cellular structure and function

organelles, SA:V, cells as basic unit of life

cell

smallest unit of life

cytosol

fluid in which organelles are suspended

multicellular

organism made up of more than one cell

unicellular

single cell organism

eukaryote

larger and more complex, have membrane bound organelles and DNA inside a nucleus

prokaryote

simple structures, no membrane bound organelles, no nucleus

eukaryote+ prokaryote similarities

contain genetic material, cytosol, ribosomes, surrounded by membrane

nucleoid

site of DNA in prokaryotes, extra chromosomal DNA are in circular plasmids

nucleus

largest organelle, houses DNA, controls cell activity and cell division

nuclear envelope

double membrane enclosing nucleus, with pores for mRNA to leave

nucleolus

round structure inside nucleus, site of ribosome synthesis, contains proteins and ribosomal RNA

mitochondria

small organelle, has double membrane with highly folded inner membrane for cristae, produces ATP through aerobic respiration

ribosome

has no membrane, manufactures proteins from simple amino acids

rough endoplasmic reticulum

made of channels formed by membranes, attached to outer membrane of nucleus, transports proteins, contains surface ribosomes

smooth endoplasmic reticulum

made of channels formed by membranes, has no surface ribosomes, forms and transports lipids

golgi apparatus/complex

stacked flat membrane sacs, packages and transports large molecules to be secreted from the cell

cytoplasm

semi-fluid material enclosed by plasma membrane, contains everything inside cell except DNA/nucleus

vacuole

usually large organelle surrounded by membrane, contains cell sap and maintains cell turgidity

contractile vacuole

found in microorganisms, expands by filling with water, and then contracts by expelling water

turgid

swollen vacuole, pushing cell membrane to cell wall

tonoplast

vacuole membrane

cytoskeleton

made up of small and thin microfilaments and larger and hollow microtubules, gives cell shape, provides mechanical strength and facilitates organelle movement

centriole

two rod like structures made of right angled microtubules, moves chromosomes apart during cell division (mitosis)

lysosome

fluid filled sac, contains digestive enzymes to destroy unwanted organelles during phagocytosis

plastid

pigmented organelles in plant cells

chloroplast

large organelles with external membrane and layers of folded inner membranes, site of photosynthesis

amyloplast

large and colourless, stores starch grains

chromoplast

large and containing coloured pigments, found in flowers, coloured leaves, fruits and roots

cell wall

on outside of cell membrane, provides structural support, does not regulate movement of substances into cell

primary cell wall

single layer cell wall

secondary cell wall

reinforced structure for further support

histones

protein that makes up chromosomes

apoptosis

programmed cell death

vesicle

package split off of membrane, can be from golgi apparatus or endoplasmic reticulum

SA:V

surface area/volume ratio, smaller, flatter and folded cells have higher SA:V

higher SA:V

absorbs nutrients and gets rid of waste faster

selectively permeable

controls which substances can and can’t enter the cell

fluid mosaic model

model for plasma membrane, made of phospholipid bilayer which flows + changes shape (fluid), and proteins embedded in the bilayer (mosaic)

Phospholipid

Made up of hydrophilic phosphate head and hydrophobic lipid tail, not connected to each other in plasma membrane

hydrophobic

repelled by water

hydrophilic

attracted to water

cholesterol

steroid, holds membrane together and makes it flexible by disrupting bonds between lipid tails

transmembrane proteins

passageways for specific substances to move across membrane

recognition proteins

act as markers to allow immune system to distinguish self cells from non self invaders

receptor proteins

involved in cell communication, bind hormones and other signalling molecules

internal environment

cytoplasm of the cell

external environment

may be in body of water (unicellular organisms) or extracellular fluid (multicellular organisms)

passive transport

transport across membranes without energy use

solution

solvent+solute

solvent

water

solutes

dissolved substances e.g molecules, ions, organic compounds

diffusion

net movement of a solute from a an area of high concentration to low concentration, occurs down/with a concentration gradient

concentration gradient

The difference in concentration between a region of high concentration and a region of low concentration

Osmosis

the diffusion of water molecules across a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration

hypotonic solution

a solution with a lower solute concentration compared to another solution

hypertonic solution

a solution with a higher solute concentration than another solution

Isotonic solution

A solution with an equal solute concentration to another solution

equilibrium

No net movement of solutes (diffusion) or water (osmosis)

lysis

Animal cell bursts when placed in a hypotonic solution e.g pure water

crenation

animal cell shrinks and may die when placed in a hypertonic solution e.g salt water

osmosis in plant cells

cell wall prevents cell from bursting when placed in a hypotonic solution

plasmolysis

cytoplasm shrinks when a plant cell loses too much water by osmosis, cell becomes flaccid

facilitated diffusion

when charged particles and large molecules move through plasma membrane, occurs through transport proteins, passive + with concentration gradient

carrier proteins

bind to specific molecules, change shape and release them on other side of membrane

channel proteins

form passageways for specific ions to pass through, may be able to open and close

active transport

Net movement of substances into and out of a cell against the concentration gradient, requires energy (ATP), involves carrier proteins

endocytosis

allows large particles to enter the cell_, the plasma membrane surrounds the particle, creating a vesicle that moves into the cytosol

pinocytosis

transport of liquids into the cell

phagocytosis

ingestion of large, solid particles into the cell

exocytosis

transports large particles out of cells, vesicles from inside the cell fuse with the plasma membrane and release their contents