topic 1 - cell biology

prokaryote

single celled organism with no nucleus

prokaryote example

bacteria cell

eukaryote

organisms whose cells have DNA enclosed in the nucleus

organelles

structure within a cell

cell membrane

controls the movement of substances in and out of the cell (semi-permeable)

cell wall

made of cellulose, provides strength and support, not found in animal cells

ribosomes

where proteins are made (protein synthesis)

plasmid

small rings of DNA found in bacteria

cellulose

makes up plant and algae cell walls to give them strength, formed from glucose

cell specialisation

a cell that differentiates to perform a specific function

axon

long projection of the nerve cell that carries the impulse from one place to another

dendrites

found at one end of the nerve cell, makes connections with other nerve cells

acrosome

found in the head of the sperm, contains enzymes to break down the egg membrane

root hair cells

plants specialised to take up water and mineral ions from the roots

palisade cell

plant cells containing lots of chloroplasts for photosynthesis

lignin

forms spirals for support in the walls of xylem cells

xylem

cells that transport water and minerals from roots to leaves

phloem

cells that transport sugars from the leaves into other parts of the plant

sieve plates

allows dissolved foods to move freely up and down phloem cells

companion cells

keeps the phloem cells alive

mitosis

cell division need for growth and repair

chromosome

strands of DNA containing several genes located in the nucleus, human body cells have 23 pairs

gene

section of DNA that codes for a protein

stem cell

unspecialised cell that can form many types of cells

meristem

stem cells found in plants found in the tips of roots and shoots

therapeutic cloning

an embryo produced with the same genes as the patient so the stem cells are not rejected

isotonic

when the surrounding solution has the same concentration as inside the cell

hypertonic

when the surrounding solution has a lower concentration than inside the cell

hypotonic

when the surrounding solution has a higher concentration of water than inside the cell

turgid

cells that have swelled due to the uptake of water by osmosis

plasmolysis

when the vacuole and cytoplasm shrink due to loss of water by osmosis

alveoli

tiny air sacs in the lungs where gas exchange takes place

stomata

pores on the underside of leaves, where gas exchange takes place for plants

how are sperm cells specialised

for reproduction, long tail and streamlined head to help it swim, mitochondria for energy, carries enzymes in head to digest through the egg cell membrane

how are nerve cells specialised

rapid signalling, long and have branched connections to connect to other nerve cells and form a network throughout the body

how are muscle cells specialised

for contraction, long and have lots of mitochondria to generate energy needed for contraction

how are root hair cells specialised

absorbing water and minerals, long hairs to stick out from the soil which gives them a large surface area for absorbing water and mineral ions from the soil

how are phloem and xylem cells specialised

transporting substances, cells are long and joined from end to end, xylem cells are hollow and phloem cells have very few subcellular structures so stuff can flow

when is active transport used

when there is a lower concentration of nutrients in the gut but a higher concentration of nutrients in the blood

how are alveoli specialised to maximise diffusion

enormous surface area, moist lining, thin walls, good blood supply

what do villi do

increase surface area so digested food is absorbed much more quickly into the blood

qualities of villi

single layer of surface cells, very good blood supply to assist quick absorption

how do leaves let gases diffuse in and out of cells

the water vapour evaporates from the cells inside the leaf then escapes by diffusion because theres a lot of it inside the leaf and less in the air outside

what are eukaryotic cells found in

plants, fungi, animals and protists