What is every organism composed of?
What are cells?
The functional unit of all living things
Why are cells small?
To increase their surface area to volume ratio
What are the two types of cells?
What is a prokaryotic cell?
Cells that do not have a membrane bound nucleus
What is a eukaryotic cell?
Cell that consists of a cytomplasm and a defined nusleus bound by a nucleus membrane
What are some properties of prokaryotic cells?
Found in bacteria
No nuclear membrane
No membrane bound structures
What are some properties of eukaryotic cells?
Found in human cells, multicellular animals and plants
Nucleus with membrane
Membrane bound structures
What are stem cells?
Undifferentiated cell which are capable of giving rise to indefinitely more cells of the same type
What are the two types of stem cells?
What are pluripotent stem cells?
Can differentiate into all cell types of the body
What are multipotent stem cells?
Can differentiate into many cell types
What do all cells contain a complete set of?
What determines which proteins are found within a cell?
The genes within the DNA that are being expressed
What are genes?
Sequence of DNA or RNA that codes for a molecule that has a function
What happens during differentiation?
Cells pass through a series of changes where changes in gene expression are reflected by alterations of the cells structure and behaviour
What is differentiation?
Cells change from one cell type to another by expressing certain genes
What properties do cancer cells have?
Divide without any control
Fail to coordinate with normal cells
Fail to differentiate into specialised cells
Displace and replace normal cells
What are the processes of cell death?
What is apoptosis?
Physiological, programmed cell death
What is necrosis?
Pathological cell death caused by injury or disease
What is the process of apoptosis?
- Individual cells are induced to die
- Membrane bleb, causing no damage to surrounding cells
- Within hours there is no inflammation
What is the process of necrosis?
- Groups of cells are induced to die
- Membrane ruptures causing damage to surrounding vessels
- Within days there is inflammation
What are the four types of tissues?
What are organs?
Mixture of different tissues
What are systems?
Cells or organs with similar functional roles
What are cell organelles?
Internal organs of a cell responsible for carrying out specific jobs
What are some examples of cell organelles?
Nucleus (containing nucleolus)
What is mitochondria?
Produce a cells source of ATP
What are properties of mitochondria?
Outer membrane contains pores (proteins responsible for high permeability)
Inner membrane has cristae (fold increase surface area to fit in more proteins)
Matrix contains binding sites for calcium and most enzymes for oxidation of food molecules
Synthesise most of their own proteins, self replicate, own ribosomes and their own circular DNA
What is the nucleus?
Usually largest organelle, main function is to reunite ribosomal RNA (rRNA) and combine it with proteins, occuring in the nucleoli
What are some properties of the nucleus?
Contains DNA, nucleoproteins and some RNA
DNA tends to be in two forms (heterochromatin - tightly coiled inactive chromatin, or euchromatin - open chromatin)
Chromatin is a mass of genetic material composed of DNA
What is the nuclear envelope?
Surrounds the nucleus and contains the genetic material?
What are some properties of the nuclear envelope?
Made of phospholipid bilayer
Closely associated with the endoplasmic reticulum
What is the endoplasmic reticulum?
Network of tubules continuous from the nuclear envelope which packages up proteins
What are the two components of the endoplasmic reticulum?
Rough ER, has ribosomes attatched
Smooth ER, used to breakdown compounds (such as glucose) or synthesise compounds (such as lipids)
What is the golgi apparatus?
Complex of vesicles and folded membranes involved in secretion and extracellular transport
Proteins are packaged into vesicles destined for lysonomes, secretory vesicles or the cell surface
What are lysosomes?
Packaged up with proteins in a vesicle
What are properties of lysosomes?
Contains degradative enzymes
Primary lysosome mixes with phagosomes (vesicle containing substance from phagocytosis) to produce secondary lysosomes which release inside or outside the cell
Used to seperate enzymes from the rest of the cell
What are ribosomes?
The site of protein synthesis
What are the properties of ribosomes?
Link amino acids together in the order specified by mRNA
Small ribosomal subunit reads the RNA
Large ibosomal subunit joins amino acids to form polypeptide chain
What is the cytoplasm?
Material within a living cell excluding the nucleus, compromises of the cytosol and the organelles
What is the cytosol?
Liquid found inside cells, also known as intracellular fluid (ICF)
What are the purposes of the cytoskeleton?
Supports and maintains cell shape
Hold organelles in position
Interacts with extracellular structures to hold the cell in place
Involved in cytoplasmic streaming
What are the three main proteins that the cytoskeleton is composed of?
Microfilaments (made up of strans of protein actin, interacts with strands of other proteins)
Intermediate filament (made up of fibrous proteins organised into tough assemblages that stabilise a cells structure)
Microtubules (long hollow cylanders made up of protein tubulin, consists of two subunits a-tubulin and b-tubulin)
What are celia and flagella made up of?
Microtubules which are projected from the cell to move molecules
What is the cell membrane?
Semi permeable membrane surrounding the cytoplasm of a cell
What are properties of the cell membrane?
Composed of phospholipid bilayer
Embedded with proteins for functionality
Are membrane lipids amphipathic?
What does amphipathic mean?
Has both hydrophobic and hydrophillic parts
What parts of the cell membrane is hydrophobic and hydrophillic?
Phospholipid heads are hydrophillic and the tails are hydrophobic
What are the different ways that proteins can be associated with the cell membrane?
Spam the membrane
Embedded and tunnel all of the way through
Embedded and tunnel part of the way through
What are some functions of the cell membrane?
Acts as a selective barrier
Transport (proteins provide channels)
Receptor (change conformation and initiate chain of reactions)
Attatchment to the cytoskeleton and extracellular matrix (ECM)
What are the two forms of transport?
What are the two types of diffusion?
Passive diffusion (concentration gradient needed, lipid soluble molecules pass freely unless to large)
Facilatated diffusion (concentration gradient needed, requires carrier molecules)
What are the two forms of active transport?
Endocytosis (cell taking in matter)
Exocytosis (vesicle contents secreted outside of cell)
What is cells sticking together called?
What are different types of cell adhesion?
Tight junction (physical barrier to diffusion between cells, examples are kidney, intestine and blood brain barrier)
Adhesive junction (adherens junction - link actin filaments in two different cells, desmosomes - link keratine filaments in two different cells)
Gap junction (form channels between cells, link the two cells cytoplasm, example being pancreas, liver and heart muscle)
What can disease do to cell adhestion?
Stop them sticking together and cause them to seperate, as seen in cancer
What are some examples of cell signalling?
Contact dependent (membrane bound signal molecule)
Paracrine (cell realeases molecule to cells around it)
Synaptic (nervous signals target cells using neurotransmitter)
Endocrine (hormones travelling through blood to target cell)
What does a receptor do?
Recieves a molecule and then triggers a series of pathways in response
Where are some places you can find receptors?
On the cell membrane or in the cytoplasm