Topic 3 Ford Flashcards
Eukaryotic meaning
meaning ‘true nucleus’, have membrane bound organelles
Prokaryotic meaning
meaning ‘no nucleus’, have no membrane bound organelles
Organelle
structure within a cell - the structure will relate to its function
Nucleus
- has a double membrane with pores in it
- contains chromosomes (made of DNA, contain genes that control synthesis of proteins) and a nucleolus
Nucleolus
- darker staining region within the nucleus –> is active so is darker
- dense body where ribosomes are made, makes rRNA and pre-ribosome particles
Ribosomes
- Made of rRNA and proteins
- Can be free in the cytoplasm or attached to the rER
- This is the site of protein synthesis
- In Eukaryotic cells they are 80S (in prokaryotes they’re 70S)
rough Endoplasmic Reticulum
- a system of interconnected membrane bound, flattened sacs
- ribosomes are attached to the outer surface
- Proteins are made on the ribosomes and then transported to other parts of the cell
Cell membrane
-phospholipid bilayer containing proteins and other molecules forming a partially permeable barrier
smooth Endoplasmic Reticulum
- system of interconnected membrane bound, flattened sacs but without ribosomes attached to the surface
- are involved in the synthesis of lipids and steroids
Mitochondrion (Mitochondria - plural)
- have a double membrane, with inner membrane foldings called cristae
- site of later stages of aerobic respiration (where ATP is produced)
- number found in cells depends on energy requirements of the cell
Centrioles
- hollow cylinders made up of a ring of 9 microtubules
- are needed for the formation of the spindle during cell division and in transport within the cytoplasm
- always come in pairs which are placed at 90° to each other
- not found in plant cells
Lysosomes
- spherical sacs containing digestive enzymes bound by a single membrane
- are used to breakdown unwanted substances in the cell and for the destruction of whole cells
Golgi Apparatus
- stacks of parallel, flattened, membrane bound sacs of decreasing size
- they’re formed by the fusion of vesicles from the endoplasmic reticulum
- modifies proteins and packages them into vesicles for transport
- vesicles arrive at the cis face and leave at the trans face
Features of a prokaryotic cell
- contains no nucleus
- no membrane bound organelles
- all unicellular
- have circular chromosomes not associated with histone proteins
- smaller 70S ribosomes
Processes cells need to do:
- make proteins/enzymes
- repair damage
- replicate
- respiration
- storage
- transport
Cells are dynamic
nothing is static; there is continual movement and change
Mitosis
- 2 body cells created
- 46 chromosomes in daughter cells
- 1 division
- not identical to the parent cell
Meiosis
- 4 gametes created
- 23 chromosomes in daughter cells
- 2 divisions
- gives rise to variation
How does genetic variation occur?
Due to random assortment and crossing over. Could also be due to random fertilisation and mutations.
Independent Assortment
Wen the chromosomes pair up with their homologous pair. The way the sister chromatids line up can be different and the DIFFERENT COMBINATIONS OF ALLELES produced creates variation. Variation is caused due to the random alignments of the homologous chromosomes in the first division
Crossing Over
Creates variation by producing chromosomes that contain different combinations of alleles from both parents (molecular scissors). Makes chromosomes that neither parent made; essentially cut and stick
What is the point of intersection between 2 chromosomes in crossing over called?
Chiasma (chiasmata)
Sex Linkage
gene on the X chromosome (males are more likely to have it than females –> they have 2 alleles so have a greater chance of getting a dominant allele to cancel out recessive allele)
Linkage groups
inherit alleles on the same chromosome
Independent inheritance
- genes on separate chromosomes will be inherited independently
- alleles on the same chromosome will be linked and inherited together unless crossing over occurs to separate them
Why is the cell cycle important?
- produces (new cells) growth in multicellular organisms
- replacing/repairing tissues in multicellular organisms
- asexual reproduction in a unicellular organism
How can the cell cycle be split up?
It can be split into 2 parts: Interphase consisting of G1, S and G2 and Division (mitosis)
What happens in G1 (GAP1)?
chromosomes unravel, proteins are made, the cell is growing and organelles are being replicated
What happens in S (synthesis)?
DNA replicates and 2 sister chromatids are made
What happens in G2 (GAP2)?
growth in preparation for cell division
Cell Cycle
I - interphase
P - prophase
M - metaphase
A - anaphase
T - telophase
C - cytoplasmic division (cytokinesis)
Mitosis - Prophase
- chromosomes condense and become visible as 2 sister chromatids join at the centromere
- also a spindle is starting to form
- the centrioles position themselves at opposite ends of the cell (poles) and begin to make spindle fibres between them
What is the widest part of the spindle (cell)?
the equator
Mitosis - Metaphase
- chromosomes line up in the middle of the cell
- the centromeres attach to the spindle fibres along the equator
Mitosis - Anaphase
- the centromeres split so the sister chromatids pull apart
- the poles move further apart and the spindle fibres shorten causing them to move apart
- one chromatid is pulled to each of the poles
Mitosis - Telophase
- each chromosome unravels and 2 nuclei form so the 2 sets of genetic information become enclosed in separate nuclei
- the chromosomes then decondense and the spindle fibres break down
Cytokinesis
- the cell surface membrane constricts around the centre of the cell
- it contracts until the cell is divided into two new cells each with their own nucleus
Centromere
where the 2 chromosomes are joined together
Chromatids
duplicated chromosomes attached at the centromere
What is the name of the process by which bacteria reproduce asexually?
binary fission
Stem cells
an undifferentiated cell that can differentiate (divide and change) into different types of specialised cell
Specialised cell
A cell that has undergone differentiation to carry out a specific job. Can no longer undergo mitosis
Differentiation
The process by which cells become specialised. This can’t be reversed in animal cells
Potency
A measure of how many types of specialised cell a stem cell can make
How many different cell types are there in a human?
216
Pluripotency
Has the potential to develop into most types of cell
Totipotency
Has the potential to develop into all types of cell
Multipotency
Retains the ability to develop into some other types of cell
Zygote
A fertilised egg cell. A single totipotent cell
Embryo
Formed when a zygote divides. It is the group of increasingly specialised cells up to about the 8th week of development
Blastocyst
A hollow ball of cells, containing an inner cell mass which will implant into the lining of the uterus and develop into the multicellular organism
Self-renewal
A property that stem cells have which enables them to make new stem cells to maintain a pool of stem cells for use through an organisms life
Which stem cells are best for use in medicine?
totipotent stem cells as they can develop into any type of cell so they have a great capacity but you need to get them from embryos which causes ethical issues
