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what is diffusion?
the net movement of molecules from a higher concentration to a lower concentration until it reaches equilibrium without the use of energy (passive)
what does the rate of diffusion depend on?
wind
distance
temperature
pressure
how is diffusion related to breathing?
oxygen is inhaled and diffuses through the lungs and into the bloodstream, the oxygen is then transported throughout the body
carbon dioxide is the waste gas produced from respiration. carbon dioxide diffuses from body tissues into the blood stream & gets exhaled out the lungs
what are adaptations that makes gas exchange in the alveoli more efficient?
one cell thick
large combined surface area
covered by a network of fine capillaries, lets gases pass almost directly between the lungs and bloodstream
moist, encourages gas molecules to easily dissolve
how is digestion related to diffusion?
carbs, proteins & fats are made up of large molecules that cant be readily absorbed by the body. digestion breaks down these large food molecules into smaller ones (glucose, amino acids & fatty acids). small food molecules are then absorbed in the small intestine, diffusing across the intestinal wall & the bloodstream
how is the small intestine related to diffusion?
the walls of the small intestine are lined with very small finger like projections (villi). they increase the surface area of the small intestine. they also have adaptations such as being one cell thick, which allows it to increase its rate of diffusion
how is the placenta related to diffusion?
the placenta is an organ that develops in the uterus of female mammals during pregnancy. the umbilical cord connects the placenta to the fetus. the placenta enables nutrients and oxygen to pass from the mother to the fetus by diffusion, and waste substances to diffuse from the fetus back to the mother. the placenta is also able to filter out certain molecules and bacteria, but unable to filter out/stop many harmful substances such as alcohol, chemicals and some viruses from reaching the fetus.
how are nerve impulses related to diffusion?
a synapse is a junction between 2 neurons across which electrical signals must pass. neurotransmitter molecules diffuse from vesicles towards the neurotransmitter receptors, moving from an area of high concentration to low concentration
what is osmosis?
the diffusion of water molecules from a high water potential to low water potential solution across a selectively permeable membrane.
what does osmosis have to do w cells?
plant and animal cells are surrounded by partially permeable plasma membranes. plant cells additionally have strong cell walls surrounding the membrane, offering support & protection.
animal cells don’t have a cell wall. in dilute sol, osmosis can cause animal cells to swell up & burst (lysis).
in concentrated sol, osmosis causes animal cells to crenate. the water loss causes the cells to shrink.
what does the hypothalamus do?
controls the kidney, which controls the concentration of water & salt in the blood
what is active transport?
the movement of substances/molecules by diffusion across a cell membrane, against the concentration gradient, until the concentration on both sides of the cell membrane reaches equilibrium, using energy from respiration.
active transport in plants
plants need to absorb mineral elements from the soil for healthy growth. when the concentration of minerals in the soil is lower than the ones inside the plant, active transport is used to absorb the minerals against the concentration gradient.
active transport in humans
during digestion, the villi absorbs soluble nutrients. over time, the concentration of the nutrients in the villi reaches equilibrium with the concentration in the gut.
what is turgid?
the swelling of plant cells when there is a high uptake of water.
what are the adaptations of red blood cells?
no nucleus, allows more surface area for haemoglobin, enhancing the rate of diffusion of oxygen
combines w oxygen to form oxyhaemoglobin, its an iron rich protein that transports oxygen
a biconcave disc shape, enabling the cell to move rapidly even in narrow capillaries
what are the adaptations of muscle cells?
spindle shape, enabling them to slide over each other easily when the tissue contracts & relax in an antagonistic manner.
what are the adaptations of ciliated cells of the respiratory tract?
mucus: traps dust & bacteria, also serves as a lubricant for the air passages
cilia: sweeps trapped dust & bacteria upwards into the oesophagus
what are the adaptations of root hair cells?
extended cell wall: increases surface area for the absorption of water by osmosis & dissolved mineral salts by active transport
what are the adaptations of the xylem?
hollow center: conducts water & dissolved mineral salts
lignified cell wall: to support and keep the plant upright
what are the animal tissues? (5)
muscle
bone
liver
skin
lung
what are the plant tissues? (3)
mesophyll
xylem
phloem
