cc2 - cell structure and organisation

animal cell structure

plant cell structure

nucleus

function: contains DNA to synthesise proteins

structure: surrounded by a double membrane called the envelope containing pores to allow the entry and exit of RNA and proteins. also contains chromatin and a nucleolus which is the site of ribosome production.

mitochondria

function: site of most aerobic respiration, which produces ATP which provides energy for cells reactions.

structure: oval shaped, bound by a double membrane called the envelope, between the membranes is filled with fluid. Inner membrane is folded to form cristae (where most of ATP is produced). Inside this is the matrix which contains chemical compounds such as protein, lipids and traces of DNA.

rough endoplasmic reticulum

function: site of protein synthesis and processing/transport

structure: studded with ribosomes, flattened cisternae, continuous with nuclear membrane

smooth endoplasmic reticulum

function: site of phospholipids and the packaging of proteins into vesicles

structure: long network of long, tube-like structure, lacking ribosomes

golgi body

functions: transportation and modification of proteins, secreting enzymes and carbohydrates, transportation and storage of lipids, forming lysosomes

structure: formed by rough ER pinching off at the end to form vesicles which fuse together. made up of cisternae held together by matrix proteins

prokaryote

single celled organism lacking membrane bound organelles including a nucleus, DNA is free in the cytoplasm (bacteria and archaea)

what are eukaryotes?

organisms containing cells that have membrane bound organelles, DNA is contained in chromosones (fungi, plants and animals)

what is a virus’ role and structure?

An acellular invader that takes over a cell’s metabolism and multiplies. It consists of a nucleic acid (DNA or RNA) surrounded by a protein coat (capsid). Can be crystallised but also reproduces so uncertainty whether it is alive or not.

generalised bacteria cell

no nuclus, mesosome site of aeribic respiration, has plasmids, 70S ribosomes, cell wall, flagellum, cytoplasm and occasionly slime coat

role of lysosomes

bud off the Golgi body, contains digestive enzymes that are activated when it fuses with a vesicle containing an unwanted substance

secretory vesicle

buds off the Golgi body, contains modified proteins, fuses with cell membrane to exit the cell by exocytosis

centrioles

found in animal cells, located just outside of the nucleus in the centrosome, two hollow tubes at right angles to each other, divide and move to opposite sides during cell division where they synthesise the microtubules of the spindles which separate chromosomes

permanent vacuole

found in plant cells, large permanent fluid-filled sacs, single membrane called tonoplast, stores chemicals, takes in water through osmosis to help cell rigidity

cell wall

plant cells only, made of cellulose, provides strength, fully permeable, contains pores

cell differentiation

process of cells becoming specialised for different functions

tissue

an aggregation of similar cells carrying out the same function

epithelial tissue

continuous layer, covering or lining the internal and external surfaces of the body, don’t have blood vessels, sit on basement membrane - made of collagen and protein, often have a protective or secretory function

cuboidal epithelium

simplest, cube-shaped cells, 1 cell thick, can be found in the proximal convoluted tubule of the kidney nephron and ducks of salivary gland

columnar epithelial

elongated cells, cilia where substances move, found in trachea and oviduct (fallopian tube)

squamous epithelial

flattened cells, line the Bowman’s capsule of the kidney nephron

endosymbiotic theory

proposes that eukaryotic cells originated through a symbiotic relationship between different species of prokaryotes; suggests that certain organelles, such as mitochondria and chloroplasts, were once free-living bacteria that were engulfed by a host cell.

connective tissue

connects, supports or separates tissues and organs, contains elastic and collagen fibres, between are fat-storing cells (adipocytes) and immune system cells, e.g. blood, bone and cartilage

skeletal muscle tissue

attached to bones, generates locomotion (movement) in mammals, long cells/fibres with powerful contraction, controls voluntary movements, striped/striated cells under microscope

smooth muscle tissue

individual, spindle-shaped cells that contact rhythmically, occurs in skin, walls of blood vessel and digestive + respiratory tracts, controls involuntary movements, unstriped/unstriated under microscope

cardiac muscle tissue

only found in heart, structure is in between smooth and skeletal - has stripes but no long fibres, controls involuntary movements, contracts rhythmically with no stimulation from nerves / hormones

organ

a group of tissues in a structural unit working together and performing a specific function

organ system

a group of organs working together as a single unit to carry out a specific function for the whole organism

nuclear pores

allows exit of mRNA and ribosomes

role of the nuclear envelope

separates contents of nucleus with cytoplasm

what does the nucleolus produce?

mRNA, tRNA and ribosomes

chromatin role

condenses before cell division to form chromosomes

plasmodesmata

connects cells with canals filled with cytoplasm, allows transport via the symplastic pathway