Topic 1 Flashcards
list in order from smallest to largest the levels of organisation
chemical/molecular level cellular level tissue level organ level organ system level the organism level
define the molecular level
contains atoms (smallest unit of matter), molecules such as ions, proteins, carbs, lipids and nucleic acids.
function - structure/function, storage, messengers, control
define the cellular level
a group of atoms, molecules and organelles working together, forms the basic unit of life.
define the tissue level
a group of similar cells working together
4 main types of tissue - epithelial, connective, muscle and neural.
define the organ level
made up of different tissues
(organ is a group of tissues)
organ functions are supplied by the tissues, there are multitasking tissues and specialist organs.
define organ system level
an organ system is a group of organs working together.
humans have 11 organs with various functions
define the organism level
all the organ systems working together to form a functional organism.
define a cell
the basic unit of life, structural and functional unit of the body.
they can undertake metabolic reactions, maintain homeostasis, reproduce themselves and communicate
what are the three main parts of a cells construction
- plasma membrane
- cytosol
- nucleus
describe the structure of the phospholipid bilayer
lipid bilayer
- phospholipids 70%
- cholesterol 20%
- glycolipids 5%
two phospholipids layers with fatty acid tails in the center (hydrophobic tails) and hydrophilic heads.
it is flexible/fluid - the fluid mosaic membrane is a constantly moving sea of lipids with a mosaic of proteins - lipids and many proteins can rotate and move sideways in their half so it is not rigid.
what does flexibility depend on the membrane?
depends on two things:
- number of double bonds in fatty acid tails and cholesterol.
more double bonds = more flexible
more cholesterol at body temp = less flexible
more cholesterol at low temp = increases fluidity.
why is it important for the membrane to be flexible?
a flexible membrane allows self-sealing if it penetrated, allows movement during cell division and secretion of substances (helps to import and export substances if needed).
what are the functions of the cell membrane
- acts as a barrier separating inside and outside.
- controls the flow of substances into and out of the cell.
- helps identify the cell to other cells such as immune cells.
- participates in intercellular signaling.
list all the cellular organelles
nucleus ribosomes endoplastic reticulum - rough and smooth golgi apparatus mitochondria chloroplast vacuole centriole centromere cytoskeleton lysosome flagellum cilia, microvilli and flagella peroxisomes proteasomes
what is the cytoplasm
contains the cytosol and other organelles
where most cellular activities occur such as metabolic pathways including glycolysis and processes such as cell division.
what are organelles
small individual structures within the cytoplasm that have various functions
what is the difference between membrane bound organelles and non membrane organelles
organelles without membranes have more functioning with structural support or moving substances within cells but membrane bound organelles allow specialised functions to be performed within them,
what is the cytoskeleton
is a network of three filaments types (proteins) in cytosol.
it helps maintain cell and organelle shape and structure, generate movement.
functions as a scaffold that helps determine a cells shape and organise the cellular contents and aids movements of organelles within the cell, of chromosomes during cell division and of whole cell such as phagocytes.
describe the three types of filaments
microfilaments - thinnest, actin, myosin, help generate movements.
e.g. white blood cells moving into tissue.
intermediate filaments - intermediate size, made of several proteins, very strong, stabilise organelle position, found where cell subjected to stress.
microtubules - largest (tubulin) grow from centrioles, move organelles and secretory vesicles and chromosomes.
what are centromeres
located near the nucleus, it consists of a pair of centrioles and pericentriolar material.
function - the pericentriolar material of centrosome contains tubulins that build microtubules in nondividing cells.
that pericentriolar material of the centrosome forms the mitotic spindle during cell division.
peri = around
what are cilia, flagella and microvilli
are extensions of the cell membrane that are supported by the cytoplasm
cilia - short hair like projections, extend from cells surface: beat in a coordinated manner in order to sweep away substances. appear in clusters.
flagella - long projections that propel an entire cell; only in sperm
microvilli - finger like projections from the cell membrane, greatly increase surface area of a cell.
what are ribosomes
composed of rRNA and proteins in large and small subunits, made in nucleus; join together in cytosol.
site of proteins production
ribosomes on rough endoplasmic reticulum (RER) make proteins for the cell membrane or secretion out of the cell.
what is the endoplasmic reticulum
flat, folded, membranous sacs attached to nuclear membrane.
two types:
- rough
- smooth
what is RER
continuous with nuclear membrane, has ribosomes attached, synthesizes membrane protein, secretory proteins and organelle proteins that are transferred into organelles, inserted into the plasma membrane or secreted during exocytosis.
what is the SER
extended from RER, synthesises fatty acids and steroid hormones, detoxifiers lipid soluble drugs.
the sarcoplasmic reticulum is a type of smooth endoplasmic reticulum in muscle, stores calcium ions needed for muscle contraction to occur (when muscles needs to be relaxed, Ca ions are stored).
what is the golgi complex
modifies, sorts, packages and transports proteins received from rough ER.
forms secretory vesicle that discharge processed proteins via exocytosis into extracellular fluid, forms membrane, forms transport vesicle that carry molecules to other organelles, such as lysosomes.
what are lysososmes
Vesicle containing digestive and hydrolytic enzymes (pH 5)
Reasonably acidic because enzymes are breaking substances that have been brought into cell.
Function:
Digest substances that enter a cell via endocytosis and transport final products of digestion into cytosol.
Carry out autophagy, the digestion of worn out organelles.
Implement autolysis, the digestion of an entire cell.
Accomplish extracellular digestion.
Sperm lysosomal enzymes digest their acrosome (protective cap) for fertilisation to occur.
what are peroxisomes
Small vesicles containing enzymes to break down toxic molecules formed during metabolism or ingestion. Eg; alcohol, hydrogen peroxide, (H2O2), superoxide.
Don’t have the digestive enzymes that lysosomes do.
what are proteasomes
Tiny stack of four protein rings around a central core containing proteases (protein digesting enzyme).
Destroy unneeded or faulty proteins in biochemical pathways after they have performed their function.
Break proteins into peptides, other enzymes break peptides into amino acids (recycles into new proteins).
what is the mitochondria
Generates ATP through reactions of aerobic cellular respiration.
Play an important early role in apoptosis.
what is the nucelus
Largest organelle surrounded by a nuclear (double) membrane with pores.
Most cells have one nucleus. Red cells have none; skeletal muscle cells have multiple.
Command and control centre of cell:
Controls cell structure, directs cell activities, produces ribosomes in nucleoli.
Contains DNA in 23 pairs of chromosomes. Genes code for a specific protein or enzyme.
Function:
Controls cellular structure
Directs cellular function
Produces ribosomes in nucleoli.
explain cell ageing
As cell structure and function change, homeostatic responses decline – body more vulnerable to disease, infection, environmental stressors.
Some body cell types nerve divide. Eg; skeletal and cardiac muscle cells, most neurons or have limited capacity to undertake mitosis.
Outcome of both: damaged cells will not/ may not be replaced – reduction in function of tissue/organ.
“Ageing genes” (normal genes important for cell function) reduce in activity as we age – slows down vital cell processes.
Telomeres: protective DNA “cap” on chromosomes ends; typically get shorter each cell division.
High stress level – shorter telomere length.
Glucose – added randomly to proteins which causes irreversible cross linking of adjacent proteins – loss of elasticity – stiffness in tissues.
Increased autoimmunity – as membrane protein changes increase, cell identity markers may be affected. Altered cell identity markers eg MHC proteins may – antibodies which bind to the membrane – cell destruction. As protein changes to increase, autoimmune response increase – loss of tissue and reduction in function.
