Cells Part 2 ( Cell Cycle, Mitosis, Trasnport Across Cell Membrane) Flashcards
Describe Binary fission
Replication of circular dna - cell gets bigger, both copies starch to cell membrane
Replication of plasmids
Cell membrane grows and begin to pinch inwards
Division of cytoplasm to produce daughter cells
What does the cell cycle consist of
Interphase, mitosis, cytokines
What happens during interphase
Cell growth and replication
Chromosomes replicated - chromatids
Chromatin- chromosome - chromatids
What is prophase
Nuclear membrane and nucleolus break down
Chromosome condense
Centrosomes move to opposite ends of nucleus where they form poles
What is metaphase
Centromeres attach to spindle fibres
Chromosomes/ pairs of chromatids line up at the equator of the spindle/ cell- attached by their centromeres
No nuclear envelope
What is anaphase
Centromeres divide
Chromatids pulle dot opposite poles/ end sof cell
Spindle fibres shorten
What is telophase and cytokinesis
Sister chromatids reach opposite sides and decondense
Nuclear membrane and nucleoli reform
What is a telomere
Repetitive dna sequences at the end of a chromosome
Protects the end of chromosome from being frayed/ tangled
What is metastasis
Spreading of malignant/ cancerous tumour
By apricots eof tumour breaking off and travelling in blood/lymph
Forms a secondary tumour
Greatly reduced survival chances
Describe and explain what a student should to when counting cells to make sure the mitotix index was o accurate
- Examine large number of felds of view i many cells:
Mark as pairs only
Accept large number / 20 or more for many - To ensure representative sample;
Accept typical / reliable
OR - Repeat count;
4.To ensure figures are correct;
OR
5. Method to deal with part cells shown at edge /count only whole cells;
6. To standardise counting:
What is the purpose of of the cell-surface membrane
Boundary between cytoplasm and the environment
Border and allows cells to interact with their environment in a controlled way
Moves substance sin and out of cell
What is the function of the phospholipid bilayer
Allow lipid soluble, prevent water soluble
Make membrane flexible
Small, non-polar, lipid soluble
Describe how the phospholipid bilayer forms
Fatty acid/ hydrophobic tails pointing in each other
Phosphate/ polar/ hydrophilic heat pointing out - insert city water
When does the fluidity of the membrane increase
Temp and number of double bonds increase
Decrease cholesterol
Why is it called a fluid mosaic model
Phospholipids cna move relative to each other
Proteins vary in size
What are extrinsic proteins
On the surface/ partly embedded
Mechanical support
Act as receptors
What are intrinsic proteins
Completely span the membrane
What are the functions of proteins in a cell membrane
Provide support
Carry wat ersoluble ubstances
Allows active transport
Form recognition sites
Help cells adhere together
Act as receptors
What is the function of cholesterol in a cell -membrane
Reduce lateral movement for meolciles
Make membrane less fluid at higher temperatures
Prevent leakage eof water and dissolved ions
What are the functions of glycolipids
Act as recognition sites
Maintain stability of the membrane
Help cells attach to one another and so form tissues
What are the functions of glycoproteins
Recognition sites
Helps cells attach to one another and form tissues
What is Exocytosis
Secrets substance outside of cell by releasing them from a vesicle
Fuse with plasma membrane
What is endocytosis
Cells takes ins substance by invagination a portion of the plasma membrane and forming vesicle around the substance
What is pinocytosis
Absorbing dissolving material
Cell gulps droplets of fluid by forming tiny vesicles
What is diffusion
The movement of particles from a region of high concentration to an area of low concentration (down a concentration gradient) until evenly spread. The particles that pass through must be small, lipid soluble, and uncharged. It is a passive process that requires no input of energy in the form of ATP
What factors does diffusion depend on
It depends upon;
- the membranes composition
- Number of pores
- Size of diffusing molecules
- Whether its lipid soluble
- Whether its polar
Concentration gradient
Temperature
Sa
Diffusion difference
What is facilitated diffusion
the movement of particles down as concentration gradient using channel or carrier proteins. This is when the diffusion is evenly spread up by specific proteins in the cell membrane, however it can be limited by the number of proteins. Only energy used is kinetic energy that the molecule already has, its a passive processes. Occurs at channels on the membrane where there are special carrier molecules
It occurs down the concentration gradient and doesn’t require energy. It transports substances, such as glucose, that aren’t lipid soluble
What are carrier proteins
Take substances from one side to another
What are channel proteins
Protein pores that open and close
What is osmosis
Osmosis is the movement of water molecules from a solution with a higher water potential to a solution with a lower water potential through a partially permeable membrane
What is water potential
Water potential, psi, is a measure of how easy it is for water to move. The more water molecules there are present the more easily they can move so the higher the water potential. Water potential is measured in units of pressure, usually kilopascals
Distilled water has a greatest number of water molecules in a given volume as it is pure water- we say it has the water potential has 0. All other solutions will have a value less than 0- they will always be negative
What protein channels do water move through
Aquaporin
What is hypotonic
Higher water potential
Water enter cells- burts and swells
Plant cells- turgid (cell wall)
What isotonic
Equal water potential so water neither enters nor leaves
What is hypertonic
Lower water potential
Water leaves cell
Shrinks
Plants- plasmolysised
What is active transport and describe the process
Active transport is the movement of molecules or ions into or out of the cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins
- Molecule or ion being transported binds to receptor sites on the carrier protein
- On the inside ATP binds to the carrier protein and splits into ADP and a phosphate molecule
- The carrier protein changes shape and opens up on the opposite side, releasing the molecule/ion to the other side of the molecule
- The phosphate molecule is released from the carrier protein, causing it to revert back to its original shape. ADP + Pi recombine during respiration to form ATP
What is cotransport
2 different substances involving carrier proteins
Uses atp
Sodium ion and proton bind to protein
Protein changes shape to move sodium ion and proton across cell membrane
- Sodium ions actively transported from ileum
cell to blood; - Maintains / forms diffusion gradient for sodium
to enter cells from gut (and with it, glucose); - Glucose enters by facilitated diffusion with
sodium ions;
Factors affecting the rate of absorption
- The concentration of glucose
- Temperature
- Amount of protein channels/ carriers
- Amount of co-transport proteins
Explain how a tissue loses mass
1.Water potential of solution is less than / more negative than that of potato
tissue; Allow Ψ as equivalent to water potential
2. Tissue loses water by osmosis
Why do membranes of white blood cells have less cholesterol
Membrane less rigid and more fluid
Fit through openings in capillaries
Attracted by chemicals for immune response - chemotaxis
What does histamine do
Dilates blood vessels
Increases permeability of capillary wall
