cell structure and organisation Flashcards
mitochondria structure
- 5um long
- 2 membranes
- fluid filled intermembrane space, folded inwards = cristae
- circle of DNA
- matrix contains lipids, proteins, enzymes
- 70s ribosomes
- large SA:V
mitochondria function
- ribosomes for protein synthesis
- DNA allows replication
- produces ATP for aerobic respiration
- enzymes for respiration
ribosomes strucutre
- 70s = prokaryote, 80s = eukaryote
- 1 large, 1 small subunit
- assembled in nucleolus from rRNA and protein
- pass out into cytoplasm
ribosomes function
- site of protein synthesis
- read mRNA sequence
- translate genetic code into amino acids which fold into proteins
golgi body strucutre
- fluid filled, flattened sacs
- surrounded by vesicles
features of mitochondria and their significance
- looped DNA = codes for essential proteins in respiration
- 70s ribosomes = translate DNA to produce proteins
- cristae (infoldings) = increase SA of inner membrane
golgi body function
- modify, process, package proteins
- transport and store lipids
- produce secretory enzymes, e.g. lysosome
- secrete carbohydrase for plant cell walls
lysosome structure
- small, temporary vesicles
- single membrane
- contain digestive enzymes
- pinch off golgi body
lysosome function
- digestive enzymes breakdown / recycle cellular waste and unwanted material
nucleolus structure
- spherical structure
nucleolus function
- produces and assembles ribosomes
nucleus structure
- double membrane form nuclear envelope
- pores allow large molecules to leave (mRNA, ribosomes)
- contains DNA
- contains nucleoplasm
- contains nucleolus
what is nucleoplasm?
- granular material in the nucleus
- contains chromatin (coils of DNA)
nucleus function
- controls and regulates activities of the cell
- contains cells genetic material
chromatin structure
- chain of nucleosomes
- coils of DNA that condense into chromosomes
chromatin function
- package DNA into the tight/small space of the nucleus
- condense into chromosomes during cell division
plasmodesmata structure
- fine strands of cytoplasm
- extend through pores in plant cell walls
plasmodesmata function
- facilitate movement of molecules between cells
- allow communication between cells
endoplasmic reticulum strucutre
- double membrane
- flattened sacs with fluid filled spaces (the cristernae)
rough er structure
- series of flattened sacs enclosed by a membrane
- ribosomes on the surface
rough er function
- folds and processes proteins
smooth er structure
- system of membrane bound sacs that lack ribosomes
smooth er function
- synthesis and transport of lipids
centrioles strucutre
- hollow cylinders
- rings of microtubules
- in animals and plant cells (absent in higher plants)
centrioles function
- organise microtubules that make spindle fibres in cell division
chloroplasts structure
- 2 membranes form chloroplast envelope
- fluid filled stroma contains photosynthesis products
- 70s ribosomes
- circular DNA
- chlorophyll found on flattened sacs, thylakoids
- stacks of thylakoids = grana
chloroplast function
- can make proteins and self replicate
- contains photosynthetic pigment to capture sunlight and convert into energy
vacuole structure
- large, permanent fluid filled sac
- bound by single membrane = tonoplast
- sap stores nutrients, water, chemicals
vacuole function
- maintains pressure in plant cells
- supports plant cell walls
- prevents wilting
nuclear envelope strucutre
- double membrane of the nucleus
nuclear envelope function
- prevents genetic material mixing with cytoplasm
RER vs SER
- RER has ribosomes on outer surface (SER doesn’t)
- RER facilitates protein synthesis (SER synthesises lipids)
- RER provides transport (SER provides storage and transport)
chloroplast adaptations for photosynthesis
- granal membrane = large SA
- fluid in stroma contains enzymes and sugars
- chloroplasts have DNA and ribosomes for rapid protein synthesis
how are organelles interrelated?
- nucleus contains chromosomes where DNA encodes proteins
- nuclear pores in nuclear envelope allow mRNA to leave nucleus and attach to ribosomes
- ribosomes contain rRNA transcribed from DNA in nucleolus
- protein synthesis occurs on ribosomes
- polypeptides made on ribosomes move through RER and pack into vesicles that bud of the golgi body
- golgi body produces vesicles containing proteins
- phospholipids and triglycerides move through SER
organelle definition
- specialised structure with a specific function inside a cell
- work together to carry out functions
eukaryotic definition
- distinct nucleus
- membrane bound organelles
- animal or plant cells
- 80s ribosomes
- large SA for enzymes
prokaryotic definition
- single celled
- lack membrane bound organelles
- DNA free in cytoplasm
- reproduce by binary fission
- all life functions in 1 cell
- no mitochondria or nucleus
plant cell wall structure
- cellulose held together into fibres embedded in a matrix
plant cell wall function
- transport: gaps between fibres = permeable to water and dissolved substances.
- mechanical strength: cellulose microfibres are strong and resist expansion
- communication: pores allow strands of cytoplasm (plasmodesmata) to pass, creating the symplast pathway
prokaryotes strucutre
- 70s ribosomes
- cytoplasm
- cell membrane
- cell wall
- DNA in nucleoid region
- small
- single celled
cell wall in bacteria (prokaryote)
- rigid outer covering
- made of peptidoglycan
capsule in bacteria (prokaryote)
- protective slimy layer
- retains moisture
- allows organism to adhere to other surfaces
plasmid in bacteria (prokaryote)
- circular piece of DNA
flagellum in bacteria (prokaryote)
- tail like structure
- rotates to move cell
pili in bacteria (prokaryote)
- hair like structure
- attract other bacterial cells / adhere
mesosomes in bacteria (prokaryote)
- infoldings of inner membrane
- contains enzymes for respiration
- increase SA
what is a virus?
non-living microorganism
consists of nucleic acid enclosed in a protective protein husk (capsid)
lipid layer forms an envelope
- acellular
what do viruses do?
invade cells
take over cells metabolism
use host cells machinery to replicate
structure of a virus
- core of nucleic acid (DNA/RNA)
- surrounded by a protein coat, CAPSID (coded by viral genes)
what is the cell theory
- new cells are formed from other existing cells
- cells are the fundamental unit for life (structure, function, organisation of living organisms)
- cells contain genetic material transferred to daughter cells
levels of organisation
- groups of cells with a shared specific function are arranged into tissues
- several types of tissues combine to from an organ
- multiple organs come together to form an organ systems
- organ systems make up an organism
differentiation definition
development of a cell into a specific type
becoming specialised in structure and reactions
tissue definition
group of cells working together with a common function, structure and origin
organ definition
several tissues in a structural unit
work together to form a specific function
organ system definition
group of organs
work together with a particular role
organism definition
all bodily systems working together
forming a discrete individual
what is epithelial tissue?
- continuous layer lining internal and external surfaces
- no blood vessels
- some have nerve endings
- sit on a basement membrane
- protective or sensory function
types of epithelial tissues
- simple cuboidal
- columnar
- squamous
what is simple cuboidal epithelial tissue?
- cube shaped
- 1 cell thick
- in PCT and salivary glands
- can be ciliated
what is columnar epithelial tissue?
- elongated cells
- line tubes (e.g. trachea,oviduct) allowing substances through
- may have cilia
what is squamous epithelial tissue?
- flattened cells on basement membrane
- form walls of alveoli
- line Bowman’s capsule
what are ciliated epithelial?
- contain goblet cells
- secrete mucus
- move harmful particles out the body
types of muscle tissue
- skeletal (striated)
- smooth
- cardiac
what is skeletal muscle tissue?
- generates movement
- bands of long fibres
- produce powerful, voluntary contractions
- tire easily
- striped / striated
what is smooth muscle tissue?
- individual spindle shaped cells
- contract rhythmically
- in skin
- in blood vessel walls
- involuntary contractions
- weaker
what is cardiac muscle tissue?
- only in the heart
- striped cells but lack long fibres (of skeletal)
- contract rhythmically without nerve/hormone stimulation
- contractions can be modified
- don’t tire
what is connective tissue?
- connects, supports or separates tissues and organs
- elastic and collagen fibres
- e.g. bones, tendon, blood cell
adaptions of epithelial cells
- microvilli; increase SA for absorption of nutrients
- thin; decreases diffusion distance for gas exchange
- ciliated; moves mucus out of breathing system
capsule vs capsid
- capsid: outer protective layer of a virus
- capsule: outer protective layer of bacteria
structure of human cell vs virus (3)
- humans genetic material is DNA, virus only has RNA
- human cell has cell membrane, virus has capsid
- human cell has nucleus, virus doesn’t
- human cell has membrane bound organelles, virus has no organelles
- human cell has chromosomes, viruses don’t
how is viral RNA replicated? (3)
- RNA released from virus capsid inside host cell
- RNA polymerase reads base sequence on virus RNA
- free RNA nucleotides pair with nucleotides on virus RNA
- complementary base pairing
- RNA polymerase catalyses formation of RNA molecule
how is viral RNA used to make viral protein molecules? (3)
- replicated viral RNA attaches to ribosome
- tRNA matches anticodon to codons on viral RNA
- complementary base paring
- tRNA brings amino acids to ribosome
- amino acids joining by peptide bonds = polypeptide
why is a virus not considered to be a cell?
it is acellular
it has no membrane bound organelles
