Cells, tissues, organs and body systems Flashcards
(33 cards)
define uni-cellular
single celled, the single cell is able to perform all life functions
multicellular organisms have what 4/5 levels of organisations - ranging from simplest to most complex
- cells
- tissues
- organs
- organ systems
describe cells
basic unit of structure in living things
may serve a specific function with the organism
e.g. blood cells, nerve cells
describe tissues
made up of cells that are similar in structure and function and work together to perform a specific activity
e.g. blood, bone
describe organs
made up of tissues that works together to perform a specific activity
e.g. heart, brain, skin
describe organ systems
group of two of more tissues that work together to perform a specific function
e.g. circulatory system, nervous system
how many organ systems are in the human body>
11
circulatory digestive edocrine excretory immune integumentary muscular nervous reproductive respiratory skeletal
autotrophs
able to make their own energy-containing organic molecules from inorganic raw material by using energy sources such as light
e.g. plants
heterotrophs
must use food that comes from other organisms in the form of fats, carbohydrates and proteins
what are the two main stages within photosynthesis
Light dependent reactions:
- occur in the grana, and require the direct energy of light to make energy-carrier molecules that are used in the second process
Light independent reactions:
- occur in the stroma of the chloroplasts
name 5 things in the structure of a leaf
- upper epidermis
- palisade mesophyll
- spongy mesophyll
- vascular tissue
- leaf shape
describe the upper epidermis and its role
consists of a single layer of cells found on the upper surface of the leaf
covered by a thick waxy cuticle
main function is water conservation. It prevents the loss of water from the upper surface where the light intensity and heat are the greatest.
describe the palisade mesophyll and its role
consists of tightly packed cylindrical cells.
contains many chloroplasts as it is the main photosynthetic tissue.
found on the upper half of the leaf (upper surface) where the light intensity is the greatest.
describe the spongy mesophyll and its role
made up of loosely packed cells.
found in the lower half of the leaf (lower surface)
has few chloroplasts
provides gas exchange (CO2 uptake and O2release) and therefore needs to be close to the stomata found in the lower epidermis
describe the vascular tissue and its role
Consists of xylem and phloem which are found in the veins of the leaf.
The veins in the leaf are positioned in the middle so that all the cells are in close contact with the vascular tissue.
The xylem consists of xylem vessels (dead structure) which are long and tubular and transports water into the leaf to replace the water that has been lost through transpiration.
The phloem is made up of living cells with pores in between them. It transports the products of photosynthesis out of the leaf.
describe the leaf shape and its role
The orientation of a surface, such as a leaf, influences the energy balance of the surface.
The heat load of a leaf can be influenced by air movement and by evaporation (transpiration) of water from a leaf. This means the larger the leaf the more surface area available for light energy. This is beneficial for photosynthesis but needs to be balanced with water loss from transpiration.
where does photosynthesis occur in plants
in the leaves
what are the 2 main vascular tissues in plants
xylem
phloem
explain role of the xylem and how it’s adapted
transports water and minerals
one way only (upwards)
no end walls between cells
thick walls stiffened with lignin
how does transpiration enable upward water movement in a plant
- evaporation of water from leaf surfaces
- water is cohesive (cohesive forces between water molecules pulls them up to replace the evaporated water)
explain role of the phloem and who it’s adapted
transports sugar molecules
cells have end walls with perforations
two-way flow (up and down)
materials able to move in the phloem as a result of active transport, osmosis and turgor pressure
where are sugars produced in a plant
in the leaves
describe what occurs in the phloem
- sugars produced in leaves (sinks) as part of photosynthesis
- these sugars are moves across to the phloem cells called sieve tub elements (via active transport)
- because of high solute concentration water moves into these cells via osmosis
- the inflow of water increases turgor pressure at the source, causing the movement of water and carbohydrates through the seven tube elements toward a sugar sink
what is sap
a mixture of water and minerals that flow through the xylem
