Ultrastructure of eukaryotic cells Flashcards
what is the structure of the cytoplasm
- it contains a network of threads and microtubules that help the cell maintain its shape and form.
- it is a thick solution that fills each cell composed of water, salts and proteins.
- includes all of the material in and out of cell. all organelles are located in the cytoplasm. it is highly organised
what is the function of the cytoplasm
- transport & structure
- maintains the cells shape
- protects and stores macromolecules
- site of metabolic processes
- contains all organelles
what is the structure of the nucleus
- its the largest organelle
- surrounded by a double membrane called the nuclear envelope
- the nuclear envelope has pores containing proteins that control the exit of substances from the nucleus
what is the function of the nucleus
- control centre of the cel
- stores the organisms genome
- transmits genetic information
- provides instructions for protein synthesis
- the nuclear envelope separates contents of nucleus from the rest of the cell
- in some regions, the outer and inner nuclear membranes fuse together. some dissolved substances pass through
what is the structure of the nucleolus
- doesnt have a membrane around it
- contains RNA
- dark region of chromatin, involved in making chromosomes
- the chromatin is the genetic material consisting of DNA wound around histone proteins. when the cell is not dividing, chromatin is spread out or extended. when the cell is about to divide, chromatin condenses and coils tightly into chromosomes.
what is the function of the nucleolus
- where ribosomes are made
- chromosomes contain the organisms genes
- during cell division, chromatin becomes condensed into discrete observable chromosomes
- senses cellular stress. alteration of transfer RNA
what is the structure of the mitochondria
- may be spherical, rod shaped or branched about 2-5μm long.
- surrounded by two membranes with a fluid filled space between them.
what is the function of the mitochondria
- site of ATP production during aerobic respiration
- self replicating so more can be made if the cell’s energy need increases
- abundant in cells where much metabolic activity takes place
- inner membrane is studded with stalked particles which are the site of ATP synthesis
what is the structure of the chloroplast
- large organelles about 4-10μm
- in plant cells and some protoctists
- surrounded by double membrane or envelope
- inner membrane is continuous with membrane sacs (thylakoids) which contain chlorophyll. each stack of thylakoids is a granum
what is the function of a chloroplast
- site of photosynthesis.
- 1st stage occurs in the grana - light energy is trapped by chlorophyll and used to make ATP. water is split to supply hydrogen ions.
- 2nd stage occurs in stroma. when hydrogen reduces CO2 using energy from ATP to make carbohydrates
what is the structure of a ribosome
- small spherical organelles about 20nm in diameter.
- made of ribosomal RNA
- made in nucleolus as two separate subunits which pass through the nuclear envelope into the cell cytoplasm and then combine
- some remain free in cytoplasm and some attach to the endoplasmic reticulum
what is the function of a ribosome
ribosomes bound to the rough endoplasmic reticulum are mainly for synthesising proteins that will be exported outside the cell.
ribosomes that are free in the cytoplasm either singly or in clusters are the site of assembly of proteins that will be used inside the cell
what is the structure of the cell membrane
thin flexible layer around the outside of all cells made of phospholipids and proteins
what is the function of the cell membrane
seperates content of the cell from the outside environment and controls the entry and exit of materials
what is the structure of the cell wall
on the outside of the plasma membrane in plants. made from bundles of cellulose fibres. fungi also have cell walls made of chitin.
what is the function of the cell wall
only in plants
prevent plant cells from bursting when turgid.
- provides strength and support
- maintains cell shape
- contribute to strength and support of the whole plant
- permeable, to allow solutions to pass through
what is the structure of the smooth endoplasmic reticulum
system of membranes containing fluid filled cavities that are continuous with the nuclear membrane. no ribosomes on its surface
what is the function of the smooth endoplasmic reticulum
contains enzymes that catalyse reactions involved with lipid metabolism such as
- synthesis of cholesterol
- synthesis of lipids/phospholipids needed by the cell
- synthesis of steroid hormones
involved with absorption, synthesis and transport of lipids
what is the structure of the rough endoplasmic reticulum
similiar to SER but studded with numerous ribosomes giving its rough appearance
what is the function of the rough endoplasmic reticulum
The ribosomes synthesise proteins, which are processed in the RER (e.g. by enzymatically modifying the polypeptide chain, or adding carbohydrates), before being exported from the cell via the Golgi Body.
what is the structure of the Golgi body or apparatus
consists of a stack of membrane bound flattened sacs. secretory vesicles bring materials to and from the Golgi Apparatus
what is the function of the Golgi Apparatus
proteins are modified
- sugar molecules added to glycoproteins
- lipid molecules to lipoproteins
proteins are packaged into vesicles that are pinched of and stored in cell or move to plasma membrane for use or to be exported out of the cell
what is the structure of the vacuole
vacuole is surrounded by a membrane called the tonoplast and contains fluid
what is the function of the vacuole
only in plants
filled with water and solutes and maintains cell stability. when it is full, it pushes against the cell wall making the cell turgid. if all plant cells are turgid, this helps support the plant
