cell structure + organisation Flashcards
protoplasm
- mass of living components/matter
- made up of cell surface membrane, nucleus, cytoplasm
- comprises of other cell organelles (structures found in the cytoplasm, able to carry out cell activities)
e.g. cell wall is not protoplasm as it is a dead structure
define organelle
- a specialised subunit that has a specific function in the cell
- all organelles have their own membrane(s)
L.S. and T.S.
- L.S. cut along the length of the cell
- T.S. cut at the right angle to the length of the cell
- different planes of cut, different views
optional what processes must a living organism be able to do?
- feed + release energy to survive
- reproduce
- maintain certain conditions (e.g. temperature)
cell surface membrane
- surrounds the cytoplasm
- made up of lipids and proteins
- it is partially permeable, allowing only small and soluble substances to pass through
- controls the movement of substances in and out of the cell
cell wall (only in some plant cells)
- surrounding the cell membrane; encloses the entire plant cell
- made of cellulose
- it is fully permeable and allows all particles to pass through it
- protects the cell from injury and gives the cell a fixed shape
- prevents the cell from bursting
cytoplasm
- jelly-like substance that fills the inside of the cell (found between the cell membrane and the nucleus)
- site of cellular activities
- contain/suspends specialised structures called organelles
chloroplast
- contains a green pigment called chlorophyll
- oval structures found in some plant cells
- essential for photosynthesis (process by which plants make food)
nucleus (organelle)
- controls cell activities (e.g. cell growth, repair of worn-out parts)
- essential for cell division (e.g. red blood cell without a nucleus is unable to divide)
- contains genetic information (chromosomes)
- surrounded by a nuclear membrane (separates the contents of the nucleus from the rest of the cytoplasm)
- double membrane-bound organelle
chromosomes + chromatin (found in the nucleus)
chromatin
- network of thread-like structures
- made up of DNA (deoxyribonucleic acid) which carries hereditary information
- chromatin threads condense into chromosomes during cell division
chromosomes
- long thread-like structure found within the nucleus
- made up of (proteins +) DNA (deoxyribonucleic acid) which carries hereditary information (+ carries instructions that a cell needs for carrying out its activities)
- condense + shorten into thick, rod-shaped structures during cell division
rough endoplasmic reticulum
- network of flattened spaces lined with a membrane
- outer surface of RER is continuous with the nuclear membrane/envelope
- RER appears rough because its surface is studded with ribosomes
- transports proteins made by the ribosomes to the Golgi apparatus (GA)
smooth endoplasmic reticulum
- SER is more tubular than RER
- SER is connected to RER
- does not have ribosomes attached to its surface
- synthesises subtances such as fats and steroids
- involved in detoxification (converts harmful substances into harmless substances)
vesicles
- formed from ER and Golgi body
- small, (usually) temporary organelle
- formed by a membrane and filled with a liquid
- moves substances into/out of the cell
Golgi apparatus/body
- consists of a stack of flattened spaces surrounded by membranes (+ shaped like a disc)
- chemically modifies substances made by the ER
- stores and packages the substances in vesicles for secretion out of the cells
essay: how are substances made by the ER transported out of the cell?
1) vesicles containing substances made by the ER pinch off from the ER
2) vesicles fuse with the GA releasing substances made by the ER which may be modified by the GA
3) secretory vesicles containing modified substances pinch off from the GA and move towards the cell membrane
4) secretory vesicles fuse with the cell membrane and their contents exit the cell
mitochondrion/mitochondria
- small oval/sausage-shaped organelles
- site of aerobic respiration
- food substances are oxidised/broken down to release energy for cellular activities (used by the cell for for cell growth, reproduction etc)
- double-membrane bound organelle
vacuole
fluid filled space enclosed by a PPM
- stores substances within a cell (water, mineral salts, sugar, amino acids, waste materials) - known as cell sap in a plant cell
- plays a key role in keeping plant cells turgid
- animal cell vacuoles usually exist temporarily
plant cell VS animal cell
cell wall
PC: present
AC: absent
vacuole:
PC: one/few; large; central
AC: numerous; small; scattered
chloroplasts
PC: present in photosynthetic cells
AC: absent
what is differentiation/ how is it carried out?
- some cells develop/lose certain structures to enable them to carry out specific functions
- cell adaptations enhance their functionality, enabling the organism to survive and thrive in its environment
the process by which a cell becomes specialised for a specific function
red blood cell
adaptations:
1) contains haemoglobin
2) circular biconcave shape
3) absence of nucleus
4) flexible
functions:
1) binds to oxygen reversibly and transports (where to where) it around the body
2) increases surface area-to-volume ratio for increased rate of oxygen uptake and release
3) allows packing of more haemoglobin for transport of oxygen
4) easily squeezes through capillaries
muscle cell
adaptations:
1) contain many mitochondria
2) has contractile protein fibers
3) has many nuclei
functions:
1) provide energy for contraction of muscle cells
2) contract and relax to bring about movement of body parts
3) allow for cell division to replace dead muscle cells
root hair cell
adaptations:
1) long narrow extension
2) maintains a lower water potential in vacuole
functions:
1) increase surface area-to-volume ratio for increased rate of absorbtion of water and mineral salts
2) allow water to enter the root hair cell via osmosis
application
- stem cells can develop into specialised cells
- scientists can grow cells of different organs in the laboratory and transplant them into humans
- potential to treat diseases that were once untreatable (e.g. lukemia)
ribosomes
- small round structures
either: - attached to the membrane of the RER;
synthesises proteins usually transported out of the cell - lie freely in the cytoplasm;
synthesises proteins usually used within the cytoplasm of that cell
