save my exams cell theory and eukaryotic cells stucture +speciallisation Flashcards
Robert Hooke
thought to be the first person to view cells (including single-celled microorganisms) and Hooke also came up with the term “cells” to describe these newly discovered structures
cell theory
Matthias Schleiden and Theodor Schwann were two other scientists who studied animal and plant cells
In 1837, they came up with the idea that all living organisms are made of cells
three main ideas f cell theory
All living organisms are made up of one or more cells
Cells are the basic functional unit (i.e. the basic unit of structure and organisation) in living organisms
New cells are produced from pre-existing cells
what cell surface membrane does
controls the exchange of materials between the internal cell environment and the external environment
The membrane is described as being ‘partially permeable’
formed from a phospholipid bilayer
cell wall
formed outside of the cell membrane and offer structural support to cell
polysaccharide cellulose in plants, and peptidoglycan in most bacterial cells
nucleus
all eukaryotic cells
nuclear envelope) which has many pores
contains chromatin
nucleolus-sites of ribosome production
why nucleaur pores are important
important channels for allowing mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes (eg. DNA polymerases) and signalling molecules to travel in
mitochondria
site of aerobic respiration within eukaryotic cells, mitochondria are just visible with a light microscope
Surrounded by double-membrane with the inner membrane folded to form cristae
The matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP
chlorplast
surrounded by a double-membrane
thylakoids containing chlorophyll stack to form structures called grana
photosynthesis
why cholroplast as dna and ribosomes
small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
light dependent stage takes place in
thylakoids
light-independent stage (Calvin Cycle) takes place in
stroma
ribosomes
formed in the nucleolus and are composed of almost equal amounts of RNA and protein
Site of translation (protein synthesis)
Found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells
Each ribosome is a complex of ribosomal RNA (rRNA) and proteins
Rough Endoplasmic Reticulum (RER)
Surface covered in ribosomes
Formed from continuous folds of membrane continuous with the nuclear envelope
Processes proteins made by the ribosomes
Smooth Endoplasmic Reticulum (ER)
Does not have ribosomes on the surface, its function is distinct to the RER
Involved in the production, processing and storage of lipids, carbohydrates and steroids
golgi
The vesicles then transport the proteins and lipids to their required destination
Proteins that go through the Golgi apparatus are usually exported (e.g. hormones such as insulin), put into lysosomes (such as hydrolytic enzymes) or delivered to membrane-bound organelles
lysosomes
orms of vesicles which contain hydrolytic enzymes
Break down waste materials such as worn-out organelles, used extensively by cells of the immune system and in apoptosis
red blood cell adaptions
Red blood cells are biconcave and do not contain a nucleus. This makes more space inside the cell so that they can transport as much oxygen as possible
Cells that make large amounts of proteins will be adapted for this function by containing many ribosomes
neurones
Has a cell body where most of the cellular structures are located and most protein synthesis occurs
Extensions of the cytoplasm from the cell body form dendrites (which receive signals) and axons (which transmit signals), allowing the neurone to communicate with other nerve cells, muscles and glands
The axon (the main extension of cytoplasm away from the cell body) is covered with a fatty sheath, which speeds up nerve impulses. Axons can be up to 1m long in some animals and can therefore enable fast communication over long distances
muscle cells
All muscle cells have layers of protein filaments in them, these layers can slide over each other causing muscle contraction
Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison
three types of muscle cells
skeletal, smooth and cardiac
sperm cells
the head contains a nucleus that contains half the normal number of chromosomes (haploid, no chromosome pairs)
The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
The mid-piece is packed with mitochondria to release energy (via respiration) for the tail movement
The tail rotates, propelling the sperm cell forwards and allowing it to move towards the egg
root
Root hair to increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower)
Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance)
Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
Mitochondria for active transport of mineral ions
xylem
No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
Cells are essentially dead, without organelles or cytoplasm, to allow free movement of water
Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
