characteristics of living organisms

eukaryotic organisms

Eukaryotic organisms can be multicellular or single-celled and are made up of cells that contain a nucleus with a distinct membrane

plants

contain chloroplasts to carry out photosynthesis

have cellulose cell walls

store carbohydrates as starch or sucrose

animals

don't contain chloroplasts

don't have cell walls

can't photosynthesis

store carbohydrates as glycogen

have a nervous system

can move from place to place

fungi

don't photosynthesise

cell walls made of chitin

some are single celled

some have a body or mycelium

mycellium made up of tiny threads
called hyphae

feed by extra cellular digestion secreted outside onto the food and molecules digested are absorbed into the hyphae

satrotrophic nutrition

carbohydrates stored as glycogen

some are paracitic

feed on living mater

protoctists

examples

amoeba

causes dysentry

contains animal features

plasmodium

causes malaria

chlorella

plant like features

algae

microscopic and single celled

some group together to form
layers of chains

usually aquatic

prokaryotic organism

Bacteria

singlecelled but different shapes -
rods or spherical

no nucleus

circular chromosome of DNA

most photosynthesise

parasitic or
saprobionts/decomposers

Prokaryotic organisms are always single-celled and do not contain a nucleus (instead, the nuclear material of prokaryotic cells is found in the cytoplasm)

pathogens

any microorganism that causes disease in another organism

pathogens include

bacteria

fungi

protoctists

viruses

can cause meningitis or tubercolosis

can cause athletes foot or cattle ringworm

plasmodium causes Malaria

not living

take over cells metabolic pathways

HIV causes AIDs and the Influenza virus causes the flu

cell structures

nucleus

contains genetic material in chromosomes which control how cells work

controls cell division

cytoplasm

supports cell structures

site of many metabolic reactions

contains water and many solutes

cell membrane

holds the cell together

controls the substances entering and leaving the cell

cell wall

supports the cell and defines its shape

chloroplasts

site of photosynthesis

the chlorophyll absorbs light energy needed for the reaction to occur

vacuole

contains cell sap

used for storage of certain material

also helps support the shape of the cell

mitochondria

site of aerobic respiration

ribosomes

site of protein production in protein synthesis

plant vs animal cells

plants have a cell wall made of cellulose, a permanent vacuole filled with cell sap and many plant cells also contain chloroplasts. none of these are found in animal cells

stem cells

characteristics

a stem cell is an undifferentiated cell which can undergo division to produce many more similar cells

some of these will differentiate to have different functions

they are important in growth, development and repair

embryonic stem cells

form when an egg and sperm cell fuse to form a zygote

they can differentiate into any type of cell in the body

scientists can clone these cells and direct them to differentiate into almost any cell in the body

these could potentially be used to replace insulin-producing cells in those suffering from diabetes for examples

adult stem cells

if found in bone marrow, they can form many types of cells including blood cells

meristems in plants

found in root and shoot tips

they can differentiate into any type of plant, and have this ability throughout the life of the plant

they can be used to make clones of the plant

stem cells in medicine

benefits

risks

can be used to replace damaged cells, such as in type 1 diabetes, multiple sclerosis and paralysis caused by spinal cord injuries

bone marrow transplants for adult stem cells can be used to treat blood cell cancers, such as lukaemia

can grow whole organs for transplants

no rejection as it is made from the patients own cells

can allow for the testing of millions of potential drugs without animal testing

ethical issues of destroying unused embryos

no guarantee in how successful these therapies will be and if there will be any long term effects

mutations could occur in cultured stem cells

difficult to find suitable stem cell donors

levels of organisation

organeele, cell, tissue, organ, organ syst3em

specialised cells

examples of specialised cells

phloem cells

despite losing many sub-cellular structures, the energy these cells need to be alive is supplied by the mitochondria of the companion cells

cell walls of each cell form structures called sieve plates when they break down, allowing the movement of substances from cell to cell

specialised to carry the products of photosynthesis to all parts of the plants

xylem cells

lignin causes the cells to die, becoming hollow and they are joined end to end to form a continuous tube so water and mineral ions can move through

specialised to transport water and mineral ions up the plant

root hair cells

mitochondria to provide energy for the active transport of mineral ions into the root hair cell

the large permanent vacuole affects the speed of movement of water from the soil to the cell

have a large surface area due to root hairs

specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots

muscle cells

he problems arising from the disposal of radioactive waste and how the
associated risks can be reduced

lots of mitochondria to provide energy from respiration for contraction

special proteins slide over each other, causing the muscle to contract

specialised to contract quickly to move bones

nerve cells

he problems arising from the disposal of radioactive waste and how the associated risks can be reduced

having lots of extensions from the cell body (dendrites) means branched connections can form with other nerve cells

the axon is long, enabling the impulses to be carried along long distances

specialised to transmit electrical signals quickly from one place in the body to another

sperm cells

the tip of the head has digestive enzymes which break down the outer layers of membranes of the egg cell

many mitochondria to supply the energy to allow the cell to move

streamlined head and long tail to aid swimming

specialised to carry the male's DNA to the egg cell for successful reproduction

cells can either differentiate once early on or have the ability to differentiate their whole life (stem cells)

cells specialise by undergoing differentiation

those which have developed certain characteristics in order to perform particular functions