Cells Flashcards
What do cells make up ?
Tissues - Organs - Organ systems - Organism
What are the necessary features of living organisms?
Movement - change position
Respiration - release energy from food
Sensitivity - respond to things
Growth - gets bigger
Reproduction - makes copies of itself
Excretion - remove waste material
Nutrition - consumes chemical material
What does the cell membrane do ?
Controls what passes in and out of a cell
What does the cell wall do ( plants ) ?
Gives the cell strength - made up of cellulose which is strong
What does the vacuole do ( plants ) ?
Contains sap, helps support shape of cell
What do chloroplasts do ( plants ) ?
Contain chlorophyll, needed for photosynthesis
What do ribosomes do ?
Make protein - protein synthesis
What does the nucleus do ?
Controls activities of the cell
Contains DNA
What does cytoplasm do ?
Where most of the chemical reactions take place
What does mitochondria do ?
Where aerobic respiration takes place
What is a eukaryotic cell ?
Plant cell, fungi cell or animal cell
What is a prokaryotic cell ?
Bacteria or archaea cell
Size of eukaryotic cell
5 - 100 micrometres
Size of prokaryotic cell
0.2 - 2 micrometres
Where is the genetic material of a eukaryote found ?
In a nucleus
Where is the genetic material of a prokaryote found ?
A single molecule, found free in the cytoplasm - circular DNA
May have extra rings of DNA called plasmids.
What do eukaryotic cells contain that prokaryotic cells do not ?
Membrane-bound organelles
How do eukaryotic cells divide ?
Mitosis
How do prokaryotic cells divide ?
Binary fission
What is magnification ?
The ability of a lens or other optical instrument to enlarge the size of something.
Equation for magnification
Total magnification = magnification of eye piece x magnification of objective lens
What is an electron microscope ?
A microscope that uses a beam of electrons as a source of illumination. They use electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam.
Transmission electron microscopes
Used to look at extremely thin sections of cells. Highest magnification obtained from a TEM is 1,000,000x.
Scanning electron microscopes
Work by bouncing electrons off the specimen that had an ultra-thin coating of heavy metal applied.
Used to reveal the surface shape of structures such as small organisms and cells.
Resolution and magnification is lower than in TEMs
Pros of electron microscopes
High magnification
High resolution
Ability to see inside cells
Cons of electron microscopes
Expensive
Cells have to be dead
Not portable
Need training to use
No colour
Slides have to be made in a vacuum
Resolution definition
The ability of a microscope to distinguish 2 points as separate from one another.
Pros of light microscopes
See colour
Affordable
Easy to use
Portable
Specimen can be living
Cons of light microscopes
Low magnification
Low resolution
Micrometre in metres
0.000001 metres ( -6 )
Nanometre in metres
0.000000001 metres ( -9 )
What is a specialised cell ?
When cells or tissues become adapted to carry out their specific function
What is differentiation ?
When cells gain certain features needed for their functions ( when they have become specialised )
Muscle cell function
Contraction for movement
Ciliated epithelial cell function
Line the airways and protect from pathogens
Root hair cell function
Absorption of water and minerals from soil
Egg cell function
A gamete used in sexual reproduction
Fat cell function
Acts as an energy store
Phloem cell function
Transport of dissolved sugars and amino acids
Xylem cell function
Transport tissue for water and mineral ions
Palisade cell function
Carry out photosynthesis in the leaves
Red blood cell function
To transport oxygen around the body
Nerve cell function
To carry electrical impulses around the body
Sperm cell function
A gamete used in sexual reproduction
Guard cell function
Open and close the stomata to allow gas exchange in plants
Cone cell function
To allow colour vision
Adaptations of muscle cells
Contain filaments that contract
Lots of mitochondria to provide sufficient energy for muscle contraction
Adaptations of ciliated epithelial cells
Mucus is made by goblet cells, mucus trap pathogens
Contains cilia which waft mucus
Adaptations of root hair cells
Has a projection to increase surface area
Thin walls for short diffusion distance
No chloroplasts
Adaptations of egg cell
Contains a nucleus with half the number of chromosomes
Cell membrane changes after fertilisation so sperm cannot enter
Adaptation of fat cells
Contains a fat store which can be broken down to release energy
Can increase in size to store more fat
Adaptation of phloem cells
Joined end to end to make a tube
Few organelles to aid the flow of materials
Adaptation of xylem cells
Line up in tubes and the individual cell walls break down to make xylem vessels
Contains lignin, which strengthens the vessel
Adaptations of palisade cells
Contain many chloroplasts
Chloroplasts are found near the top of the cell, where the most light is found
Adaptations of red blood cells
No nucleus to create more space for oxygen
Large surface area
Adaptations of nerve cells
Long and thin to carry for long distances
Lots of mitochondria to release large amount of energy
Adaptation of sperm cells
Nucleus has half the number of chromosomes
Acrosome in the head contains enzymes to break down outer layer of egg cell
Adaptation of guard cells
Found in pairs
Change shape to open and close the stomata
Adaptation of cone cells
Contains visual pigment
One end usually links up to a nerve cell so our body can respond to visual stimuli
What are stem cells ?
Undifferentiated cells which are capable of self-renewal to produce more stem cells ( via mitosis ) or differentiate into specific specialised cells.
Where are embryonic stem cells found ?
In 3-5 day old embryos
Where are adult stem cells found ?
Rare and only found at specific locations eg bone marrow
Where are umbilical cord stem cells found ?
In the umbilical cord, which has a rich source of stem cells formed from the placenta
What can embryonic stem cells differentiate into ?
Any type of cell
What can adult stem cells differentiate into ?
Cells from the type of tissue they were found in
What can umbilical cord stem cells differentiate into ?
Blood cells - used to treat blood disorders
Therapeutic cloning
An embryo is produced with the same genes as the patient. Stem cells from the embryo are collected and used to treat the patient, as they won’t be rejected
What is the meristem ?
A layer of unspecialised stem cells in a plants roots and shoots. They have the ability to become any type of plant cell.
Why are plant stem cells useful ?
Clones can be made quickly and efficiently - rare plants can be grown to avoid extinction
Produced to sell - economic benefit
Crops with ideal features like disease resistance can be clones
For research
Food
Medicinal properties
What is mitosis ?
Cell division that results in genetically identical diploid cells
What is mitosis used for ?
Growth and development of tissues in multicellular organisms
Repair of tissues in multicellular organisms
Asexual reproduction in multicellular organisms + binary fission in unicellular organisms
- Interphase - G1
Sub cellular structures duplicate eg ribosomes and mitochondria
- Interphase - S
DNA replicates to form 2 copies of each chromosome, each chromosome consisting of 2 sister chromatids, connected in the centre by a centromere.
- Interphase - G2
DNA is checked for errors made during replication. Done using enzymes, and any error can be fixed.
- Mitosis
The chromosomes move to opposite poles of the cell and two nuclei form
- Cytokinesis
Cytoplasm divides and cell membrane separates, creating 2 new genetically identical daughter cells
- G0
Temporary cell resting. Some cells eg nerve cells will never divide again
Mitosis 1.Prophase
DNA condenses
Nuclear membrane disappears
Spindle fibres form from centrioles
Mitosis 2.Metaphase
Chromosomes line up at the equator
Spindle fibres attach to chromosomes
Mitosis 3.Anaphase
Chromatids are pulled apart, by spindle fibres and motor proteins, towards poles
Mitosis 4.Telophase
Nuclei form around the chromosomes
Spindle fibres disintegrate
