eukaryotic cells Flashcards
cell surface membrane description
the membrane found on the surface of animal cells and just inside the cell wall of other cells
made mainly of lipids and protein
cell surface membrane function
regulates the movement of substances into and out of the cell
it also has receptor molecules on it, which allow it to respond to chemicals like hormones
nucleus description
a large organelle surrounded by a nuclear envelope which contains many pores
the nucleus contains chromosomes which are made from protein-bound linear DNA and one or more structures called a nucleolus
nucleus function
the nucleus controls the cell’s activities by controlling the transcription of DNA
DNA contains instructions to make proteins
The pores allow substances to move between the nucleus and the cytoplasm
The nucleolus makes ribosomes
Mitochondrion description
They’re usually oval-shaped
Have a double membrane - the inner one is folded to form structures called cristae
Inside is the matrix, which contains enzymes involved in respiration
Mitochondrion function
The site of aerobic respiration, where ATP is produced
Found in large numbers in cells that are very active in required a lot of energy
Chloroplast description
A small, flattened structure found in plant and algal cells
Surrounded by a double membrane, also has membranes inside called thylakoid membranes
These membranes are stacked up in some parts of the chloroplast to form grana
Grana are linked together by lamellae - thin, flat pieces of thylakoid membrane
Chloroplast function
The site where photosynthesis takes place
Some parts of photosynthesis happen in the grana, and other parts happen in the stroma (thick fluid found in chloroplasts)
Golgi apparatus description
A group of fluid-filled, membrane-bound flattened sacs
Vesicles are often seen in the edges of the sacs
Golgi apparatus function
It processes and packages new lipids and proteins
It also makes lysosomes
Golgi vesicle description
A small fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the golgi apparatus
Golgi vesicle function
stores lipids and proteins made by the golgi apparatus and transports them out of the cell via the cell-surface membrane
lysosome description
a round organelle surrounded by a membrane, with no clear internal structure
it’s a type of golgi vesicle
lysosome function
contains digestive enzymes called lysozymes
These are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell
Ribosome description
a very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum
It’s made up of proteins and RNA
It’s not surrounded by a membrane
Ribosome function
The site where proteins are made
Rough endoplasmic reticulum description
A system of membranes enclosing a fluid-like space
The surface is covered with ribosomes
Rough endoplasmic reticulum function
folds and processes proteins that have been made at the ribosomes
Smooth endoplasmic reticulum description
similar to rough endoplasmic reticulum but with no ribosomes
smooth endoplasmic reticulum function
synthesises and processes lipids
cell wall description
a rigid structure that surrounds cells in plants, algae and fungi
in plants and algae it’s made mainly of the carbohydrate cellulose
in fungi, it’s made of chitin
cell wall function
supports cells and prevents them from changing shape
cell vacuole description
a membrane-bound organelle found in the cytoplasm of plant cells
it contains cell sap - a weak solution of sugar and salts
the surrounding membrane is called the tonoplast
cell vacuole function
helps to maintain pressure inside the cell and keep the cell rigid
This stops plants wilting
Also involved in the isolation of unwanted chemicals inside the cell
organelles in specialised cells vary - why?
the organelles in the cell are the ones the cell needs to do it’s job - eg if the cell uses a lot of energy, it’ll needs lots of mitochondria - it if makes a lot of proteins, it’ll need a lot of ribosomes
epithelial cell example
in small intestine - specialised to absorb food efficiently
walls of the small intestine have a lot of finger-like projections called villi - these increase surface area for absorption
on the surface of the villi have folds in their cell-surface membranes called microvilli - further increase surface area
also have lots of mitochondria to provide energy for transport of digested food molecules into the cell
tissue
specialised cells that are grouped together, to work together to perform a particular function
different tissues work together to form organs
