b1 Flashcards
difference between prokryotic and eukaryotic cells
prokaryotic - bacterial cells. much smaller. cytoplasm and cell membrane surrounded by cell wall. the genetic material is not enclosed in nucleus. a single DNA loop, one or more small rings of DNA - plasmids
eukaryotic - animal and plant cells. genetic material enclosed in a nucleus
cell membrane
holds cell together, seperates the inside of the cell from outside and controls what enters and leaves the cell
cytoplasm
jelly-like substance where chemical reactions happen, surrounds sub-cellular structures, anaerobic respiration
DNA
genetic material that controls activities of cells
ribosomes
site of protein synthesis in cell
mitochondria
where aerobic respiration happens (energy is released to fuel cellular activities)
chloroplasts
green pigment called chlorophyll which absorbs light energy and has enzymes which are needed for photosynthesis
cell wall
made of cellulose which gives cells extra support, defining it’s shape
permenant vacuole
contains cell sap - solution of sugars and salts dissolved in water
helps support the shape of the cell
used for storage of certain materials
how are nerve cells specialised
have elongated structures which allows them to coordinate info from cns with rest of body
- the axon is covered with a fatty sheath which speeds up nerve impulses
how are muscle cells specialised
have lots of mitochondria to provide sufficient energy by aerobic respiration for muscle contraction
they also contain layers of fibres which allow them to contract
how are sperm cells specialised
middle of cell has lots of mitochondria for energy by aerobic respiration for tail to move forwards quickly
how are root hair cells specialised
they absorb mineral ions and water from soil
small hairs which increase surface harea so rate of osmosis is quicker
thinner walls so shorter diffusion distance
mitochondria for energy for active transport for mineral ions
permenant vacuole more concentrated so good gradient for faster rate
how are xylem cells specialised
transport tissue for water and dissolved ions
cells are dead (no cytoplasm or organelles) to allow free passage of water
outer walls thickened with lignin, strengthening the tubes, which helps support the plant
how are phloem cells specialised
transport of dissolved sugars and amino acids
made of living cells which are joined end to end.
they have holes called sieve plates which form tubes allowing sugars and amino acids to flow
why is cell differentiation important?
so that it can get a structure and composition of subcellular structures which enables it to carry out a certain function
differentiation in plants vs animals
plants retain ability to differentiate throughout life but most animals differentiate at an early stage
how has electron microscopy increased understanding of sub-cellular structures?
has a much higher magnification and resolving power than light microscope. this means it can be used to study cells in finer details. this has enabled biologists to see and understand more sub-cellular structures
light vs electron microscope - how they work
electron - ises beams of electrons. the wavelength of electron beam is much smaller than visible light so they have higher magnification and resolution
light - uses light and lenses to form magnified mage of a specimen
magnification
size of image / size of real object
how to prepare a microscope slide
- they are prepared on slide to be observed under a light microscope
use tweezers to get a layer of cells. add a drop of water to a clean slide. place tissue into water on slide. add iodine stain so that structures within the cell can be observed. then place a cover slip on top of the specimen
what is diffusion
spreading out of particles of any substances in solution, or particles in gas, resulting in net movement from an area of high concentration to area of lower concentration.
factors affecting rate of diffusion and why
concentration difference - larger concentration difference means faster rate of diffusion
surface area - larger the surfacte area, the faster rate of diffusion as more particles pass through
temperature - higher temperature means faster diffusion because particles have more energy so move around faster
define osmosis
movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of lower water concentration
how is the small intestine adapted to its role
it absorbs digested food molecules into the bloodstream through its walls
- has highly folded surface - many vilus, which increases the surface area
- has only one layer of epithelial cells which decreases diffusion distance
- each villus has a good blood supply which maintains a concentration gradient
how are lungs adapted for its function
adapted for gas exchange between air in alveoli and the blood so cells have oxygen for aerobic respiration and to remove carbon dioxide
- it has millions of alveoli and the shape of the alveoli is spherical which means larger surface area
- wall of each alveoulus is one cell thick and a good blood supply which decreases diffusion distance and maintains a concentration gradient
how are gills adapted to its role?
gas exchange between water flowing through gills and blood to supply cells with oxygen for aerobic respiration and remove carbon dioxide
- each gill has smaller plates called filaments which are covered in projections called lamellae which increases surface area
- dense capillary network which ensures a good blood supply, and flows in opposite direction to water passing through gills maintaining a concentration gradient
how roots in plants are adapted for exchanging minerals
- root network is branched and surface of roots have root hair cells which have specialised structure with root hairs which increases surface area
how are leaves in plant adapted to its role?
- have stomata which are tiny openings and cover the lower side of leaf which decreases diffusion distance for carbon dioxide and oxygen
- lower layer of the leaf is made from spongy mesophyll cells which allow air to circulate inside the leaf
define active transport
movement of substances from an area of low concentration to an area of higher concentration using energy from respiration
active transport in plants
so that mineral ions can be absorbed from the soil into root hairs as the soil has dilute concentrations. this is required by plants because they need mineral ions for healthy growth
active transport in animals
sugar molecules in low concentrations to be absorbed into the blood from the gut. sugar molecules are used for cell respiration
microscope practical - onion cells
Use tweezers to peel back a layer of epidermal tissue
Add a drop of water to a clean slide
Spread the epidermal tissue out on the slide
Ensure the tissue is one cell thick
Add a drop of dye / iodine / stain so structures are visible / clear
Place a cover slip over the top
Tap gently to remove air bubbles
Dab away any excess dye from the slide
