F211 Cell Division, Cell Diversity, Cellular Organisation Flashcards
Interphase
Phases
Growth 1
Synthesis
Growth 2
Cell Cycle
Nuclear division, mitosis, is only a very small part of the cycle, a third of the other three phases
Growth 1, Synthesis, Growth 2, take up a third each of the rest of the cycle
Interphase
Growth 1
First and longest growth stage
Organelles produced
Cytoplasm volume increases
46 chromosomes
Interphase
Synthesis
Chromosome replication
DNA content doubles
92 chromosomes
Interphase
Growth 2
Second growth phase
Cytoskeleton breaks down
Checks that the copied DNA is correct
Mitosis
Phase
Prophase
Metaphase
Anaphase
Telophase
Prophase
Chromosomes shorten and thicken, coil around histones
Nuclear envelope breaks down and disappears
Centriole divides in two
Each daughter centriole moves to the opposite poles of the cell
Centrioles organise the spindle, a 3D structure made of microtubles
Metaphase
Chromosomes move to the central region of the spindle, the equator
Each chromosome becomes attached to a spindle thread by its centromere
Anaphase
Replicated chromatid pairs separate when the centromere holding them together splits
Spindle fibres shorten pulling the sister chromatids away from each other towards the poles
They assume a V shape because they are pulled by their centre
Telophase
The separated chromatids reach the poles of the cell
A new nuclear envelope forms around each set of chromosomes
The spindle breaks down and disappears
The chromosomes uncoil
Cytokinesis
Cell division
Takes place after mitosis
Cytokinesis
In Animal Cells
The membrane constricts around the middle of the cell
A ring of protein filaments bound to the surface of the cell membrane contract until the cell is divided into two, actin and myosin
The daughter cell is genetically identical to the parent cell
Cytokinesis
In Plants
Only happens at meristems
A new cell wall plate is synthesised between the two new cells where the spindle was
Homologous Pair of Chromosomes
Chromosomes that have the same genes at the same loci
Pair up during meiosis
One chromosome from each parent
Made up of genes that code for the same thing
Purposes of Mitosis
Produces cells which are genetically identical to the parent and can therefore perform the same function. This is used for: Asexual Reproduction Growth Repair Replacement
Purpose of Mitosis
Asexual Reproduction
Single called organisms divide to produce two daughter cells that are separate organisms
Some multicellular organisms produce offspring from parts of the parent
Purpose of Mitosis
Repair
Damaged cells need to be replaced by new ones that are identical so they can do the same function
Purpose of Mitosis
Growth
Multicellular organisms grow by producing new extra cells
Each new cell is genetically identical to the parent so can perform he same functions
Purpose of Mitosis
Replacement
Red blood cells and skin cells are replaced by new ones
Budding in Yeast
Growth 1
Synthesis - budding begins as DNA replicates
Growth 2
Mitosis
Cytokinesis, the bud separates from the parent cell
Products of Meiosis
4 gametes
Not genetically identical
Contain half the genetic material / number of chromosomes
Stem Cell
Undifferentiated cells that are capable of becoming differentiated to a number of possible cell types
Totipotent
Differentiation
Definition
The development and changes seen in cells as they mature to form specialised cells
Differentiation
Erythrocytes (Red Blood Cells)
Produced form undifferentiated cells in bone marrow
Lose their nucleus, mitochondria, golgi body and rough endoplasmic reticulum
Packed full of protein haemoglobin
Shape changes to be bio concave
Allows them to triplet oxygen efficiently in the blood
Differentiation
Neutrophils
Differentiated from stem cells in the bone marrow
Produce enormous numbers of lysosomes
To produce enzymes to digest engulfed microorganisms
Differentiation
Phloem Sieve Tubes
Differentiated from cambium
Cells elongate and line up end to end to form a long tube
Ends of cells do not break down completely but form sieve plates which allow the movement of materials up or down the tubes
Differentiation
Xylem Vessels
Differentiated from cambium
Small cells that elongate
Walls become reinforced and waterproofed by lignin which kills the contents of the cell
Ends of the cell break down so they become a continuous long tube with a wide lumen
Able to transport water and minerals and helps to support the plant
Cambium
A type of meristem cell
Requirements for Photosynthesis
Light
A supply of water
A supply of carbon dioxide
The presence of chlorophyll
Specialisation
Erythrocytes
Contains Haemoglobin for oxygen to bind to
Few organelles to make space for haemoglobin
Bio concave shape increases surface area to allow more often to bind
Specialisation
Neutrophils
Large numbers of lysosomes to produce enzymes to digest engulfed microorganisms
Specialisation
Epithelial Cells
Squamous - flattened cells reduces distance for diffusion, able to form a smooth flat surface so they are ideal for the insides of tubes where fluids can pass easily over them
Ciliated- covered in tiny projections called cilia which are able to waft substances (e.g. mucus) past the cell
Specialisation
Sperm Cells
Many a mitochondria for energy from respiration so they can move more
Specialised lysosome, acrosome, in the head that released enzymes onto the outside of the egg allowing the sperm to penetrate and fertilise the egg
Small long and thin to ease their movement
Single long undulipodium (tail) to propel the sperm towers the egg
Specialisation
Palisade Cells
Contain lots of chloroplasts to collect more light energy
Specialisation
Root Hair Cells
Hair like projections increases surface area so that more water and minerals can enter the cell
Large vacuole to store minerals
Specialisation
Guard Cells
Appear in pairs on the lower epidermis of leaves
Contain chloroplasts and cell walls contain spiral thickenings of cellulose
When water moves in the cells become turgid and because of the spirals only the outer walls stretch
Two guard cells bulge at both ends so the pore, stomata, opens
Tissue
Definition
A group of similar cells that work together to perform a particular function
Organ
Definition
A collection of tissues that work together to perform a particular function
Organ System
Definition
A number of organs working together to perform an overall life function
