Module 3: Voice of the Genome - 3.1 Flashcards
Name organelles in an animal cell
Plasma Membrane, Nucleus, Nucleolus, Nuclear Membrane, Nuclear pore, Chromatin, Centriole, Lysosome, Cytoplasm, Mitochondrian, Ribosome, Rough endoplasmic reticulum, Smooth endoplasmic reticulum, Golgi apparatus, Golgi vesicles
eukaryotic
An organism that has cells containing a nucleus.
Function of the plasma membrane
Controls the exchange of materials between the internal cell environment and the external environment
What is the nucleus?
Big organelle that contains the cell’s DNA and is surrounded by a nuclear envelope.
function of the nucleus
Stores genetic material
what is the Nucleolus
One or more darkly stained regions of the nucleus can be observed under a microscope
function of the nucleolus
Manufacture ribosomes for protein synthesis in the Rough endoplasmic reticulum
what is the Nuclear Membrane
Membrane surrounding the Nucleus ( 2 membranes )
function of the Nuclear Membrane
Keeps the contents of the nucleus, called the nucleoplasm, separate from the cytoplasm of the cell.
what is the Nuclear pore
Are important channels for allowing mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes.
function of the Nuclear pore
Control the flow into and out of the nucleus and check the credentials of all large molecules attempting to pass through.
what is the Chromatin
Material from which chromosomes are made
function of the Chromatin
To package DNA into a smaller volume to fit in the cell, strengthen the DNA to allow mitosis and meiosis.
what is the Centriole
Made of hollow fibres known as microtubules.
function of the Centriole
- Used to move substances around inside a cell, as well as to support the shape of a cell from the inside.
- Two centrioles at right angles to each other form a centrosome which organises the spindle fibres during cell division.
what is the Lysosome
Specialist forms of vesicles which contain hydrolytic enzymes.
function of the Lysosome
To break down waste materials such as worn - out organelles,
Used extensively by cells of the immune system and in programmed apoptosis.
What is apoptosis?
Cell death
what is the Mitochondrian
Small circular pieces of DNA, known as mitochondrial DNA are found in the matrix.
What is the matrix of a mitochondrian
Contains enzymes needed for aerobic respiration, producing ATP.
function of the Mitochondrian
Site of aerobic respiration within eukaryotic cells.
function of the cytoplasm
Holds the components of the cell and protects them from damage.
what is the Ribosome
Can be found as free organelles in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells.
function of the Ribosome
Site of protein synthesis
what is the Rough endoplasmic reticulum ( RER )
Formed from folds of membrane continuous with the nuclear envelope & is covered in ribosomes
function of the Rough endoplasmic reticulum ( RER )
To process proteins made on the ribosomes
what is the Smooth endoplasmic reticulum ( SER )
Similar to RER but with no ribosomes
- Formed from folds of membrane.
function of the Smooth endoplasmic reticulum ( SER )
Involved in the production, processing and storage of lipids, carbohydrates and steroids.
what is the Golgi apparatus
Consists of flattened sacs of membrane similar in appearance to the smooth endoplasmic reticulum
function of the Golgi apparatus
To modify proteins and lipids before packaging them into Golgi vesicles
what is the Golgi vesicle
- Golgi vesicles are membrane - bound, fluid - filled vesicles located in the cytoplasm.
- They are small, round and are seen in a high density near the edges of the sacs
function of the Golgi vesicle
Store and transport modified proteins and lipids from the Golgi apparatus to target cells.
prokaryotic
An organism which has cells that do not contain a nucleus or other organelles surrounded by membranes.
what are Plasmids
Small circular pieces of DNA that replicate independently from the host’s chromosomal DNA.
what is the function of Plasmids
Carry genes for replicating their DNA, transferring themselves from one host cell to another, and for a variety of phenotypes.
what is the Slime Capule
Outer layer of a prokaryotic cell
what is the function of the slime Capule
To protect the bacterium against an immune system attack.
what is the Flagellum
A whip - like structure that allows a cell to move
what is the function of the Flagellum
Assist the cell in movement.
Can both eukaryotic & prokaryotic cells have a flagellum
Yes
what is the Pilus
Short, hair-like structures on the cell surface of prokaryotic cells.
what is the function of Pilus
Involved in adherence to surfaces, which facilitates infection, and is a key virulence characteristic
what are Mesosomes
A convoluted membranous structure formed in a prokaryotic cell by the invagination of the plasma membrane.
what is invagination
The action or process of being turned inside out or folded back on itself to form a cavity or pouch.
what is the function of Mesosomes
Support respiration, and secretion, and enhance plasma membrane surface area and enzyme concentration.
what is Circular DNA
A single, circular chromosome located in the nucleoid region.
what is the function of Circular DNA
A single, circular chromosome located in the nucleoid region.
what are Small ribosomes ( 20nm )
Specialised organelles that are found in eukaryotic & prokaryotic cells.
what is the function of Small ribosomes
Site for protein synthesis
Cell surface membrane
A membrane found either at the surface or inside a cell.
Sperm
A male gamete from a mammal or other animal.
What the sperm contain in the head
- Acrosome: fuses the sperm cell with the cell surface membrane - Contains Lysosomes: filled with digestive enzymes which break down the egg’s zona pellucida & cell membrane.
- Nucleus
Acrosome
An organelle in the head of a sperm that contains digestive enzymes.
What the sperm contain in the middle
- Mitochondria: to provide ATP for flagellar rotation
- Flagellum: enables the sperm to swim - allows mobility
- Very little cytoplasm: increases sperm motility
Ovum
A female gamete or egg cell from an animal.
Organelles in the egg
- Cytoplasm: contains nutrients for growth of the developing embryo
- Haploid nucleus
- Lysosomes: thicken the jelly - like layer, preventing entry of other sperm.
- Follicle cells from ovary: outside the zona pellucida & forms a protective coating around the egg cell.
- Jelly - like coating ( zona pellucida )
- Lipid droplets
- Cell surface membrane
Gametes
sex cells
Gametes in plants
pollen & ovule
what happens during the Acrosome Reaction
- When a sperm reaches the egg cell, it binds to its outer layer ( zona pellucida ) through attachment to sperm - binding proteins.
- The acrosome swells and fuses with the sperm cell surface membrane.
- Digestive enzymes that are contained in the acrosome are released.
- These enzymes digest a tunnel through the follicle and then the zona pellucida so that the sperm can reach the plasma membrane of the egg cell.
- The plasma membranes of the sperm cell and the egg cell fuse and the sperm releases its nucleus into the egg cell cytoplasm.
- The nuclei of the sperm and egg fuse - fertilisation has taken place and a zygote is formed.
what happens during the Cortical reaction
- The fusion of the sperm cell and egg cell stimulates cortical granules to move and fuse with the egg cell surface membrane.
- Cortical granules ( secrete ) release their contents( by exocytosis ) into the zona pellucida.
- These contents react with the zona pellucida causing it to thicken / harden which prevents other sperm cells from entering.
- The sperm and egg cell nuclei then fuse.
Polyspermy
fertilisation by more than one sperm
Mitosis
The process by which the cell nucleus divides to give two new nuclei. Each of these new nuclei has the same number of chromosomes as the original nucleus.
Diploid
Cells or organisms in which the nuclei contain two copies of each chromosome.
steps in Meiosis
- Before division begins both homologous chromosomes replicate ( DNA replication ) forming chromosomes.
- After replication each chromosome is made of 2 strands of DNA, 2 chromatids.
- Meiosis I: Homologous chromosomes pair up as bivalents and then separate.
- Meiosis II - Second division ( similar to mitosis ): Chromatids separate and haploid gametes are formed.
Haploid
Cells or organisms in which the nuclei contain one copy of each chromosome.
Aneuploid
having an abnormal number of chromosomes in a haploid set.
what happens in Independent assortment
- Each gamete ends up with only one of the homologous pairs of chromosomes
- The independent assortment of chromosomes as they line up during meiosis is random and either chromosome from each pair could be in either gamete
- This means gametes can end up with many different combinations of maternal or paternal chromosomes.
Does Independent assortment occur in meiosis I or meiosis II?
In meiosis I
What happens in crossing over?
- Homologous chromosomes come together as pairs and all 4 chromatids come into contact.
- At these contact points, chromatids break and rejoin exchanging sections of DNA between non - sister chromatids.
- The point where the chromatids break is called a Chiasma ( chiasmata ).
- Many chiasmata may form anywhere along the length of the chromosome leading to chromosomes containing new combinations of alleles from both parents.
- This results in genetic variation.
Crossing over does NOT occur between the sex chromosomes.
When does crossing over occur meiosis I or meiosis II
meiosis I
Describe and explain how, in mammals, events following the acrosome reaction prevent more than one sperm fertilising an egg.
- Once the sperm fuses with the egg membrane, this stimulates the cortical granules to move towards the zona pellucida.
- The cortical granules release their contents into the zona pellucida via exocytosis.
- This causes the zona pellucida to thicken, preventing the entry of other sperm cells.
- The fusion of the sperm nucleus and the egg nucleus produces a zygote.
Animals produce haploid gametes by meiosis.
Explain how meiosis gives rise to genetic variation in gametes. [2]
- Crossing over involves swapping of sections of chromosomes.
- Independent assortment because the assortment of chromosomes can be random and therefore different combinations of DNA in gametes
Males produce large numbers of sperm cells each with a different genotype.
Describe how the variation in sperm cell genotype arises.
Variation is produced in meiosis, as a result of crossing over of alleles between chromatids, the independent assortment of chromosomes.
What can also lead to variation
Random fertilisation
What occurs during protein trafficking?
- Transcription of DNA to mRNA.
- mRNA leaves the nucleus.
- Protein made on ribosomes enter the rough endoplasmic reticulum ( RER )
- Protein moves through the ER assuming 3D - shape en route.
- Vesicles pinched off the RER contain the protein.
- Vesicles from RER fuse to form the flattened sacs of the golgi apparatus.
- Proteins are modified within the golgi apparatus.
- Vesicles pinched off the golgi apparatus contain the modified protein.
- Vesicle fuses with cell surface membrane releasing protein, such as extracellular enzymes.
Zygote
fertilised egg
Fertilisation
The process in which a male gamete fuses with a female gamete to form a zygote.
Chiasma
The place where chromosomes can be seen to cross over each other in a cell undergoing meiosis.
