cell structures and functions (pt 1) Flashcards
cell surface membrane thickness?
7nm
permeability of csm? and function
partially permeable and controls exchange between the cell and its environment
what is the microvilli
finger-like extensions of a cell (typical of certain animal cells, such as the epithelial cells) which increase the surface area of the cell for more efficient absorption or secretion
function of microvilli
(greatly) increase the surface area of the cell surface membrane
what are the benefits (examples) of the microvilli increasing the SA of CSM?
useful for
- reabsorption at the proximal convoluted tubules of the kidney
- absorption of digested food into the cells lining the gut
describe the nuclear envelope
surrounded by two membranes. the outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum
what are the pores in nuclear envelope
- called
- their function
- nuclear pores
2. allow and control exchange between the nucleus and the cytoplasm
example of substances leaving nuclear pores?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomes (for protein synthesis)
example of substances entering nuclear pores?
- proteins (to help make ribosomes)
- nucleotides
- ATP
- thyroid hormone T3
describe the content found in chromosomes
- chromosomes contain DNA
- DNA is organised into functional units called genes
- genes control the activities of the cell and inheritance
why do DNA molecules have to be folded?
- the are so long (human has around 2m of DNA).
- folded to a more compact shape to prevent the strands from becoming tangled.
how is DNA folded?
- this is achieved by combining with proteins (histones)
- the combination of DNA and proteins is known as chromatin
what are chromosomes made of?
- chromatin
- chromatin contain RNA
what is the endoplasmic reticulum?
- a network of flattened sacs running through the cytoplasm of eukaryotic cells
what is transported through the endoplasmic reticulum?
- molecules, particularly proteins can be transported through the cells inside the sacs separate from the rest of the cytoplasm
where is nucleolus found
in the nucleus, one or more may be present
function of nucleolus?
- to make ribosomes using the information in its own DNA
what is the form of RNA used in manufacture of ribosomes?
tRNA
which component contains tRNA for ribosomes?
nucleolus
- from one or more chromosomes
- nucleolus contains genes for making tRNA
describe the components around the nucleolus core
- less dense region
- ribosomal subunits are assembles
- combines rRNA with ribosomal proteins imported from the cytoplasm
- the more ribosome a cell makes, the larger its nucleus
the different parts of the nucleolus? ..
.. only come together during the manufacture of ribosomes
- they separate during nuclear division
the membranes of endoplasmic reticulum form..?
flattened compartments called sacs or cisternae
what happens at ribosomes?
protein synthesis
why does rough er look rough?
covered with many tiny organelles called ribosomes
function of smooth er?
- makes lipids and steroids, such as cholesterol, and oestrogen and testosterone
- storage site for calcium ions which are involved in muscle contraction
why is smooth er abundant in muscle cells
- storage site for calcium ions which are involved in muscle contraction
why smooth er present in liver?
- drug metabolism
how to observe ribosomes?
- electron microscope (can see two subunits, one large one small)
(LM cannot)
units used for ribosomes
S units (svedberg)
- S units are a measure of how of how rapidly substances sediment in a high speed centrifuge (ultracentrifuge).
- ^ sediment, ^ s unit
S units for ribosomes in eukaryotes and prokaryotes?
- Eukaryotes 80s
- Prokaryotes 70s
why ribosomes in mitochondria and chloroplasts contain 70s ribosomes?
- bcs of their prokaryotic origins
what are ribosomes made of?
equal parts ribosomal RNA (rRNA) and protein
what are the interacting molecules in protein synthesis in the ribosome?
- mRNA
- tRNA
- amino acids
- regulatory proteins
compare animal cell and plant cell vacuoles
- AC : some are phagocytic (temporary) and small, some not present at all
- PC : they are large, centralized and permanent
why are plant cells larger in size than AC
presence of vacuoles
function of nucleolus?
manufactures ribosomal RNA to assemble ribosome
how are ribosome subunits formed?
- rRNA is synthesized from DNA
- protein assembled with rRNA form large and small subunits ribosome
- subunits exit nuclear pores to cytoplasm
function of vacuoles?
- regulates osmotic properties of cells
- storage for pigments and organic compounds
function of tonoplast?
- membrane which controls exchange content
enzymes, pigments , sugars / organic compunds , mineral salts , gases
what are microtubules made of?
tubulin - alpha-tubulin - beta-tubulin tubulins form to make a dimer dimers join to make protofilaments (controlled my microtubule organising centres [MTOC])
function of microtubules
- structural cell component
- intracellular transport system
