Cell Structure Flashcards
What are the 3 different types of cell?
prokaryotic, eukaryotic, akaryotic
What are prokaryotes?
all bacteria
what are eukaryotes?
animals and plants
what are akaryotes?
all viruses (non-cellular or acellular)
What are the 2 types of microscope?
Light microscope and electron microscope
What is resolution?
the ability to see objects as separate from one another
What is the resolution of a light microscope?
about 0.2 micrometres (μm)
What is the resolution of an electron microscope?
0.1 nanometres (nm)
What is the conversion of nanometres to micrometres
1,000 nm = 1μm
What is the conversion of micrometres to millimetres?
1,000μm = 1mm
What is the conversion of millimetres to centimetres?
10mm=1cm
What is the conversion of centimetres to metres?
100cm=1m
What are internal cell membranes?
the membranes of organelles
What are the general functions of internal cell membranes?
Providing a transport system, allowing substances in or out
Separating areas from the rest of the cytoplasm (compartmentalisation)
providing a large surface area for attachment of enzymes and other reactants
What is another function of the internal cell membranes of mitochondria?
ATP synthesis
What is the function of the plasma membrane?
controls entry and exit of substances in and out of cells
What is the function of the golgi body?
packages and modifies proteins prior to secretion
What is the function of the nucleus?
contains chromatin and controls activities of the cell
What is the function of the nuclear envelope?
barrier between nucleus and cytoplasm
has nuclear pores
What is the function of the nucleolus?
site of ribosomal RNA synthesis
What is the function of the rough endoplasmic reticulum?
site of protein synthesis
What is the function of the smooth endoplasmic reticulum?
site of lipid and steroid synthesis
What is the function of the lysosome?
contain hydrolytic enzymes used in secretion and phagocytosis
break down excess or worn out cell parts, attack virus/bacteria
What is the function of the mitochondrion?
energy release ? ATP production during cell respiration
What is the function of the ribosomes?
protein synthesis and transport
What is the function of the centrioles?
used in spindle formation in cell division
What is the function of the chloroplast?
site of photosynthesis
What is the function of the plant cell vacuole?
storage site in plant cells
What is the function of the tonoplast?
surrounds the plant cell vacuole
What is the function of the cell wall?
prevents bursting of plant cells due to osmosis
What is the function of the plasmodesmata?
cytoplasmic connections between adjacent plant cells
What is a vesicle?
a membranous fluid filled sac in a plant or animal cell
What is exocytosis?
when a cell releases substances when a vesicles membranes fuses with the plasma membrane
What is chromatin?
uncoiled chromosomes
composed of DNA and protein (histones)
What are plasmids?
small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. most common in bacteria in circles
What are mesosomes?
Folded invaginations in the plasma membrane of bacteria
What is Circular DNA?
one conformational arrangement of DNA where it attains a closed structure
What are 70S ribosomes?
smaller ribosomes that are found in prokaryotes (bacterias) and cell organelles (mitochondria and chloroplasts)
What are 80S ribosomes?
larger ribosomes that are exclusively found in eukaryotic cells
What do viruses consist of?
only a protein coat enclosing nucleic acid (either DNA or RNA)
What is the structure of the plasma membrane?
consists of an ‘electron transparent’ layer sandwiched between 2 ‘electron-dense’ layers.
about 7-8nm thick
What are the structural components of the fluid mosaic model?
Phospholipids (phospholipid bilayer)
Transmembrane proteins (can be facilitated diffusion channels)
integral proteins
glycoproteins with carbohydrate side chain
What do phospholipids have?
a hydrophilic head
a hydrophobic tail
How are phospholipids arranged?
in a bimolecular ‘bilayer’
What other molecules are in the phospholipid bilayer?
cholesterol
What is the function of cholesterol?
reduces the permeability of the cell membrane so stabilises the membrane
What are structure of proteins in a plasma membrane?
globular
What are some of the functions of proteins in the plasma membrane and how can they be located?
some lie on the surface
some are partly embedded
some extend completely across
can be enzymes
can be involved in membrane transport (carrier proteins)
Where are carbohydrates found in the plasma membrane?
only in the outer layer attached to the phospholipids or proteins (glycolipids or glycoproteins)
What are carbohydrates in plasma membrane involved in?
cell adhesion and cell recognition
What are the main functions of the cell membrane?
structural support
secreting chemicals
cell-cell recognition
taking up nutrients and other requirements
as a semi or partially permeable barrier
How does the membrane act as a barrier for water and solutes?
membrane is permeable to water
selectively permeable to some solutes
Do water-soluble or lipid-soluble substances move through the membrane more easily?
lipid-soluble substances can move through the membrane more easily than water-soluble substances, via the phospholipid portion
Which molecules can move through the membrane freely?
uncharged molecules such as oxygen and carbon dioxide
What does the hydrophobic core of the plasma membrane do?
Impedes the transport of ions and polar molecules
Why can’t ions and large molecules like glucose diffuse across the non-polar centre of the phospholipid bilayer?
they are relatively insoluble in lipid
How do intrinsic proteins enable transport of larger molecules?
in facilitated diffusion channels, down a concentration gradient
What do phospholipids in the membrane do?
allow lipid soluble substances to enter and leave the cell
prevent water soluble substances entering and leaving the cell
make the membrane flexible and self sealing
What are extrinsic proteins?
proteins partially embedded in the membrane. May be enzymes, provide support or be part of receptors
What are intrinsic proteins?
span across the entire membrane. Some ae protein channels, some are carrier proteins
What are protein channels?
water filled tubes allowing water soluble ions across the membrane
What are carrier proteins?
bind to ions or proteins or amino acids. they change shape in order to move molecules across the membrane
What are the functions of proteins?
Structural support
Channels
Active transport
Cell surface receptors for cell-cell recognition
Cell to cell adherence
cell surface receptors for hormones
What does cholesterol do for the membrane?
reduces lateral movement of other molecules including phospholipids
makes the membrane less fluid at high temperatures
prevents leakage of water and dissolved ions from the cell
adds strength to the membrane
Does cholesterol repel or attract water?
it is hydrophobic, so repels water
What are glycolipids made of?
carbohydrate covalently bonded to lipid
What does the carbohydrate part of a glycolipid do?
projects from the cell surface membrane, acting as receptors
What is an example of a glycolipid?
the ABO blood system
What are the functions of glycolipids?
act as recognition sites
help maintain membrane stability
helps cells to attach to each other, forming tissues
What are the functions of glycoproteins?
act as recognition sites
help to attach cells to one another to form tissues
allow cells to recognise each other, for example lymphocytes recognise the organism’s own cells
What are glycoproteins?
carbohydrate chains that attach to extrinsic proteins on the outer surface of the cell membrane
how/what are the molecules that the cell membrane controls movement in and out of the cell? why?
molecules insoluble in lipid cannot easily pass through
large molecules may be too big to pass through
charged molecules (polar) may not be able to get through the phospholipid part
particles with the same charge as the protein channels may be repelled
