Unit 1: Section 3 - Cell Division, Diversity and Organisation Flashcards
What is the cell cycle?
The process of cell growth and division
What are the 5 stages of mitosis?
Interphase Prophase Metaphase Anaphase Telephase
What happens in interphase?
The cell prepares to divide
Cells DNA is unravelled and replicated, to double its genetic content
organelles replicated so it has spares
ATP content increased in preparation for cell division
What happens in prophase?
Chromosomes condense, getting shorter and fatter
centrioles move top opposite ends of the cell forming a network of proteins fibres across it called the spindle
Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
What happens in metaphase?
Chromosomes line up along the middle of the cell and become attached to the spindle by their centromere.
What happens in anaphase?
Centromeres divide, separating each pair of sister chromatids.
The spindles contract, pulling chromatids to opposite ends of the cell, centromere first
What happens in telophase?
Chromatids reach the oppsosite poles
They uncoil and become long and thin
A nuclear envelope forms around each group of chromosomes so there are 2 nuclei.
Cytoplasm divides to make 2 new cells (cytokinesis)
How can you observe mitosis under a microscope?
Stain the chromosomes,
How do yeast cells reproduce?
asexually by budding
What are the 5 stages of budding?
1) A bud forms at the surface of the cell
2) The cell undergoes interphase
3) The cell undergoes mitosis
4) Nuclear division is complete - the budding cell contains a nucleus that has an identical copy of the parent cell’s DNA
5) Bud separates off from the parent cell, producing a new, genetically identical yeast cell.
What happens when two gametes join together?
They form a zygote
What happens in meiosis?
1) DNA replicates
2) Chromosomes arrange themselves into homologous cells
3) Chromosome pairs then swap ‘bits’ with each other
4) In the first division, these homologous pairs split up. Any one chromosome from each pair can go into either cell.
5) In the second division each chromosome splits in half
6) Four new genetically different cells are produced
7) They are genetically different.
What are homologous pairs of chromosomes?
Chromosomes that have the same genes, although they could have different versions (alleles) of those genes
What are stem cells?
Unspecialised cells - they can develop into any type of cell
Where are stem cells found in adults and embryos?
Adults - Bone marrow (but not as flexible as in embryos)
Embryos - In the first few days of an embryos life, any of it’s cells can turn into any cell.
What is the diploid number?
The number of chromosomes in the body cells of species (in humans it is 46)
What is the haploid number?
The number of chromosomes in gametes in a species (half the diploid number)
How are stem cells used in humans?
Adult stem cells are used to replace damaged cells e.g. new skin or blood cells
How are stem cells used in plants?
Stem cells are needed to make new roots and shoots as they are constantly growing
Where are plant stem cells found?
In the cambium
How are neutrophils adapted to perform their function?
Neutrophils defend the body against disease, they have a flexible shape which allows them to engluf foreign particles or pathogens. They also contain lots of lysosomes in their cytoplasm which contain digestive enzymes to break down engulfed particles.
How are erythrocytes adapted to perform their function?
Erythrocytes carry oxygen in the blood, their biconcave disc shape provides a large surface area for gas exchange. They have no nucleus so there’s more room for haemoglobin
How are epithelial cells adapted to perform their function?
Epithelial cells cover the surface of organs, The cells are joined by interlinking cell membranes and a membrane at their base. Some epithelia (e.g. in the lungs) have cilia to move particles away. Other cells (e.g. small intestine) have microvilli (folds in the cell membrane to increase surface area)
How are sperm cells adapted to perform their function?
They have flagellum so they can swim to the egg, they also have lots of mitochondria to provide energy to swim
How are paliside mesophyll cells adapted to perform their function?
They do most of the photosynthesis, they contain many chloroplasts so they can absorb a lot of sunlight, they walls are thin so CO2 can easily diffuse into the cell.
How are root hair cells adapted to perform their function?
absorb water and minerals from soil. Large surface area and thin, permeable cell wall. Cytoplasm has extra mitochondria to provide more energy for active transport.
How are guard cells adapted to perform their function?
They line the stomata (tiny pores in the leaf used for gas exchange). In the light, guard cells take up water and become turgid. Their thin outer walls and thickened inner walls force them to bend outwards, opening the stomata.
What is a tissue?
A group of cells that are specialised to work together to carry out a particular function
What is the squamous epithelium tissue?
A single layer of flat cells lining a surface. Squamous epithelium tissue is found in many places including alveoli in the lungs.
What is the xylem tissue?
A plant tissue with 2 jobs…
1) Transports water around the plant
2) Supports the plant
It contains xylem vessel cells and parenchyma cells
What is the ciliated epithelium tissue?
A layer of cells covered in cillia. It’s found on surfaces where things need to be moved e.g. in the trachea.
What is the phloem tissue?
Transports sugars around the plant. Arranged into tubes and is made up of sieve cells, companion cells and ordinary plant cells. Each sieve cell has end walls with holes in them so that sap can move easily through them. These end walls are called sieve plates.
What is an organ?
A group of tissues that work together to perform a particular function e.g. lungs, leaves
2 examples of an organ system
Respiratory system and circulatory system
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