2.1 Structure and function of eukaryotic cells Flashcards
What is the structure of a nucleus?
- contains hereditary material
- usually spherical
- between 10-20μm in diameter
What is the function of the nucleus? (x4)
- controls the cells activities
- acts as the control centre through production of mRNA and tRNA for protein synthesis
- contains genetic information in the form of DNA and chromosomes
- makes ribosomal RNA and ribosomes
What is the structure of the nuclear envelope?
- double membrane that surrounds the nucleus
- outer membrane is connected with endoplasmic reticulum and often has ribosomes on its surface
What is the function of the nuclear envelope? (x2)
- controls what enters and exists the nucleus
- contains the reactions happening inside the nucleus
What is the structure of the nuclear pores?
- 3000 pores in each nucleus
- 40-100nm in diameter
What is the function of the nuclear pores?
- allows large molecules to pass through
What is the structure of the nucleolus?
- small spherical region in nucleoplasm
What is the function of the nucleolus? (x2)
- makes ribosomal RNA
- assembles ribosomes
What is the structure of a chromosome?
- consists of protein bound, linear DNA
What is the structure of the mitochondria?
- usually rod shaped
- 1-10μm in length
- surrounded by double membrane folded inner membrane forms cristae
- contain 70S ribosomes
What is the function of the mitochondria?
- double membrane that controls what enters and leaves the mitochondrion
- produces ATP from respiration
What is the structure of cristae?
- extensions of the inner membrane
- large surface area for respiration
(mitochondria)
What is the structure of matrix?
- contains proteins, lipids, ribosomes, and DNA
What is the function of matrix?
- controls production of the mitochondrion’s own proteins
(mitochondria)
What is the structure of chloroplasts?
- usually disc-shaped
- 2-10μm in length
- double membrane (chloroplast envelope) that controls what enters and leaves the chloroplast
How are the chloroplasts adapted to their function?
Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis.
What is the structure of grana?
- stacks of up to 100 thylakoids
- thylakoids contain chlorophyll pigments
(chloroplast)
What is the structure of stroma?
- fluid-filled matrix
- contains starch grains
(chloroplast)
What is the function of chloroplasts?
- site of photosynthesis
- harvests sunlight
What is the structure of the endoplasmic reticulum?
- system of sheet-like membranes in the cytoplasm
- it is continuous with the outer nuclear membrane
What is the structure of the rough endoplasmic reticulum (RER)? (x2)
- ribosomes on the surface
- provides a large surface area for protein synthesis
What is the structure of the smooth endoplasmic reticulum (SER)?
- more tubular and no ribosomes
What is the function of RER?
- provide a pathway for transport of materials throughout the cell
- protein synthesis
What is the function of SER?
- synthesises, stores and transports lipids and carbohydrates
What is the structure of the Golgi apparatus?
- looks similar to SER, but more compact
- it consists of a stack of membranes that make up flattened sacs, or cisternae, with small rounded hollow structures called vesicles
What is the function of the Golgi apparatus?
- receives proteins from the ER
- modifies them e.g. adding sugars
- packages them into vesicles to be transported around the cell or to outside the cell
What is the structure of lysosomes?
- produced by the Golgi body
- vesicles that contain enzymes that break things down
What is the function of lysosomes? (x4)
- they can hydrolyse material ingested by phagocytic cells
- release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell
- digest worn out organelles so that the useful chemicals they are made of can be reused
- completely break down cells after they have died (autolysis)
- digests contents of phagosome
- exocytosis of digestive enzymes
What is the structure of ribosomes?
- not surrounded by a membrane
- very small organelles in the cytoplasm and bound to rough ER
- consists of 2 subunits - 80s and 70s
Where are 80s ribosomes found?
- in eukaryotic cells
- (25nm in diameter)
Where are 70s ribosomes found?
- in prokaryotic cells, mitochondria and chloroplasts
- slightly smaller than 80s
What is the function of a ribosome?
- site of protein synthesis which acts as an assembly line to use mRNA to assemble proteins
What is the structure of a cell wall?
- made up of a number of polysaccharides such as cellulose
- have a thin layer called the middle lamella
What is the function of the cell wall?
- provide mechanical strength-stop individual cells from bursting and to provide structure to the plant
- movement of water - allows water to pass along it
What is the structure of a vacuole?
- fluid filled sack
- single membrane (tonoplast)
- contains mineral salts, sugars, amino acids, pigments and other molecules
What is the function of a vacuole?
- provide support to the plant
- can act as a temporary food store
- pigments may colour petals
What are the two types of ER?
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
What is a eukaryotic cell?
- distinct nucleus
- membrane-bound organelles
What are vesicles?
Small structure within a cell, consisting of fluid enclosed by a lipid bilayer
What is a turgid plant cell?
Cell swells a bit but cell wall prevents lysis
Describe the structure and function of the cell surface membrane.
• Fluid mosaic phospholipid bilayer with extrinsic and intrinsic proteins embedded
• isolates cytoplasm from extracellular environment
• selectively permeable to regulate transport of substances
• involved in cell signalling/cell recognition
Explain the role of cholesterol, glycoproteins and glycolipids in the cell surface membrane.
cholesterol = steroid molecule connects phospholipids and reduces fluidity
glycoproteins = cell signalling, cell recognition and binding cells together
glycolipids = cell signalling and cell recognition
What are some common cell adaptation?
• folded membrane or microvilli increase surface area e.g. for diffusion
• many mitochondria = large amounts of ATP for active transport
• walls one cell thick to reduce distance of diffusion pathway
