Summarise the 4 key points of the cell theory
1. Cell is the basic structural unit of living organisms
2. Organism activity depends on the activity of the cells
3. Biochemical cell activities are dictated by their specific
sub-cellular structures
4. The continuity of life has a cellular basis
Explain a generalised cell
1. Has a plasma membrane (boundary of the cell)
2. Has a cytoplasm, fluid packed with organelle that perform
specific functions
3. Has a nucleus that controls cellular activity.
Name the basic structure that cellular membranes share
1. Phospholipid bilayer with embedded proteins
Why do the phospholipids form a tail to tail connection in a aqueous environment
1. Hydrophobic tail regions of the lipid bilayer attract towards each
other as they are non polar
2. Hydrophillic polar heads orientate towards the aqueous
intracellular fluid (cytoplasm) and extracellular fluid.
What is the importance of glycocalyx in cell interactions?
1. The sugar residues of the glycocalyx provide recognisable
biological markers for cells to recognise each other.
For example a sperm can recognise an ovum by it's unique glycocalyx
Which two types of cell junction would you expect to find between
muscle cells of the heart?
1. Gap junctions (communicating junctions) that allow ions to flow
between the cardiac cells.
2. Desmosomes (anchoring junctions) that secure cardiac cells
together as the heart beats
What is the energy source for all types of diffusion?
1. Diffusion is driven by kinetic energy of the molecules. No ATP is
necessary for this to occur.
2. Kinetic energy refers to the potential energy stored within molecules
What determines the direction of any diffusion process
1. The relative concentration of substances in different areas
determines the direction and type of diffusion and wether it requires
cellular energy or not.
2. Diffusion occurs from an area of high concentration to an area of
low concentration.
3. Osmosis is described as the movement of water across a
semipermeable membrane from an area of high concentration to an area
of low concentration. This is going down the concentration gradient.
What are two types of facilitated diffusion and how to they differ?
1. Channel mediated diffusion, the diffusing substance moves through
a membrane channel
2. Carrier mediated diffusion, the diffusing substance attaches to a
membrane protein carrier that moves it across the membrane.
How does the Sodium Potassium pump work?
1. When 3 Na+ ions from the inside of the cell bind to the sodium
potassium pump it needs ATP to pump those ions against it's
concentration gradient as Na+ and Cl+ ions are in higher concentration
outside the cell.
2. ATP attaches one of it's phosphate groups to the pump which
releases the Na+ ions outside of the cell.
3. 2 K+ ions from the outside of the cell attach themselves to the
gated pump, this causes a conformational change in the pump, the
phosphate group releases it's self back into the cytoplasm and the K+
ions are pumped into the cell going against the concentration gradient.
4. This process requires ATP to work because going from a low area
of concentration to a high area of concentration takes more work than
going from high to low.
When the cell membrane expands during cell growth does the process
involve endocytosis or exocytosis.
1. The membrane expanding involves exocytosis.
What do phagocytic cells do? and what type of transport is described?
1. Phagocytic cells engulf debris.
2. Phagocytosis is a type of vesicular transport
Which type of vesicular transport allows a cell to take in
cholesterol from the ECF and does this process require ATP?
1. Receptor mediated endocytosis allows the intake of some hormones,
ions, cholesterol and most marco-molecules.
2. This process requires ATP
Which process establishes the resting membrane potential?
1. Diffusion of ions, mainly the diffusion of K+ from the cell
through leakage channels establishes the resting membrane potential.
Is the inside of the plasma membrane negative or positive, relative
to it's outside in a polarised membrane?
1. In a polarised membrane the inside is negative relative to it's outside.
What term is used to indicate signalling chemicals that bind to
membrane receptors? Which type of membrane receptor is most important
in directing intracellular events by promoting formation of second messengers.?
1. Signalling chemicals that bind to membrane receptors are called ligands
2. G-Protein linked receptors direct intracellular events by
promoting formation of second messengers
Which organelle is the major site for ATP synthesis?
1. Mitochondria
What are 2 organelles and one inclusion involved in protein synthesis
(translation) and how to these organelles interact in that process?
1. Rough Endoplasmic Reticulum (organelle) provides a site for
ribosomal attachment, it's cisterns package the newly translated
proteins in vesicles for transport to the Golgi body.
2. Ribosomes (inclusion) are the main site of protein
synthesis(translation) they are combined of a small and large subunit
made up of proteins and ribosomal RNA.
3. The Golgi body (organelle) made of flat membraneous sacs modifies
and packages it receives and sends them to various destinations within
or outside the cell.
Compare the functions of Lysosomes and Peroxisomes
1. Lysosomal enzymes digest foreign substances engulfed by the cell,
non useful or dead organelle, to prevent the build up of cellular debris.
2. The enzymes in peroxisomes detoxify harmful chemicals (H2O2) into
H2O, and neutralise free radicals.
How are Microtubules and Microfilaments(actin filaments) functionally related?
1. Both Microtubules and Microfilaments are involved in organelle
movement transport and movement of the cell itself.
Which component of the cytoskeleton is most important for maintaining
cell shape?
1. Intermediate filaments
What is the major role of microvilli?
1. Microvilli is found in the linings of the intestine and it's main
role is to increase the area of the cell surface for absorption of
nutrients and substances
What happens if a cell were to lose their nucleus?
1. The cell is doomed to die because it is unable to produce proteins
which include the enzymes needed for all metabolic reactions
What is the role of the nucleoli?
1. Nucleoli are the site of 'ribosomal biogenesis'
What is the role of histones in the nucleus?
1. Histone proteins provide the means to pack DNA in a compact
orderly sequence and they play a role in gene regulation.
If a DNA strand reads CGAATG what is the base sequence of the
corresponding DNA strand
1. GCTTAC
During what phase of the cell cycle if DNA synthesised?
1. DNA is synthesised during the S phase.
What are three events occurring in prophase that are undone in telophase?
1. The nuclear envelope breaks up
2. The mitotic spindle forms
3. Nucleoli disappear and the chromosomes coil and condense
How to codons and anticodons differ?
1. Codons are 3 base sequences in mRMA which each specifies an amino acid.
2. Anticodons are 3 base sequences in tRNA that are complimentary to
the codons specifying the amino acid they transport to the ribosome
during translation.
What is the role of DNA in transcription?
1. DNA provides coded instructions for protein synthesis via the mRNA
synthesised in it.
What is apoptosis?
1. The process of programmed cell death which rids the body of cells
that are stressed, damaged, old or no longer needed.
What is Anaplasia?
1. Abnormalities in cell structure and loss of differentiation for
example cancer cells typically lose the appearance of the parent cells
and come to resemble undifferentiated or embryonic cells.
What is Dysplasia
1. A change in cell size, shape, or arrangement due to chronic
irritation, inflammation.
What is Hypertrophy?
1. Growth of an organ or tissue due to an increase in the size of its
cell. Hypertrophy is a normal response of skeletal muscle cells when
they are challenges to life excessive weight.
What are liposomes?
1. Hollow microscopic sacs formed of phospholipids that can be filled
with a variety of drugs. Serve as multipurpose vehicles for drugs and
genetic material.
What is mutation?
1. A change in DNA base sequence that may lead to incorporation of
incorrect amino acids in particular positions in the resulting
protein; the affected protein may remain unimpaired or may function
abnormally or not at all leading to disease.
What is necrosis?
1. Death of a cell or group of cells due to injury or disease. Acute
injury causes the cells to swell and burst, and induces the
inflammatory response, this is uncontrolled cell death.