrounded by a membrane.
• Contains hydrolytic enzymes.
• Break down waste materials such as worn-out organelles.
• Used extensively by cells of the immune system and in apoptosis.
What is the description and function of a cell wall?
• Found in plants, bacteria, and fungi cells.
• They are formed outside of the cell membrane and offer structural support to the cell.
• In plants it is made of cellulose.
• In bacteria it is made of peptidoglycan.
• In fungi it is made of chitin.
What is the description and function of the rough endoplasmic reticulum?
• Found in plant and animal cells.
• Formed from continuous folds of membrane continuous with the nuclear envelope.
• Surface covered in ribosomes.
• Processes proteins made by the ribosomes.
What is the description and function of the smooth endoplasmic reticulum?
• Found in plant and animal cells.
• Doesn’t have ribosomes on the surface.
• Involved in the production, processing and storage of lipids, carbohydrates, and steroids.
What is the description and function of a vesicle?
• Found in plant and animal cells.
• Membrane-bound, fluid-filled sac in the cytoplasm.
• It is for transport and storage.
What is the description and function of a golgi apparatus?
• Found in plant and animal cells.
• Flattened sacs of membrane.
• Modifies proteins and lipids before packaging them into Golgi vesicles.
• Also makes lysosomes.
What is the description and function of a mitochondrion?
• Found in all eukaryotic cells.
• Usually oval-shaped.
• Surrounded by a double membrane with the inner membrane folded to form cristae.
• The matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP.
• Small circular pieces of DNA and ribosomes are also found in the matrix (needed for replication).
What is the description and function of a chloroplast?
• Found in plant cells.
• Surrounded by a double membrane.
• Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana.
• Grana are joined together by lamellae (thin and flat thylakoid membranes).
• Chloroplasts are the site of photosynthesis.
• The light-dependent stage takes place in the thylakoids.
• The light-independent stage takes place in the stroma.
• Chloroplasts also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis.
What is the description and function of a centriole?
• Found in animal cells.
• Hollow cylinders made of microtubules.
• Two centrioles at right angles to each other form a centrosome, which organises the spindle fibres during cell division.
What is the description and function of a cilia?
• Found on the surface membrane of some animal cells.
• Hair-like projections made from microtubules.
• Allows the movement of substances over the cell surface.
What is the description and function of a flagella?
• Found in specialised cells.
• Made of microtubules.
• Microtubules contract to make the flagellum move.
What is the description and function of a microvilli?
• Found in specialised animal cells.
• Cell membrane projections.
• Used to increase the surface area of the cell surface membrane to increase the rate of exchange of substances.
