3.2.1 cell structure and 3.2.3 Flashcards
define the term of eukaryotic cells
DNA is contained in a nucleus , contains membrane-bound specialised organelles
define the term of prokaryotic cells
single celled organism without a nucleus or membrane bound organelles
state the relationship between a system and specialised cells
specialised cells = tissues that perform specific function = organs made of several tissue types = organ systems
cell membrane function
- mainly made of lipids/proteins
- regulates movement of substances in and out of the cell by being selectively permeable
- has receptor molecules = allows it to respond to chemicals e.g. hormones
- involved in cell signalling/ recognition
structure of the nucleus
- surrounded by nuclear envelope (semi permeable double membrane)
- nuclear pores in the nuclear envelope
- dense nucleolus
function of the nucleus
- controls cells activities (by controlling the transcription of DNA)
- DNA contains instructions to make proteins
- pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm
- nucleolus makes ribosomes
description of mitochondrion
- oval shaped
- double membrane
- inner membrane is folded to form cristae
- inside is the matrix = contains enzymes involved in respiration
function of mitochondrion
-site of aerobic respiration which produces ATP (common energy source in the cell)
chloroplast description
- double membrane
- has thylakoid membranes inside (when stacked up form grana)
- grana linked together by lamellae ( thin/flat pieces of thylakoid membrane)
chloroplast function
- where photosynthesis takes place
- some parts of photosynthesis happen in the grana and some in the stroma (thick fluid found in chloroplasts)
golgi apparatus description
- group of fluid filled membrane bound flattened sacs
- vesicles often seen at the edges of the sacs
golgi apparatus function
- processes and packages new lipids/proteins
- makes lysosomes
golgi vesicle structure
- small fluid filled sac in cytoplasm surrounded by a membrane and produced by the golgi apparatus
golgi vesicle function
- stores lipids/proteins made by the golgi apparatus and transports them out of the cell via the cell surface membrane
lysosome description
- round organelle surrounded by a membrane
- no clear internal structure
lysosome function
- contains hydrolytic enzymes
- kept separate from cytoplasm by surrounding membrane and used to digest invading cells/ break down worn out components of the cell
ribosome description
- very small organelle that floats free in cytoplasm or attached to RER
- made up of proteins and RNA
- not surrounded by a membrane
ribosome function
- where proteins are made
rough endoplasmic reticulum description
- system of membranes enclosing a fluid filled space
- surface covered with ribosomes
rough endoplasmic reticulum function
folds/processes proteins that have been made at the ribosomes
smooth endoplasmic reticulum description
- similar to RER but with no ribosomes
smooth endoplasmic reticulum function
synthesis and processes lipids
cell wall description
- rigid structure surrounding the cell
- plants/algae= made of cellulose
- fungi = made of chitin
- bacteria = made of murein
cell wall function
- supports cell
- prevents them changing shape
cell vacuole description
- membrane bound organelle found in cytoplasm
- contains cell sap (weak solution of sugars/salts)
- surrounding membrane is called the tonoplast
cell vacuole function
- helps maintain pressure inside cell/ keep cell rigid
- involved in isolation of unwanted chemicals inside the cell
common cell adaptations
- folded membrane/ microvilli increase surface area e.g. for diffusion
- many mitochondria = lots of ATP for active transport
- walls one cell thick = reduces distance of diffusion pathway
prokaryotes - capsule
- made up of secreted slime
- helps protect bacteria from attack by cells of the immune system
prokaryotes - plasmids
- small loops of DNA, aren’t part of the main circular DNA molecule
- contain genes e.g. for antibiotic resistance and can be passed between prokaryotes
prokaryotes - DNA
- floats free in the cytoplasm
- circular DNA, present as one long coiled up strand
- not attached to any histone proteins
prokaryotes - flagellum
- long hair like structure, rotates to give movement
compare eukaryotes and prokaryotes
both have:
- cytoplasm
- cell surface membrane
- ribosomes
contrast eukaryotes and prokaryotes (eukaryotes)
- larger cells/often multicellular
- always have organelles/nucleus
- linear chromosomes associated with histones
- larger ribosomes (80s)
- mitosis/ meiosis = asexual/sexual
- always cytoskeleton
contrast eukaryotes and prokaryotes (prokaryotes)
- small cells/unicellular
- no membrane bound organelles/nucleus
- circular DNA not associated with proteins
- smaller ribosomes (70S)
- binary fission (always asexual reproduction)
- sometimes cytoskeleton
are viruses cells?
no: they are acellular and non-living, no cytoplasm, can’t self-reproduce, no metabolism
structure of a viral particle
- linear genetic material (DNA/RNA) and viral enzymes
- surrounded by capsid (protein coat) with attachment proteins sticking out of it
structure of an enveloped virus
- simple virus surrounded by matrix proteins
- matrix protein surrounded by envelope derived from cell membrane of host cell
- attachment proteins on surface
role of capsid
- protects nucleic acid from degradation by restriction endonucleases
- surface sites enable viral particle to bind to and enter host cells or inject their genetic material
role of attachment proteins
enable viral particle to bind to complementary sites on host cell : entry via endosymbiosis
describe how optical microscopes work
- lenses focus rays of light and magnify the view of a thin slice of specimen
- different structures absorb different amounts and wavelengths of light
- reflected light is transmitted to the observer via the objective lens and eyepiece