Organelles Flashcards
describe the cell-surface (plasma) membrane
- the membrane found on the surface of animal cells and just inside the cell wall of other cells
- it’s mainly made of lipids and protein
what’s the function of the cell-surface (plasma) membrane?
- regulates the movement of substances into and out of the cell
- also has receptor molecules on it which allow it to respond to chemicals like hormones
describe the nucleus
- a large organelle surrounded by a nuclear envelope (double membrane) which contains many pores (nuclear pores)
- contains chromosomes (made from protein-bound linear DNA) and one or more nucleoli
what’s the function of the nucleus?
- controls the cell’s activities (by controlling the transcription of DNA)
- DNA contains instructions to make proteins
what is the function of the nuclear pores?
- nuclear pores allow substances (like RNA) to move between the nucleus and the cytoplasm
what is the function of the nucleolus?
- makes ribosomes
describe the mitochondria
- usually oval-shaped
- have a double membrane
- the innemembrane is folded to form structures called cristae
- between these folds is a fluid-filled matrix which contains enzymes involved in respiration
what is the function of the mitochondria?
- the site of aerobie respiration
- aerobic respiration produces ATP (a common energy source in the cell)
which cells contain mitochondria in high quantities?
- cells that are very active and require a lot of energy
describe a chloroplast
- a small, flattened structure found in plant cells and algal cells
- they’re surrounded by a double-membrane and also have membranes inside called thylakoid membranes
- thylakoid membranes are stacked up in some parts of the organelle to form grana
- grana are linked together by lamellae (thin flat pieces of thylakoid membrane)
what is the function of a chloroplast?
- the site where photosynthesis takes place
- some stages of photosynthesis take place in the grana and other stages take place in the stroma
what is the function of a chloroplast?
- the site where photosynthesis takes place
- some stages of photosynthesis take place in the grana and other stages take place in the stroma
what is the stroma?
a thick fluid found in chloroplasts
describe the Golgi apparatus
- a group of fluid-filled, membrane-bound, flattened sacs
- vesicles are often seen at the edges of the sacs
what is the function of the Golgi apparatus?
- it processes and packages new lipids and proteins
- it also makes lysosomes
describe the Golgi vesicle
- a small, fluid-filled sac in the cytoplasm surrounded by a membrane and produced by the Golgi apparatus
what is the function of the Golgi vesicle?
- stores lipids and proteins made by the Golgi apparatus and transports them out of the cell (via the cell membrane)
describe a lysosome
- a type of Golgi vesicle
- a round organelle surrounded by a membrane with no clear internal structure
what is the function of a lysosome?
- it contains the digestive enzyme, lysozyme
- these enzymes are kept separate from the cytoplasm by the membrane
- they can be used to digest invading cells or to break down worn out components of the cell
describe a ribosome
- a very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum
- it’s made up of proteins and RNA
- not surrounded by a membrane
what is the function of a ribosome?
- the site where proteins are made
- performs protein synthesis
describe the rough endoplasmic reticulum
- a system of membranes enclosing a fluid-filled space
- the surface is covered with ribosomes
what is the function of the rough endoplasmic reticulum?
- folds and processes proteins that have been made by the ribosomes
describe the smooth endoplasmic reticulum
- similar to the RER but with no ribosomes
what is the function of the smooth endoplasmic reticulum?
- synthesises and processes lipids
describe the cell wall
- a rigid structure that surrounds cells in plants, algae and fungi
- in plants and algae it’s mainly made of cellulose
- in fungi, it’s made of chitin
what is the function of the cell wall?
- supports cell
- prevents cell from changing shape
describe the vacuole
- a membrane-bound organelle found in the cytoplasm
- contains cell sap (a weak solution of sugars and salts)
- the surrounding membrane is called the tonoplast
what is the function of the vacuole?
- helps to maintain pressure inside the cell and keep the cell rigid which prevents the plant from wilting
- also involved in the ionisation of unwanted chemicals inside the cell
