Cell Structure & Organization Flashcards
Plant cell exclusive characteristics:
- vacuole (stores food+water, helps maintain shape of cell)
- cell wall (rigid wall to maintain shape of cell)
- chloroplasts (contains chlorophyll to absorb light energy
Specialised cells:
- red blood cell
- muscle cell
- ciliated cell
- root hair cell
- xylem vessel
- palisade cell
Red blood cell:
Function:
- O2/CO2 transport
Adaptation:
- bi-concave shape (large surface area)
- anucleate (no nucleus; to accommodate more O2/CO2)
- flexible (to fit through blood vessel lumen)
- contains haemoglobin (to bind O2/CO2)
Muscle cell:
Function:
- contracts to get structures closer together
Adaptation:
- long
- contains lots of mitochondria (more energy!!)
- lots of protein fibers for contraction
Ciliated cell:
Function:
- move mucus up the trachea
Adaptation:
- has cilia (to sweep mucus upwards)
Root hair cell:
Function:
- absorb minerals and water
Adaptation:
- elongated shape (large surface area)
- lots of mitochondria (supplies energy for active transport)
- concentrated vacuole (helps absorb water via osmosis)
Xylem vessel:
Function:
- transport water
- support plant
Adaptation:
- no cytoplasm (so water passes freely)
- no cross walls (cells connect to form hollow tube)
- lignin (strong + waterproof)
Function of cell membrane:
To control movement of substances in and out of the cell
Function of cell wall:
To withstand the inner pressure of the cell
Define organelle
A specialised part of a cell (e.g. nucleus, chloroplast, mitochondria)
Define cell
Smallest part of a living biological organism that can operate independently as a unit (e.g. RBC)
Define tissue
A group of cells with similar structures and common functions (e.g. muscles)
Define organ
A structure made up of a group of tissues to perform specific functions (e.g. heart)
Define organ system
A group of organs with related functions, working together to perform various body functions (e.g. respiratory system)
Define organism
An individual made up of organ systems that work to keep that individual alive
Phloem vessel:
Function:
- transport of materials in translocation processes
Structure:
- long, continuous strands called vascular bundles
- unlike xylem, it is living
- is made up of: sieve elements; companion cells; and supportive cells
What are sieve elements?
- group of cells in phloem
- responsible for moving sugary fluids
- no nucleus and few organelles when mature (prior to maturing, sieve tube cells do contain vacuoles and other organelles, though)
- rely on companion cells for energy
- have sieve areas: clusters of pores reinforced by platelets of callose (a polysaccharide)
What are sieve cells?
Out of the 2 main conducting cells in the phloem, the sieve cell is more primitive, and is generally found in seedless vascular plants.
Define vascular plant:
A plant with a specialised transportation system (the phloem).
What are sieve-tube cells?
- more advanced type of conducting cell
- elongated individual cells arranged end-to-end
- conducts food materials throughout the plant
- sieve areas in these cells are called sieve plates
What are companion cells?
- specialised parenchyma cells
- carries out basic cellular functions of sieve elements
- has more ribosomes and mitochondria than normal cells, so is more metabolically active than normal cells
- the cytoplasm of a companion cell is connected to sieve-tube elements via plasmodesmata
Define plasmodesmata
A narrow thread of cytoplasm passing through the cell walls of adjacent plant cells
What are parenchyma?
The most abundant cell type in plants, and are usually unspecialised. Characteristics:
- thin cell wall
- large vacuole for storage
- spherical
- regular shape
- elastic
- lots of intracellular space
Functions include photosynthesis, storage, and secretion.
What are collenchyma?
They can be found just below the epidermis in petiole, leaves, and stems, and are usually specialised. Characteristics:
- irregularly thickened walls (with cellulose)
- prism shape
- plastic deformation (is elastic, but remains deformed when structure is altered)
Functions include support and transport of nutrients.
What are sclerenchyma?
Can be found in mature parts of a plant, especially in woody or herbaceous plants. They are generally specialised.
Characteristics:
- die upon maturing
- very thick, lignified cell wall
- impermeable
- in transport-specialised sclerenchyma, the cell wall will contain holes called pits
Functions include support, protection, and transport of water/nutrients.
Common organelles:
- cell membrane
- mitochondria
- nucleus
- cytoplasm
Function of cell membrane
- forms a barrier
- controls movement of substances in and out of the cell
- keeps contents of cell inside
Function of nucleus
- controls activities in the cell
- contains genetic information
- controls how cells develop/divide/reproduce/grow
