Cell structure Flashcards
Nucleus?
Contains DNA which codes for protein synthesis
Components: Nucleolus, nuclear envelope, nuclear pore, nucleoplasm, chromatin, inner and outer membrane
nuclear envelope?
separates DNA from cytoplasm, double membrane
Nuclear pore?
Allows for the transport of mRNA out of the nucleus
Nucleolus?
Site of the synthesis of rRNA and ribosomes (can be more that 1)
Ribosomes?
2 subjnits made of ribosomal RNA (rRNA): small subunit + large subunit. Made of protein and rRNA. Can be free or attached to rough endoplasmic reticulum
nuclearplasm?
granular, jelly-like material
chromosomes?
protein bound, linear DNA
Rough and Smooth endoplasmic reticulum
Both have folded membranes called cisternae
RER- the ribosomes on the cisternae make it rough, protein synthesis here
SER- no ribosomes, synthesis and store lipids and carbohydrates
golgi apparatus?
Cisternae: secretiry vesicles or lysosomes pinch off of cisternae carrying finished product
Molecules can be ‘labelled’ as to their destination (using receptors)
Functions of golgi apparatus?
Add carbohydrates to proteins: glycoprotein, transport, store and chemically modify lipids/ proteins, produce secretory enzymes, secrete carbohydrates, form lysosomes , packaging of newly produced proteins in Golgi vesicles
lysosome?
Sack of digestive enzymes
Function of lysosome?
Digest worn out organelles for reuse of materials, completely break down dead cells (phagocytes or body cells (autolysis)), release enzymes to outside of the cell to destroy material (exocytosis)
Mitochondria structure?
Double membrane: outer + folded inner which is called cristae separated by inter membrane space, inner solution=mitochondrial matrix, small circular DNA, 70S ribosomes
mitochondria function?
site of aerobic respiration, site of ATP production, the DNA loops code for enzymes required for respiration
80s/70s ribosomes?
80s = large ribosomes found in eukaryotic cells
70s= smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts
vacuole?
Fluid filled, surrounded by a single membrane called tonoplast
Makes cell turgid to provide support, temporary store of sugars and amino acids, can contain pigments to attract pollinators
thylakoids?
Folded membranes embedded with pigment in chloroplasts (chlorophyll), stacked× 2-100 = granum, between them= lamella
chloroplasts components?
Double membrane, thylakoid/ geranium, lamella, stroma, 70s ribosomes, starch granules, small DNA circles
chloroplasts stroma
Stroma= fluid, contains enzymes for reactions which are light independent
Why cristae?
Increase SA on which part of respiration process occurs
size and shape of mitochondria
cylinder shaped, 1-10 um in diameter: being a cylinder reduces diffusion distance between edge and centre, increases efficiency of aerobic respiration
vesicles as vacuoles (animal cells)
Contractile vacuole: small, membrane contained organelle. Maintains osmotic pressure
cell wall?
made of cellulose in plants and chitin in fungi
plasma membrane?
phospholipid bilayer+ molecules embedded within or attached to outside e.g carbohydrates, proteins, cholesterol
centrioles?
Two hollow cylinders perpendicular to each other, used in spindle formation in cell division (They release long, stiff fibres called micro tubules that split the cell appart during cell division). Not in plant cells.
chloroplasts structure?
2-10 um diameter, 1um thick
plant cell wall?
cellulose microfibrils in the polysaccharide matrix pectin, prevents osmotic lysis (cell bursting), strength and support, freely permeable to water
Plasmodesmata ?
narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells.
function of plasmodesmata
exchange large organic materials via cytoplasmic streaming, allow communication between adjacent cells
function of RER?
synthesis and transportation of proteins. The RER is continuous with the nuclear membrane.
function of SER?
Synthesis and storage of lipids and carbohydrates
what are all the membranes made of?
Phospholipids which are very dynamic: this is what allows membranes to be pinched off but also to merge with other membranes to release products
what does 1 gene code for?
Order of amino acids in 1 poly peptide
where does mRNA bind after leaving nucleus through nuclear pore?
To ribosomes on rough endoplasmic reticulum
what happens to polypeptide chain after being synthesised at RER?
Moves through cisternae of RER, away from nucleus, towards cell membrane
what is mRNA
copy of a segment of DNA
various sites/ stages of protein synthesis (simple)
mRNA in nucleus, mRNA on ribosomes on RER, polypeptide through RER, protein in transport vesicles, enter golgi body, become lysosomes or secretery vesicles, excretion of protein through exocytosis
Exocytosis?
mass transport of molecules out of the cell, process requires ATP, synthesised by mitochondria during aerobic respiration
how do lysosomes break down worn out organelles?
Membrane of lysosome murges with that of organelle, releasing digestive enzymes into organelle. Hydrolyses organelle
Autolysis?
Break down of dead cells: several lysosomes burst within a cell releasing digestive enzymes which hydrolise the cell
How do lysosomes partake in phagocytosis
Pathogens are engulfed by white blood cells and become trapped in a vacuole within the cell. Membrane of lysosome merges with that of vacuole, emptying digestive enzymes into vacuole to digest pathogen
describe the interrelationship between the nucleus, RER, golgi body and plasma membrane
synthesizing proteins
plasma membrane
controls entry and exit of molecules in and out of the cell. It is selectively permeable
Chromatin?
In nucleus, coils of DNA bound to protein. During cell division, condenses into chromosomes
Benefit of the structure of granum?
Large SA, efficient for trapping light energy
specific benefits of cells having organelles/ membranes?
Isolates harmful substances like digestive enzymes, concentrates enzymes in a smaller space for higher RoR, allows multiple reactions to occur simultaneously without interference (compartemenatlisation), allows the functions of mitochondria and chloroplasts, increases SA for enzyme attachment
