Cells Flashcards
According to cell theory…
- Living organisms are composed of cells
- The cell is the smallest unit of life
- Cells can arise from pre-existing cells
What are the exceptions to cell theory?
- fungal hyphae- continuous cytoplasm
- muscle cells- multinucleated
- algae cells - unicellular organisms that are large
What are the 7 functions of life?
- metabolism
- homeostasis
- excretion
- growth
- nutrition
- reproduction
- sensitivity
What is the cell’s volume?
the rate of metabolism is a function of cell’s mass
What is the cell’s surface area?
The rate of material exchange is the function of the cell’s surface area.
What is the relationship between the volume and surface area of the cell?
As a cell grows the volume (units3), it increases faster than the surface area (units3)
- if the metabolic requirements exceed the material exchange the cell will die
- cell must stay small or increase the SA:Vol ratio to survive
What is the formula for magnification (MIA)?
Magnification= Image Size / Actual Size
What is the formula for the Actual Size (AIM)?
Actual Size = Imagine Size / Magnification
Remember 1000um = 1 mm
What are the emergent properties?
Function that is present in multicellular organisms, but not present in its individual component cell. They arise from the interactions between individual cells to produce new functions.
Difference between the light and electron microscopes
- light microscopes have lower magnification and can view living specimens in natural colors
- electron microscopes can only view dead specimens in monochrome and have higher magnification
What are stem cells?
The unspecialized cells that have two qualities:
- self renewal- they can continously divide and replicate
- potency- they have capacity to differentiate
2 types of stem cells and explain them
- Adult stem cells - multipotent, meaning they can differentiate into a limited range of cell types specific to the tissue or organ in which they are found.
- Embryonic stem cells -pluripotent, meaning they have the potential to differentiate into any cell type in the body.
Explain totipotent cells
can form any cell type as well as the extra-embryonic tissue
Explain pluripotent cells
can form any cell type e.g. embryonic stem cells
Multipotent cells
can differentiate into closely related cell types
Unipotent
cannot differentiate but are capable of self-renewal
Describe the stem cell therapy
This therapy can replace damaged or diseased cells with healthy ones. The therapeutic use of stem cells involves:
- harvesting stem cells from appropriate sources
- triggering cell differentiation
- monitoring new cells to ensure they do not become cancerous
- implanting new cells
Explain the stem therapy of the Stargardt’s disease
Replacing defective retinal cells
Explain the stem therapy of the Parkinson’s disease
Replacing damaging nerve cells
Explain the stem therapy of the Leukemia disease
Replacement of bone marrow
State the definition of cell differentiation
It means that each cell contains the entire set of genetic instructions for certain organism. Differentiation involves the expression of some genes. The activation of different genes within a given cell will cause it to develop differently from other cells.
Describe the stem cell from the embryo
- growth potential: high
- tumour risk: high
- disadvantages: requires the destruction of the embryo
Describe the stem cell from the umbilical cord blood
- growth potential: low
- tumour risk: low
- disadvantages: cells must be stored from birth at cost
Describe the stem cell from the adult tissue
- growth potential: low
- tumour risk: low
- disadvantages: may be restriction in availability
Gene packaging
The process where the DNA is packaged within proteins as chromatin in the nuclei of eukaryotic cells.
- active genes are loosely packed as euchromatin
- inactive genes are packed tight as heterochromatin
The cell wall in the plant cells
- contain the cell wall that is made up of cellulose -> it supports the cell and limits its volume
What the plant cell consists of?
- smooth ER
- rough ER
- nucleus
- mitochondrion
- vacuole
- chloroplast
- ribosomes
- cell wall
- membrane
- cytoplasm
- golgi body
The function of chloroplast
it contains chlorophyll which is a site for photosynthesis and this process occurs in leaves
What is the chloroplast made of?
- DNA
- rybosomes
- outer and inner membranes
- thylakoid
- granum(the whole sac o thylakoids)
- stroma
Structure of mitochondria
structures bounded by the a double membrane. The inner membrane of these forms cristae. The fluid inside mitochondria is called matrix. It contains DNA, ribosomes, proton pumps and ATP synthase.
Function of mitochondria
- produce ATP by cell respiration, site of aerobic respiration
Explain the ER
Comprises a network of tubes and flattened sacs. It is continuous with the plasma membrane and nuclear membrane. The types of ER are:
- smooth- without ribosomes
- rough - with ribosomes
Function of smooth ER
- transporting materials between organelles and synthesis of metabolism
Function of rough ER
- transporting materials between organelles and synthesis of proteins
What is the function of Golgi apparatus?
- storing and modifying proteins for specific functions and prepares them for transport to other parts of the cell
Structure of Golgi apparatus?
- transport vehicles
- secretory vehicles - transporting hormones
- lumen - inner space
- cisternae - outer space
Lysosomes (only animal cells)
Membrane bound organelles that contain the digestive enzymes
What are perixisomes?
self-replicating organelles containing oxidative enzymes
Rybosomes
small molecules that do not have any membrane. their function is to synthesize proteins. site of translation.
What is the structure of ribosomes?
- small subunit
- large subunit
- proteins + rRNA
Where are 70s and 80s ribosomes?
- 70S in prokaryotic cells, mitochondria and chloroplasts
- 80S in the cytoplasm of eukaryotic cells
Centriosome (only animal cells)
cellular structure involved in the process of cell division ( meiosis and mitosis ) and it contains the set of microtubules.
Structure of animal cells
- lyzosome
- ribosomes
- mitochondrion
- nucleus
- ER
- vacuole
- golgi apparatus
- cytoplasm
- membrane
Function of nucleus
It stores genetic information and it is the site of transcription
Structure of nucleus
It contains the nuclear membrane, nuclear pores, nucleolus, and chromatin.
What are the differences between the animal cells and plant cells?
- animal cells do not have chloroplasts, cell wall, no plasmodesmata
- animal cells have temporary vacuoles but plant cells have large central vacuole
- cholesterol present in the animal cells
- animal cells have glycogen and plant cells have starch
Plasmodesmata function (only plant cells)
They connect the cytoplasm of neighboring cells causing an exchange of materials.
Double membrane is called also
nuclear envelope
Structure of prokaryotic cells
- fimbriae (sex pilli)
- plasmids
- cytoplasm
- cell wall
- capsule
- cell membrane
- flagellum
- ribosomes
- circular chromosome (DNA)
Function of pilus
used for bacterial conjugation
Function of fimbriae
used for attachement not movement
Function of plasmids
exchanged via sex pilli in conjugation
Function of flagella
used for locomotion
What is bacterial cell wall composed of?
carbohydrate molecule called peptidoglican
Difference between fimbriae and flagella
flagella is used for locomotion and fimbriae is used for attachement. fimbriae are shorter and thinner than flagella.
What is the binary fission?
Asexual reproduction by a separation of the body into two new bodies. The cross wall separates the parent and daughter cell into two identical cells.
Explain the process of binary fission
- cell elongation occurs and the chromosome is duplicated
- the cell wall and cell membrane begin to grow inwards forming a cross wall
- the ingrowing cell walls meet and two identical cells are formed (cytokinesis)
State the definition of conjugation
Conjugation is the process by which one bacterium transfers genetic material to another through direct contact. During conjugation, one bacterium serves as the donor of the genetic material, and the other serves as the recipient.
Steps of conjugation
- donor cell attaches to a recipient cell with its pilus. The pilus draws cells together
- The cells contact one another (connect)
- One strand of plasmid DNA transfers to the recipient
- The recipient synthesizes a complementary strand, restoring its complete plasmid
Phospholipid bilayer
- it contains a hydrophilic head composed of phosphate
- contains two hydrophobic tails, each composed of fatty acid chain
- phospholypids are amphipathic
What is the meaning of amphipathic properties?
The structure has hydrophilic and hydrophobic parts
How is the phospholipid bilayer held together?
by weak hydrophobic interactions between the tails
What makes the membrane flexible and fluid?
that individual phospholipids can move within the bilayer
What amphipathic properties do?
restrict passage of certain substances -> semi-permeability
What is the width of the bilayer?
4nm
Two molecules that reduce membrane fluidity
cholesterol and proteins
Major force that causes the formation of the membrane bilayer
hydrophobic interactions
What is cholesterol?
Fundamental component of animal cell membranes.
Function of cholesterol
reduces membrane fluidity and permeability to some solutes and anchors peripheral proteins.
What is the function of membrane proteins?
- cell recognition
- signal transduction
- attachment
- transportation
- enzymatic functions
Difference between the peripheral proteins and integral proteins
- integral show amphipathic character with hydrophobic and hydrophilic and they are permanently embedded in the plasma membrane
- peripheral proteins are found temporarily attached to the mitochondrial membrane
Fluid Mosaic Model
Explains that cells contain fluid - membrane components that can move position and mosaic- phospholipid bilayer that is embedded with protein
Davson- Danielli Model
Explains that phospholipid bilayer lies between two layers of protein (sandwich model). It was discarded because : this model could not explain the transport mechanism of substances across the plasma membrane.
what is the glycoprotein?
a molecule that contains carbohydrates and proteins
What properties do cell membranes have?
- semi-permeable (only certain things can cross)
- regulation of the material passage
types of membrane transport can either be:
- passive - along the concentration gradient, no ATP requirement
- active - against the concentration gradient, ATP is required
Types of passive transport
- simple diffusion
- facilitated diffusion
Simple diffusion - explain
the net movement of particles from a region from higher concentration gradient to a region of lower concentration until the equilibrium is reached. Involves small molecules
Facilitated diffusion - explain
the passive movement of molecules across the cell membrane via the aid of a membrane protein (channel protein or protein carrier). Involves large molecules
Osmosis
The net movement of water molecules across a semi-permeable membrane from a region of low solute concentration to a region of higher solute concentration.
What is osmolarity?
measure of solute concentration
Types of solutions
hypertonic, hypotonic, isotonic
Describe hypertonic solution
high solute concentration - gains water
Describe isotonic solution
same solute concentration
Describe hypotonic solution
low solute concentration - loses water
Describe active transport
uses ATP to move the molecules against the concentration gradient. Molecules bind to a protein pump and hydrolysis of ATP causes a confomational change, translocating the molecule across the membrane.
Types of active-passive transport (co-transport)
- symport : both molecules move the same direction
- antiport : molecules move in opposite directions
Vesicular transport
Cellular transport via membranous vesicles in cells thanks to the fluidity of plasma membrane.
Types of vesicular transport
- exocytosis - materials released from cell via vesicles
- endocytosis - materials internalised within a vehicle
Abiogenesis
the formation of living cells from non-living materials.
Explain the abiogenesis process
- non-living synthesis of simple organic molecules
- assembly of organic molecules into complex polymers
- formation of polymers that can self-replicate
- packaging molecules into membranes to form a cell
Law of biogenesis-Louis Pasteur experiment
Experiment demonstrated by Louis Pasteur. It consisted of boiled broth in flasks with S-shaped necks. The broth was boiled after being poured into the flasks to destroy any living microorganisms that may have been present in the broth. The S-shaped necks prevented microorganisms from entering and contaminating the broth after boiling. It proved that there is no such life force in air, and organisms do not arise by spontaneous generation. Cells can only arise from pre-existing cells.
Endosymbiosis theory
Eukaryotic cells are believed to have evolved from aerobic prokaryotes that were engulfed by endocytosis. Evidences that chloroplasts and mitochondria arised via endosymbiosis:
- double membranes
- 70s ribosomes
- DNA is naked and circular
- fission-like division
Paramecium
contains:
- nuclei
- food vacuole: contains ingested food
- contractile vacuole: regulates water balance
- cilia: hair-like structures
- oral groove: forms food vacuoles
Why Paramecium is particularly mobile?
it helps them to feed on water organisms
What is the property that is necessary for emergent properties to occur?
cells or tissues interact to function as a unit
What causes the formation of cancer?
- oncogenes
- mutagens
- proto-oncogens
What are cyclins?
Proteins that control progression of the cell cycle.
How cyclins work?
- they bind to cyclin dependent kinases CDKs
- the activated complex phosphorylates proteins involved in specific cell cycle events
- after the event occured, the cyclin is degraded and the cyclin dependent kinase is rendered active
Function of cyclins
Cyclins regulate the cell cycle by binding to and activating cyclin-dependent kinases (CDKs), controlling progression through cell cycle phases, regulating mitosis, and monitoring cell cycle checkpoints.
What is metastis?
Spread of cancer from an original site to a new body location (forming a secondary tumor).
Tumors
the resulting abnormal cell growths. they might remain in their original location (benign) or spread and invade the neighboring tissues (malignant).
What causes cancers?
- Mutagens are agents that change the genetic material of cells:
- can be physical (UV), chemical, and biological in origin (viruses) - Genetics:
- proto-oncogenes stimulate cell growth
- tumor suppressor genes repress cell cycle progression
What are the two mechanisms of cell death:
- necrosis (cell homicide) - the cell loses the functional control due to injury and the cell bursts and then releases its contents (inflammation).
- apoptosis (cell suicide) - controlled event triggered by mitochondrial proteins, the cell fragments are recycled.
What are two sources of stem cells commonly used in therapeutic treatments?
- Embryonic Stem Cells
- Pluripotent Stem Cells
How mitotic index can be used in the diagnosis of cancer?
The mitotic index helps doctors identify how quickly cancer cells are dividing, which can indicate how aggressive the cancer is.
Definition and formula of mitotic index
Measure of proliferative status of a cell population - type of prognostic tool. Formula:
- cells that undergo mitosis/ all cells x 100%
Explain the cell cycle
The cell cycle is an ordered set of events that culminates in cell division. It includes the interphase and M phase
Interphase
an active phase of the cell cycle where many metabolic reactions occur and it consists of G1, G2, and S stages.
What processes occur in interphase?
- DNA replication
- Cell growth
- Transcription and translation
- Respiration
M phase
The period of a cell cycle in which the cell and contents divide. It is the division of diploid nucleus into two identical diploid nuclei. It includes:
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
What is supercoiling?
Chromatin condense via supercoiling to become tightly packed chromosomes. Due to replication, chromosomes consist of identical sister chromatids (joined at centromere).
What is chiazma?
an intersection or crossing of two traits in the form of the letter X
What is chiazmata?
X-shaped structure of paired chromatids visible in the prophase
What is the function of mitosis?
tissue repair, organism growth, asexual reproduction
Cytokinesis process
Cytoplasm division where a cell splits in two. It occurs with telophase and differs in plants and animals
What is the difference between cytokinesis in animals and in plants?
plants: microtubules form a ring and contract towards the centre (centripetal)
animals: vesicles form at the cell centre and fuse outwards to form cell plate (centrifugal)
What happens in the prophase?
- DNA supercoils and condenses (forms visible chromosomes)
- the nuclear membrane dissolves
- centrosomes move to poles and begin to produce spindle fibers
What happens in the metaphase?
- spindle fibers attach to centromere of each chromosome
- spindle fibers contract and move the chromosomes towards the cell centre
- chromosomes form a line along the middle of the cell
What happens in the anaphase?
- spindle fibers continue to contract
- sister chromatids separate and move to the opposite sites of the cell
- sister chromatids are regarded as two separate chromosomes
What happens in the telophase?
- chromosomes decondense - DNA forms chromatin
- nuclear membranes form around the two identical chromosomes sets
What happens in the cytokinesis?
- cytoplasmis division occurs to divide the cell into two daughter cells
- each of the daughter cell contains one copy of identical sister chromatid
- daughter cells are genetically identical
Primary tumour
original site of a cancerous growth of cells
What allows the cell cycle to continue dividing?
high levels of cyclins
What are the parts of chromosome?
- kinetochore
- chromatid
- centromere
If a cell that has 20 chromosomes undergoes mitosis, then what will be created?
two daughter cells will be created and each will have 20 chromosomes
When spindle forms?
prophase
Compared to X chromosome, the Y chromosome is…
much smaller
What can be determined from karyotypes?
the number of chromosomes present
What occurs during mitosis in plant cells
condensation of chromosomes
4 types of potency of stem cells
- totipotent
- pluripotent
- multipotent
- unipotent
