The Plasma Membrane and Mitosis (25/10/16) Flashcards
What are the two general functions of the plasma membrane?
It acts as a cell boundary and a cell protecter.
What is the structure of a phospholipid?
- phosphate heads (hydrophilic, charged)
- fatty acid tails (hydrophobic, not charged)
What are the two categories of proteins and how do they differ?
- intrinsic/integral = all the way through the membrane
- extrinsic/peripheral = partway through membrane
What type of protein is always involved in electron transport?
Transport protein.
What is the purpose of cholesterol molecules?
Glue the membrane together - stabalize.
What is auto immune disorder?
When the body doesn’t recognize cells, so the body attacks its own cells. (eg. lupis - caused by sunlight).
What is the backbone of any lipid?
Glycerol.
What is the function of a selective transport channel?
It transports ions/water molecules, and it can be specific towards the type of ion it transports.
What is the function of an enzyme?
It helps a chemical reaction to take place in a cell.
What is the function of a cell surface receptor?
Hormones attach to it to help something take place.
What is the function of the glycoprotein?
They are surface carbohydrates that serve as points of attachment for other cells, bacteria, viruses, toxins, hormones and other molecules.
What is the purpose of cell adhesion?
Cells stick together - for multicellular organisms.
What are the two types of passive transport?
Diffusion and osmosis.
What type of energy does diffusion make use of?
Kinetic energy (temperature).
What are the two types of diffusion?
Simple and facilitated.
What happens during simple diffusion?
Molecules diffuse across the membrane.
What happens during facilitated diffusion?
Channel proteins facilitate molecules across the membrane.
State the change occurring during diffusion.
Molecules go from an area of high solute concentration to an area of low solute concentration until equilibrium is established.
Define osmosis.
The movement of molecules from an area of low solute concentration to an area of high solute concentration until equilibrium is established.
Describe a hypotonic solution.
A solution in which a cell is located which has a low solute concentration compared to the cell. Turgor pressure increases - can burst.
What has a cell undergone when it bursts?
Cytolysis.
Describe a hypertonic solution.
A solution in which a cell is located which has a high solute concentration compared to the cell - cell can shrivel up.
What has a cell undergone when it bursts?
Plasmolysis.
What is it called when the solute concentration is the same on both sides of the membrane - equilibrium?
Isotonic.
Define active transport.
The movement of molecules across a membrane using ATP energy.
List the events of the cell cycle.
Interphase - G1, S and G2
Mitosis - prophase, metaphase, anaphase, telophase and cytokinesis.
What happens during G1 (first growth phase)?
Growth and normal metabolic roles.
What happens during S (synthesis phase)?
DNA replication.
What happens during G2 (second growth phase)?
Growth and preparation for mitosis.
Describe what happens during prophase.
Supercoiling of the DNA to make the chromosome more visible and easier to move around inside the cell.
How is the haploid number represented and what type of cells does it include.
n - gametes (sperms and eggs).
How is the diploid number represented and what type of cells does it include.
2n - somatic cells.
Describe what happens during metaphase.
The chromosomes are pulled down to the equator the centromere replicates.
Describe what happens during anaphase.
New chromosomes called daughter chromosomes migrate to opposite poles.
Describe what happens during telophase and cytokinesis.
The DNA uncoils and the nuclear membrane forms. The membrane then splits into two cells.
How many chromosomes do the daughter cells have in relation to the mother cell?
The same number of chromosomes.
What is a chromatin?
DNA that’s stretched out during interphase. (In the form of chromosomes during supercoiling.
What is a chromatid?
One of the two copies of DNA in a chromosome.
What is a centromere?
The portion of DNA in a chromosome that holds the two chromatids together.
What are centrioles?
The parts related to the production of spindle fibres that facilitate the movement of chromosomes in anaphase.
How many centrioles are in animal cells?
2.
Define equational division.
The process in which the mother cell splits into daughter cells, and the daughter cells have an equal amount of chromosomes as the mother cell.
What were the reasons (3) for the development of the Davson - Danielli model?
- Chemical analysis showed this structure.
- Evidence showed that the plasma membrane has enough phospholipids to double the plasma membrane area - phospholipid bilayer.
- Evidence showed that membranes form a barrier passage - layer of protein.
What pieces of evidence (2) went against the Davson 0 Danielli model?
- There was visible protein IN the phospholipid bilayer.
2. Analysis showed parts of the membrane surfaces were hydrophobic.
What are the functions of polar amino acids?
- Make channels which hydrophilic substances can diffuse through.
- Cause part of the membrane protein to protrude.
What is the function of non-polar amino acids?
Stabilising - force proteins to stay in the membrane.
What process showed that proteins could move within the membrane?
Fusion of cells with the membrane.
What is the significance of the fatty acid tails having a charge?
The attraction of the tails facing inwards makes the membrane stable.
Describe the cholesterol and its purpose.
Mostly hydrophobic, but one end is hydrophilic, so it fits between the phospholipids. Reduces movement (fluidity) of the phospholipid molecules. Also reduces the ability of the membrane to form a magnetic field within itself (permeability), which maintains concentration differences.
When can diffusion occur across a membrane?
When there is a concentration gradient and the membrane is permeable to the particle.
Simply describe the structure and function of potassium channels in axons.
“Ball and chain” - The channel opens when it is depolarized, allowing K+ ions to exit which repolarizes the axon. Ball and chain blocks pore, so it is only open for a short amount of time.
How would you avoid cytolysis or plasmolysis of donar organs?
Bathing the organs in a solution with the same osmolarity as the human cytoplasm. (Eg. isotonic saline - a solution of salts).
Describe endocytosis.
When small pieces of the plasma membrane can be pinched off the create a vesicle that contains some outside material.
Describe exocytosis.
When vesicles move to and fuse with the plasma membrane to release the contents of the cell.
What does the university of genetic coding suggest about the origin of the first cells?
Life evolved from the same original cells that underwent minor differences.
What was Pasteur’s experiments and what did it verify?
He placed broth in flasks and bent the necks in different shapes. He found that fungi and other organisms appeared in the flasks he didn’t boil, and when he snapped off the necks they did. He said that the contact with air caused the spontaneous appearance of organisms.
He verified that cells came from pre-existing cell.
Describe the endosymbiotic theory.
A larger cell takes in a smaller cell and keeps it in a vesicle; in which it continues to perform a function for the larger cell. When the larger cell splits, so does the smaller cell, so the two new cells each have a smaller cell.
What are the two processes during which the process of the endosymbiotic theory happened?
- Cells which don’t need oxygen to live (anaerobic) have an advantage over cells that do need oxygen (aerobic). The aerobic bacteria evolved into mitochondria and then eukaryotes which are now animals.
- Cells that got their energy from complex substances (heterotrophs) took in photosynthetic bacterium and then became autotrophs, or cells that get their energy from simple substances. The autotroph then evolved into chloroplasts which then evolved into plants.
What are the four things the endosymbiotic theory explain about mitochondria and chloroplasts.
- Have naked DNA
- Can grow and divide like cells
- Make and use own proteins
- Have double membranes
What can the mitotic index be used for in the real world?
To predict the growth rate of a tumor.
How does cytokinesis occur in plant cells?
A new cell wall forms across the equator and splits the cell in two.
How does cytokinesis occur in animal cells?
The plasma membrane pinches inwards and splits.
What do cyclins do?
They are proteins that bind to cyclin - dependent kinases enzymes that become active and attach phosphate groups to other proteins in the cell, which carry out tasks specific to the current phase.
How were cyclins discovered and by who?
Tim Hunt discovered cyclins by accident during a protein synthesis investigation; he notices that their concentration corresponded with the phase of the cell.
By what process do tumours form? Explain.
Oncogenesis, with the mutation of oncogenes caused by chemicals called mutagens.
When do primary tumours occur?
When control of the cell cycle has been lost and rapid cell division occurs.
When do secondary tumours occur?
When the cells spread - metastasis.
