Cell Organisation Flashcards
Structure of prokaryotic cells
Contain no nucleus
No cell membrane
DNA/RNA is located in cytoplasm
Contains a cell wall
Divides through binary fission (rapid mitosis)
Structure of eukaryotic cells
Contain a nucleus & membrane bound organelles
Only plants & fungi contain a cell wall
Division involves mitosis
What is a cell membrane
A flexible, semi-permeable membrane (phospholipid bilayer) that separates the cells external & internal environment
Transmembrane proteins (emdedded in cell membranes) help to perform
Movement of substances in/out of cells
Immunological identity (helps immune system to recognise our own cells)
Receptors (recognition site for
hormones)
What is a cell junction
Contact/communication points between adjacent cell membranes of tightly packed cells
Examples of tight junctions
Found in stomach, intestines & bladder
Where the transmembrane protein fuse cells together to reinforce the junctions & seal off passageways to prevent leaking
Examples of gap junctions
Small fluid-filled tunnels between neighbouring cells
Nerves
Which body cells do not have a nucleus
Red blood cells
What does the nucleolus produce
RNA (Ribonucleic Acid)
What are chromosomes
Thread-like structures of nucleic acids & proteins found in the nucleus of most living cells, carrying genetic information
Coiled up DNA
How many chromosomes are in each cell in the body (apart from gametes)
46
How many chromosomes are in gametes
23 pairs
What are the two pairs of male & female gametes
Male - XY
Female - XX
Why are males more likely to develop genetic diseases
If there is a disease on the single X chromosome, the Y cannot counteract it unlike female gametes
What are histones
Proteins that DNA form a double helix around
What is the meaning of epigenetics
Where enviornments can impact which genes are switched on
What is the cytoskeleton
A network of protein filaments that extends through the cytosol
What do the protein filaments in the cytoskeleton assist
Help cells generate movement eg enables white blood cells to migrate to sites of injury
In muscle cells they are the organelle that enables muscle contraction
Physical support & shape
Assists in cell division
What is ATP
Adenosine Triphosphate - the energy currency of somatic cells
What processes do mitochondria undergo
Use oxygen & nutrients such as glucose to create ATP via aerobic respiration
What are ribosomes
The sites of protein synthesis containing high quantities of RNA
They are either free ‘mobile’ in cytoplasm or bound to rough endoplasmic reticulum
the difference between free ribosomes & stationary
Free ribosomes make protein for inside the cell whereas those on the rough endoplasmic reticulum make proteins for outside the cell
What is the Endoplasmic Reticulum (ER)
A network of membranes in the form of flattened sacs which extends from the nucleur envelope throughout the cytoplasm to the cell membrane
Endoplasmic- within plasma
Reticulum- network
Compare the two types of ER
Rough ER is continuous with the nucleur membrane & its outer surface is studded with ribosomes which synthesises & transports proteins
Smooth ER contains no ribosomes but instead unique enzymes which perform lipid & hormone synthesis, in the liver enzymes detoxify & in muscle it releases calcium for contraction
What is the function of the golgi apparatus
Modifies, sorts, packages & transports proteins received from the rough ER
Enzymes modify the proteins & they bud off in transport vesicles
It consists of flattened membranous sacs & most cells have several Golgi
What is the function of lysosomes
Vesicles that contain as many as 60 powerful enzymes which can breakdown a variety of molecules
They recycle worn out organelles by engullfing, digesting & returning components to the cytosol for reuse
Also used to digest foreign cells
And release enzymes externally eg with sperm to assist egg entry
Lyso- breakdown
Soma-body
Process of mitosis
Full set of chromosomes is first duplicated & then evenly distributed into both daughter cells
1 division creating 2 identical diploid daughter cells
Used for growth & repair
But we are Born with a set number of brain & muscle cells & egg cells which cannot undergo mitosis
Process of meiosis
Gametes produce 4 haploid nucleus (half) cells through 2 divisions
The 4 cells produced are non-identical
What is a zygote
Diploid cells which have 2 copies of chromosomes (23 pairs)
Zygote leads onto undergoing mitosis which develops into an embryo & eventually a foetus
The four amino acids in DNA sequences
Adenine
Cytosine
Thymine
Guanine
The two phases of protein synthesis
- Transcription - copy of one gene made into mRNA (messenger RNA) which travels out of the nucleus to a ribosome
- Translation - ribosomes read the code & produces a chain of amino acids to form the required protein
(If protein used within cell distributed by free ribsomones, if outside of cell by the Golgi)
Passive transport of molecules & examples
Movement of substances from an area of HIGH - low concentration (moving down the conc gradient) & requires no energy
Eg
Diffusion ie gases
Osmosis
Facilitated diffusion
Active transport of molecules & examples
Movement of substances from an area of LOW - high concentration (up the conc gradient) & requires ATP energy
Egs
Pumps (sodium potassium pump)-
Endocytosis
Exocytosis
What is pinocytosis
Specialised cells that drink fluids
What is diffusion
Movement of molecules down the conc gradient such as gases eg oxygen
What is osmosis
Movement of water down the conc gradient
Dilutes concentrated & concentrates diluted
What is facilitated diffusion
Movement down the conc gradient aided by transmembrane proteins
For larger substances eg glucose & charged molecules
What are active transport pumps
Use protein pumps in the cell membrane to allow specific molecules up the conc gradient
Sodium potassium pump important for nerves
What is endocytosis
Engulfing of particles into the cell through cell membrane extensions
Either phagocytosis or pinocytosis
What is exocytosis
Removal of waste from the cell
Fuses with membrane before being expelled
