Cell Biology Flashcards
What is cell theory?
All living organisms are composed of cells
Cells are the smallest units of life
Cells only come from pre-existing cells by cell division
What do all cells have?
Cytoplasm
Cell membrane
DNA
Ribosomes
What are the exceptions of cell theory?(Explain)
Striated Skeletal Muscles Fibres= very long cells with many nuclei
Aseptate fungi= each hyphae is undivided and has many nuclei
Giant algae= grow very large but are unicellular
Define magnification
Ability to make an object larger
Define resolution
Ability to distinguish separate parts of an object/two objects from each other
Compare an EM microscope vs. a Light microscope
EM has higher resolution, higher magnification
BUT, expensive, difficult sample preparation, cannot image living organisms
For each of the following state whether they are prokaryotes or eukaryotes and state whether they are unicellular or multicellular:
Bacteria
Protoctista
Fungi
Animals
Plants
Bacteria- Prok, uni
Protoctista- Euk , mostly uni
Fungi- Euk, multi except for yeast
Animals- Euk, multi
Plants-Euk, multi
Give two features of a prokaryotic cells
Unicellular
No compartmentalisation
What does compartmentalisation mean?
No membrane- bound organelles
Draw a prokaryotic cell and label it fully.
Must have:
70S ribosomes
cell/plasma membrane
cell wall
DNA/genetic material
pili
cytoplasm
flagellum
What is the genetic material of a prokaryotic cell?
1 circular naked chromosome in Nucleoid
What are pili used for?
Adhesion and conjugation
Draw an animal cell and label it fully.
Rough ER
Mitochondrion
Nucleus
Nuclear envelope
Golgi apparatus
vesicle
cytoplasm
80s ribosomes
cell membrane
nuclear pore
What are the differences between plant and animal cells?
Plants have chloroplasts animals do not
Plants have cell walls animals do not
Plants have a large and permanent vacuole animals have small and temporary
Most plants do not have centrioles animal cells do
Draw a mitochondria and a chloroplast
Double membrane!
Distinguish between prokaryotic and eukaryotic cells
- Naked DNA; DNA associated with histone proteins
- Circular DNA, linear DNA
- DNA in nucleoid; DNA in nucleus
- 1 chromosome; 2 or more different
- no membrane bound organelles; yes
- 70S ribosomes; 80S ribosomes
- pili; no pili
- plasmids; no plasmids
- no mitochondria; mitochondria
- cell wall; only in plants and fungi
Lable the following and describe how it carries out the functions of life.
Food vacuole- nutrition
Contractile Vacuole- homeostasis(fills up with H20 and expels it throught the membrane)
Nucleus- reproduction
Cytoplasm- metabolism
cilia- Response and movement towards the food
Cell Membrane- Excretion(controls exit of molecules)
What are the levels of organisation?
cell- tissue-organ-organ system-organism
Why are there emergent properties at each level?
Because there are interactions of component parts
Outline the differention of cells in a multicellular organism.
All cells in the body have the same DNA but each cell is differnt in the sense that different genes are expressed. They are expressed by transcription and translation and these carry out different functions. A group of specialised cells is called a tissue.
Describe the division of labour
Specialised cells carry out different functions an dhave different structure which is adapted to their function. THis happens because a different set of genes is expressed through transcription and translation
Describe the functions of life in a chlamydomonas cell
- Flagella- response towards food
- Contractile vacuole- homeostasis
- cell membrane- excretion
- Stigma(eye spot)- response detects light
- chloroplast- nutrition site of photosynthesis
- vacuole- nutrition
- cytoplasm- metabolism
- nucleus- reproduction
- pyrenoid starch grain- nutrition food storage
How do you go from cm to mm?
x10
How do you from mm to micrometer?
x1000
How do you go from micrometer to nanometer?
x1000
What are stem cells?
Unspecialised cells that dicide continuously by mitosis and can give rise to many differentiated cells
Describe how Stargardt’s disease can be treated by use of stem cells
- It is a progressive loss of vision due to degenaration of retinal cells(genetic disease)
- Embryonic stem cells are harvested and differentiated in the lab into retinal cells.
- Retinal cells injected into patient’s eye where they are established
- Vision restored
Describe how leukemia can be treated by stem cells
- Cancer of bone marrow
- HSCs (hematopoetic stem cells) are harvested from donor or patient
- chemotherapy to destroy cancer cells
- HSCs transplanted back to patient–> divide and differentiate to form WBCs
What are sources of stem cells?
Embryonic stem cells
Adult tissues
Umbilical cord
Describe the advantages and disadvantages of the use of adult tissues compared to embryonic stem cells.
Advantages:
- consent
- less likely to form a tumor
- If own, less chance of rejection
- less ethical issues/individual not killed
Disadvantages:
- Difficult to obtain
- Less potential
- Some tissues do not have stem cells
What can surface area to volume ratio do ?
Limit cell size
Explain how SA/Volume influences cell sizes
As cell increases in size, the ratio of surface area/volume decreases.
Cells divide when they reach a certain size
The rate at which materials are produced is reliant on volume
The rate at which materials enter or leave a cell depends on the surface area
What is spontaneous generation?
Fomation of organsims from non living matter
DISPROVED BY PASTEUR
What is genetic code?
It is almost entirely a universal common fundamental biochemistry
How did the origin of the first cell happen?
- Synthesis of simple organic molecules from inorganic- Miller and Urey experiment
- Assembly of simple organic molecules into polymers- sea vents
- Self replicating molecule that can store genetic information- RNA
- Enclosure of the self- replicating molecule in a membrane- spontaneous assembly of lipids into a bilayer when placed in H2O
What does endosymbotic theory ecplain?
The origin of mitochondria and chlropolsats which were once free living prokaryote
Describe the endosymbiotic theory
An anaerobic prokaryote englufed an aerobic prokaryote. It was engulfed but not digested becasue the relationship was mutually beneficial and so it became the mitochondrion.
What is the evidence that supports the endosymbiotic theory?
- 70S ribosomes
- Circular, Naked DNA
- Double membrane- as a result of engulfement
- Mitochondria divide by binary fission
- Similar size to prokaryotes
What is the function of the membrane?
It controls the flow of substances in an dout of a cell and separates the cell from surroundings.
What is the membrane made out of?
Lipids(mainly phopholipids; animals also cholestrol)
Proteins
Draw a phospholipid and label it.
What does amphipathic mean?
It has both hydrophilic and hydrophobic parts
Which parts are hydrophobic and hydrophilic in a phospholipid and what are their other names?
Hydrophilic- Phosphate head
Hydrophobic- Hydrocarbon tail
Hydrophilic- polar
Hydrophobic- non-polar
What makes the membrane very stable?
Attraction between heads- H20 and between the tails
Draw a phopholipid with a cholestrol
What is the role of the cholestrol?
- Affects membrane fluidity
- Reduces permeability to some solutes
- Helps membranes to curve
List all the proteins found in the membrane
Integral- entirely integral/transmembrane
Peripheral
Channels
Glycoproteins
What can determine the localisation of proteins?
The amino acid sequence. Non polar AA casue proteisn to become embedded. Polar AA cause proteins to be peripheral a channel to be formed for hydrophilic substance to diffuse and an integral to protrude.
What are functions of membrane proteins?
- Receptors (hormones or neurotransmitters)
- Immobilized enzymes
- Channels
- Pumps
- Electron transport
- Cell to cell adhesion
- Cell to cell communication
Draw the Singer Nicolson Fluid Mosaic Model. FULLY LABELLED AND INDICATION OF HYDROPHOBIC AN DHYDROPHILIC PARTS IS NEEDED.
LOOK INTO NOTES FOR FURTHER DETAIL
What is the width of the membrane?
10nm
Draw the Davson- Danielli Model
Evidence of the Davson-Danielli Model.
Organic solvents penetrate facter than H2O–> non polar regions
Chemical analysis–> proteins and lipids
Amount of phopholipids in RBCs—> phopholipid bilayer
EM–> 2 dark lines separated by a lighter band (they thouhgt dark lines are the proteins light band the bilayer)
What did the singer nicolson model convey?
Proteins occupy a varitey of postions
Components move
What was evidence for the singer- nicolson model?
- Freeze fracture EM: proteins inside the bilayer
- Parts of the surface of membrane proteins are hydrophobic
- fusion of cells with labelled proteisn(different colour) therefore colours mixed–> proteins move.
What are organelles?
Discrete structures within cells that carry a specific function.
How do prokaryortic cells divide?
By binary fission
Which structures of double membranes?
Nucleus
Mitochondria
Chloroplasts
What do cell walls do?
Protects teh cell from bursting, maintains the cell’s shape
What does the cytoplasm do?
Site of cehmical reactions
What does the nucleoid do?
Region containing the bacterial DNA, which is a single, naked circular chrmosome
What do ribosomes do?
Site of protein syntehesis
What are plasmids?
Small circcular DNA in the cytoplasm
What does the flagellum do?
Rotates to move the cell
What does the rough endoplasmic reticulum do?
Synthesises proteins that will go to the cell membrane and will be secreted from the cell.
What does the Golgi apparatus do?
Proteins from teh RER arrive to the Golgi body in vesicles and are modified here. The proteins are then packaged into vesicles and are transported to teh membrane.
What do vesicles do?
Transport molecules inside the cell
What does the nucleus do?
Contains teh DNA and controls cell activitites, transcription takes place in the nucleus.
What is the nucleolus?
Inside the nucleus- site of robosomal RNA synthesis
What does the mitochondria do?
The reactions of aerobic respiration taje place in order to produce ATP which is the energy of the cell.
What is the smooth endoplasmic reticulum?
Synthesises lipids adn steroid hormones
What are lysosomes?
Contain hydrolytic enzymes for intracellular digestion. Break down engulfed organisms, organelles, macromolecules.
What are centrioles?
Cylindrical cell structures that form the anchor point o fmicrotubules. An associated pair of centrioles makes up the centrosome.
What is the following and how could you identify it?
EXOCRINE GLAND CELL OF PANCREAS
nucleus adn membrane bound organelles so cell is eukaryotic
No cell wall so animal cell
Extensive rer and vesicles as the cell syntehsises many proteins and treansports them for secretion
Many mitochondria as teh cell needs a lot of ATP for transport and protein syntesis
What is the following and how could you identify it?
nucleus and membrane- bound organelles so the cell is eukaryotic
cell wall, chloroplasts so a plant cell
many chloroplasts as it is a photosynthesising cell
What are the functions of life?
Metabolism
Response
Homeostasis
Growth
Reproduction
Excretion
Nutrition
What is metabolism?
All the chemical reactions occuring in an organism
What is response?
Ability to sense internal and external environment and respond
What is homeostasis?
Maintenance of internal environment within tolerable limits
What is growth?
A permanent increase in size and dry mass by cell growth and/or cell division
What is reproduction?
Production of new members of the same kind
What is excretion?
Gettign rid of waste products of metabolism
What is nutrition?
obtaining chemicals required for respiration and growth
How do you focus a light microscope?
- Place the slide on the stage centred below the objective lens
- Focus by moving the objective lens and specimen apart/ towards each other
- First use the coarse lens to find the area of interest then use the fine focusing knob
- First use a low magnification objective lens to find the area of interest. Then use a higher power.
- Adjust light intensity
What was the experiment of Louis Pasteur?
- Broth for palced in swan- necked flasks
- Curved necks allow the entry of air but prevent the entry of microorganisms
- Broth boiled to kill microorganisms
- In flask, no clouding so no bacterial growth
- After the necks were snapped, teh boiled broth became cloudy meaning bacteria grew
- This is beacuse bacteria from the air contaminated the broth
What is the basis of all membranes?
phospholipid bilayer
What are integral transmembrane?
They span the whole membrane width
Which organelle has no membrane?
Ribosome
What is this?
Rough endoplasmic reticulum
What is this?
Golgi apparatus
What is this?
Nucleus
What is this?
Chloroplast
What is this?
Lysosome
What is this?
Mitochondria
What are the methods of transport?
Diffusion
Facilitated Diffusion
Osmosis
Active transport
using vesicles
What is the difference between active and passive transport?
Active transport requires energy from ATP while passive transport does not need energy
What is diffusion?
The passive net movement of particles from a region of their higher concentration to a region of their lower concentration, as a result of their random motion
How do particles move in simple diffusion?
Across membranes, particles move down the concentration gradient and pass between phospholipids. Thus the membrane must be permeable to the particle.
What rapidly diffuses across a membrane?
The smaller and the more hydrophobic/non polar.
Which molecules/atoms CANNOT diffuse across a mebrane?
Large proteins
Charged molecules or atoms/ions
(Small uncharged polar molecules diffuse more slowly eg water)
What is the difference between facilitated and simple diffusion?
The transported molecules do not pass through the phopholipid bilayer but are transported by channel proteins
What do channel proteins enable in facilitated diffusion?
Enable substances to cross the membrane without interacting with the hydrophobic interior.
Which substances diffuse through facilitated diffusion?
Polar and charged molecules such as carbohydrates, amino acids and ions
What are channel proteins in facilitated diffusion?
They are specific for a substance. Voltage- gated sodium and potassium channels of neuronal axons.
What is active transport?
The movement of particles through the cell membrane against the concentration gradient which requires energy, ATP from hydrolysis which is carried out by protein pumps.
How do protein pumps work?
The particle enters the pump and binds
The pump changes conformation using energy from ATP
The particle is released at the opposite site of the membrane
The pump returns to its original conformation
What is a solvent?
Liquid that dissolves a substance
What is a solute?
Substance that is dissolved in a solvent
What is a solution?
Solute+ Solvent
What is osmosis?
The passive net movement of water molecules from a region of lower solute concentration to a region of higher solute concentration through a partially permeable membrane.
Where do water molecules pass through?
The phospholipid bilayer
What is osmolarity?
The concentration of osmotically active solutes in the solution (unit =osmole)
What is isotonic?
If the solution has the same solute concentration as the tissue
What is hypertonic?
If the solution has a higher solute concentration than the tissue. Net movement is out of the tissue
What is hypotonic?
If the solution has a lower solute concentration than the tissue. The net movement of water of from the solution into the tissue
What is the effect of animal cells in osmosis?
An animal cell is placed in a hypotonic solution, water enters by osmosis and it will swell up eventually and burst
If an animal cell is placed in a hypertonic solution water leaves the cell by osmosis and the cytoplasm shrinks and so the cell becomes crenated.
What is normal saline used for?
To introduce medicine is a patient’s blood, frozen to the consistency of slush for the transport of organs for transplantation, to rinse wounds
What is the effect of plant cells in osmosis?
If a plant cell is placed in a hypotonic solution, water enters the cell by osmosis and the cell becomes turgid. The vacuole fills with water and exerts pressure against the cell wall.
If a plant cell is placed in a slightly hypertonic solution, it loses some water by osmosis and becomes flaccid
If a plant cell is placed in a hypertonic solution it loses water and becomes plasmolysed
What is bulk transport?
The movement of macromolecules and large particles in and out of the cell using vesicles. Two types: Endocytosis, exocytosis
What allows materials to be taken into the cells by endocytosis and exocytosis?
The fluidity of the membrane;the cholesterol that it has
Describe the process of endocytosis.
The cells take up macromolecules.
Plasma membrane invaginates and encloses the material to be ingested
The membrane pinches off to form a vesicle
The inside of the plasma membrane becomes the outside of the vesicle membrane.
The membrane seals back on itself
What are the two main types of endocytosis?
- phagocytosis(ingestion of large particles)
- pinocytosis( ingestion of fluid and solutes)
Describe the action of exocytosis
Material is carried to the plasma membrane by vesicles and is secreted
Vesicles fuse with the membrane to release their contents
when the vesicle contents are expelled, the membrane flattens out again.
What are examples of exocytosis?
Secretion of hormones by endocrine gland cells, the release of neurotransmitters by neurones, secretion of digestive enzymes by pancreatic exocrine gland cell
Describe the process of vesicle transport within cells
Proteins and other non-protein material are transported within the cell in vesicles
Secreted proteins and integral membrane proteins are synthesised in the ribosomes of the rER and packed into vesicles
The vesicles bud off the rER and move to the Golgi apparatus
Vesicles fuse with the membrane of the Golgi apparatus
Proteins are being processed as they move through the Golgi apparatus
They are packaged again into vesicles which bud off the Golgi apparatus and are carried to the cell membrane
The vesicles fuse with the membrane and release their contents outside the cell
What are two examples of transport in axons?
Voltage-gated potassium channels used for facilitated diffusion
Na+/K+ ATPase is a pump performing active transport
What are the detailed steps of the Na+/K+ ATPase?
The pump is open to the inside of the axon, three Na+ ions enter and bind
ATP transfers one phosphate group to the pump which causes a conformational change to the pump
The pump opens to the outside and the three Na+ ions are released
Two K+ ions enter the pump and bind
Binding of the K+ ions causes the release of the phosphate group and thus a conformational change in the pump
Two pumps open to the inside and the two K+ ions are released. Cycle starts again.
What happens at the potassium K+ channels?
At resting potential, potassium channels are closed. They open for a short time in response to depolarisation. When potassium channels open they allow K+ ions to diffuse out of the cell, thus repolarising the axon. The channel rapidly closes. This happens by a globular subunit that blocks the channel pore. The globular subunit is attached by a flexible chain, fits inside the pore and remains there until the channel returns to its original closed state.
What are the three types of cell division?
Binary fission
Mitosis
Meiosis
What happens in binary fission?
DNA replication cell growth and elongation
DNA pulled to opposite poles and new membrane forms
Cell splits.
What is the cell cycle?
The sequence of events between two cell divisions
What are the two main phases of the cell cycle?
Interphase - divided into G1, S, G2
Cell division- Mitosis and cytokinesis.
Describe interphase
- A very active phase in which the cell grows
- DNA replication takes place
- Transcription and translation takes place
- Cell increases number of organelles (if plant increases also chloroplasts; if animal also centrioles)
- It is the longest phase of cell cycle
- Subdivided into G1, S and G2
What happens at the G1 phase?
Most of the growth and metabolic activities mentioned in interphase happen during this phase EXCEPT for DNA replication
What happens at the S phase?
DNA replication takes place. The chromosomes are copies and for the sister chromatids which are identical, which remain attached at the centromere until they separate for mitosis.
What happens at G2 phase?
More cell growth and preparation for mitosis
What is visible during interphase?
the genetic material is visible as chromatin NOT individual chromosomes.
What is mitosis?
The division of the nucleus that forms two genetically identical nuclei.
Subdivided into 4 phases: Prophase, Metaphase, Anaphase and telophase
What happens in cytokinesis?
The division of the cytoplasm so that two cells are formed. It begins before mitosis has been completed.
How does the DNA fit in the nucleus?
It condenses- DNA is successively coiled into shorter higher order structures. Super coiling,
What happens in eukaryotic chromosomes?
The DNA is associated with histone proteins which helps with condensation to form nucleosomes
What is the most condensed state?
Chromosome
When does mitosis occur?
Embryonic development
Tissue repair
Growth
Asexual reproduction
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens in prophase?
Chromosomes become shorter adn fatter by supercoiling. Microtubules grow in cytoplasm to form a spindle shaped array that extends from the cell poles to the equator. Nucleolus breaks down. End of prophase, nuclear membrane breaks down.
What happens in metaphase?
Microtubules continue to grow and attach to the centromeres on each chromosome. The chromosomes align at the equator of the cell.
What happens in the anaphase?
The centromere divides and the spindle microtubule pull the sister chromatids, now chromosomes, to opposite poles. Mitosis produces genetically identica nuclei because identical chromosomes are pulled to opposite poles.
What happens in telophase?
Chromosomes have reached the poles. Nuclear membrane reforms. Spindle microtubules break down. Chromosomes decondense and nucleolus forms.
How does cytokinesis take place in animals?
A contractile ring forms under the membrane which pulls the membrane to the equator inwards forming a cleavage furrow. When the membrane meets in the centre of the cell, the cell pinches apart
How does cytokinesis take place in plants?
Vesicles derived from the Golgi apparatus fuse at the cell equator and form the cell plate. The cell plate grows until it merges with the cell walls at the periphery. New membrane and cell wall form, splitting the cell in two.
What are the differences between plant and animal cell mitosis?
- In interphase, animal cells increase centrioles- plants do not have. plant cells increase chloroplasts- animals do not have.
- In cytokinesis, plant cells have cell plates while animal cells have cleavage furrow
What is the mitotic index?
Mitotic index= Number of cells in nitosis/total number of cells
What do tumour tissues have?
High mitotic index because cancer cells divide more than normal cells.
What is a cyclin?
Proteins that control cell cycle progression
How do cyclins work?
Cyclins bind to enzymes called cyclin-dependent kinases(cdk) and activate them. Cdks activate other proteins by phosphorylating them. The phosphorylated proteins carry out specific functions. Levels of cyclins rise and fall.
What does cyclin d do?
Triggers cells to move from G0 to G1 and and from G1 to S
What does cycline E do?
Prepares the cell for DNA replication in S phase
What does cyclin A do?
Activated DNA replication during the S phase
What does cyclin B do?
Promotes the assembly of the mitotic spindle and other tasks in the cytoplasm to prepare for mitosis
What is the order of the cyclins?
D is throughout
E-A-B
What is a tumour?
A cell mass formed by uncontrolled cell division
What can primary tumours be?
Benign- tumour cells cannot invade nearby tissues or move to other parts
Malignant- Tumour cells can move to other parts of the body and form secondary tumours
What is metastasis?
Spreading of tumour cells
How do tumours occur?
Mutations in genes. DNA mutations are random changes in the base of the sequence of the genes. DNA mutations can occur because of errors during DNA replication or because of mutagens.
What are oncogenes?
Genes that might lead to cancer when mutated. They are usually involved in the control of cell cycle so their mutation can cause uncontrolled cell division.
What are mutagens?
Agents that increase the rate of mutations and therefore the risk of tumour formation.
Which correlation is there between cigarette smoking and death rate due to cancer?
Positive
What does it mean if you find a correlation?
IT DOES NOT PROVE A CAUSAL LINK.
