topic 2 Flashcards
describe the rough endoplasmic reticulum and function
- series of singular flattened sacs enclosed by a membrane - synthesise and modify - ribosomes on the surface - proteins and glycoproteins are made here
describe the smooth endoplasmic reticulum and function
- series of single tubular sacs made of membrane - synthesise and modify substances - lipids and carbohydrates made here ,stores and transported
describe the Golgi apparatus and function
- a series of single curved sacs enclosed by a membrane known as cisternae - transport vesicles mostly from the rough ER, fuse with Golgi A at cis face , mature into cisternae and pass through - modify protein and packages them in secretory vesicles for transport to correct area of cell or indeed secreted
describe the lysosome and function
- enclosed by single membrane and contains digestive enzymes (eg. protease)
1) autolysis (self splitting) - cell so badly damaged no function eg. cancer cell, cell programmed to self destroy or when cell naturally dies or during differentiation releases enzymes into cytoplasm to destroy
2) exocytosis (secretion) - lysosome membrane fuse with cell membrane, enzymes released into gland duct or interstitial fluid
3) autophagy (break down of broken organelles) - inject enzymes into organelle, digest , use material again
4) incorporation - something comes into cell eg. bacteria , binds , releases enzymes and digest
describe the nucleus and function
sets prokaryotic and eukaryotes apart, double bounded membrane known as nuclear envelope with nuclear pores which allow the passage RNA out of cell. - inside the nucleus is the nucleolus where ribosomal RNA is manufactured and contains DNA and RNA, also thought to control activity of cell by ‘turning genes on and off’
describe the microvilli and function
small protrusions on the plasma membrane on outer surface of some cells. supported by actin filaments which act as a structural core - increase the SA involved in absorption and secretion
describe the cytoplasm and function
primarily water with sugars and salts dissolved, large molecules like fats and proteins in suspension, some proteins may be enzymes - chemical reactions happen here , in living plant and fungal cells cytoplasm is often seen to move, carrying substances throughout the cell (cytoplasmic streaming)
describe the cell wall in plant cells and function
tough external layer gives greater structural strength as well as providing mechanical strength in order to stop cell bursting from osmotic entry of water - cellulose and pectin matrix to stop stretching and snapping
describe the plasma membrane and function
forms a thin boundary enclosing the cell , made up of phospholipid bilayer with additional components such as proteins, glycoproteins and cholesterol - controls entry and exit of materials
describe the ribosomes and function
site of protein synthesis within the cell. made up of two subunits (large and small subunit both comprised of ribosomal RNA and protein) - Prokaryotic are known as 70s ribosomes and eukaryotic are known as 80s ribosomes - messenger RNA from nucleus enters ribosome and is translated into protein
define mitosis
Mitosis is the process of cell division in which a single parent cell divides to produce two genetically identical daughter nuclei. These daughter cells will have the same number of chromosomes and the same genes/alleles as the parent cell.
name the stages of mitosis
Whilst mitosis is a continuous process we can identify four different stages by the behaviour and position of the chromosomes. The stages are as follows: Interphase (not strictly mitosis) Prophase Metaphase Anaphase Telophase
define and explain interphase
Interphase is the period in which the cell is not dividing. Most of a cell’s time is spent in interphase (c. 90%)
First growth phase (G1) where the cell synthesises the proteins required to make new organelles
Synthesis (S) phase where the cell replicates its DNA
(G2) where organelles divide and the cell increases its stores of energy for the division to follow.
Cells in interphase can be recognised by the absence of visible chromosomes.
define and explain prophase
Prophase is the first stage of mitosis. During prophase the chromosomes become visible. In addition the nuclear envelope and nucleolus disappear. Centrioles move to opposite poles of the cell and spindle fibres begin to form. Cells in prophase can be identified by their visible chromosomes which lack any definite pattern or organisation.
define and explain metaphase
During metaphase the chromosomes line up along the middle (or equator) of the cell. The spindle fibres from the centrioles are fully formed and attach to the centromeres on each chromosome. Only when all the spindle fibres are attached to the centromeres does the cell progress to the next stage.
define and explain anaphase
During anaphase the spindle fibres contract pulling the sister chromatids apart and towards the poles of the cell. Anaphase is recognisable by the clearly defined chromosomes moving apart.
define and explain telophase
As the chromatids reach the opposite poles of the cell they become less visible. The nuclear envelopes and nucleoli reform around each set of chromatids. The spindle fibres disintegrate. During telophase the cell splits into two in a process known as cytokinesis
describe and explain the three functions of mitosis
Growth – from a single fertilised egg to a fully-grown organism requires that each cell be genetically identical. Mitosis allows this to happen.
Differentiation – all cells are not the same i.e. liver cells, skin cells, nerve cells. After these cells differentiate they divide by mitosis to form tissues made up of identical cells.
Repair – Mitosis allows new cells to replace exactly the cells which have been lost or damaged
how is cancer linked to mitosis
Cancer is a condition whereby the normally carefully controlled cell cycle goes wrong and cell division proceeds uncontrollably. This normally occurs as a result of damage to the genes which control the cell cycle. The result is a mass of abnormally dividing cells known as a tumour which continues to grow in size. In some instances cancerous cells may spread around the body and form secondary tumours. This is known as metastasis.
what are differences mitosis and meiosis
Mitosis Produces two genetically identical daughter nuclei with the same chromosome number (the diploid number). Is involved in growth and repair in organisms Meiosis Produces four daughter nuclei each with half the chromosome number of the parent cell (the haploid number). Each daughter nuclei is genetically varied Is involved in sexual reproduction (production of gametes)
why is meiosis useful
Meiosis halves the chromosome number in the gametes from the diploid number (46 in humans) to the haploid number (23 in humans). This is necessary as otherwise the offspring formed from two gametes would have double the number of chromosomes as the parents. Meiosis introduces genetic variation into a population via independent segregation and genetic recombination by crossing over.
what are the stages of meiosis
have two stages: meiosis I and meiosis II, each involves the division of nuclei and cells (cytokinesis) also has the same stages of mitosis PMAT x2 however extra steps to produce variation (only in meiosis I)
what is the structure of prokaryotes
what are the structures of eukaryotes
