cells (topic 2) Flashcards
tissue
a collection of similar cells that perform a specific function
4 types of tissue in animals
nervous tissue - rapid transmission of electrical impulses
epithelial tissue - cover external and internal surfaces
muslce tissue - contracts
connective tissue - holds tissue together, provides strength
5 tissues in plants
xylem tissue - transports water and nutrients from soil to the leaves
phloem tissue - transport and distribute sugars produced by photosynthesis
palisade mesophyll - full of chloroplasts for photosynthesis
spongy mesophyll - packed loosely for gas exchange
epidermis - to protect the leaf
nucleus
- contains cells chromosomes, protein bound linear DNA and controls cell’s activities through production of mRNA, tRNA and rRNA
- lets substances enter/exit eg allows passage of mRNA out the nucleus
nuclear envelope is a double membrane. outer membrane continuous with the endoplasmic reticulum
nucleolus
- manufactures ribosomal RNA and assembles ribosomes
rough endoplasmic reticulum
- protein synthesis
continuous with outer membrane of nucleus.
forms interconnected network of flattened membrane-enclosed sacs called cisternae.
has ribosomes on surface.
smooth endoplasmic reticulum
- synthesises, stores and transports lipids and carbohydrates
lacks ribosomes.
ribosomes
- protein synthesis
found free in the cytoplasm or associated with rough ER.
prokaryotes=70S ribosomes. eukaryotes=80S ribosomes.
two subunits, one large one small (both made of protein and rRNA)
golgi apparatus
- proteins and lipids produced by ER are passed through it
- golgi modifies these proteins eg adds carbs to form glycoproteins
- labels them to be sorted and sent to the correct destination
- transported in vesicles which may move to cell surface and fuse w/ membrane and release contents outside
stack of membranes that make up flattened sacs - cisternae
lysosomes
- hydrolyse material ingested by phagocytic cells
- releases enzymes outside of cell to destroy materials outside of cell
- digests worn out organelles
contains enzymes such as protease, lipase, lysozymes(enzymes that hydrolyse cell wall of bacteria).
lysosomes isolate these enzymes from the rest of the cell before releasing them outside the cell or into a phagocytic vesicle
mitochondria
- site of respiration responsible for production of ATP
‘rod shaped’
double membrane controls entry/exit of materials.
inner membrane folded to form extensions called cristae, large SA for attachment of enzymes/proteins found in the matrix
chloroplasts
- light absorption - carry out photosynthesis
‘disc-shaped’
double membrane = chloroplast envelope
thylakoids contain chlorophyll - provide large SA
thylakoids can be stacked up to 100 to form disc like structures called grana (sg granum)
stroma contains enzymes/proteins needed to make sugars in photosynthesis
contains DNA and ribosomes to quickly manufacture proteins for photosynthesis
vacuoles
- supports plants by making them turgid
- pigments may colour petals to attract pollinators
fluid filled sac bounded by a single membrane (tonoplast)
contains solution of mineral salts, sugars, amino acids, sometimes pigments
cell wall
- provide mechanical strength to plant
- prevents it bursting
- allows water to pass along it
made of microfibrils of cellulose.
thin layer called middle lamella marks boundary between adjacent cell walls + cements them together
prokaryotic cell differences to eukaryotic cells
- smaller
- lack membrane bound organelles
- smaller ribosomes (70S)
- no nucleus, instead single circular DNA molecule free in the cytoplasm, not associated with proteins
- cell wall of murein (a glycoprotein)
also
- may have one or more plasmids
- may have a capsule surrounding the cell
- may have one or more flagella
