Cells Flashcards
Functions of life carried by unicellular organisms (6)
Metabolism Response Homeostasis Growth Reproduction Nutrition
Outline the cell theory
- Living things are made of cells
- Cells are the smallest units of life
- Cells come from pre-existing cells
Explain the importance of the surface area to volume ratio
Surface area = rate at which materials enter of leave a cell
Volume = rate a t which materials are used or produced
–> too large cells aren’t able to take essential materials and excrete wastes / loose heat quickly enough
Explain emergent properties
The whole organism is more than the sum of its parts because of complex interactions between cells (in multicellular organisms)
What’s differentiation of a cell?
Specialization of a cell - some of the genes are being activated and expressed and determine how a cell would develop
! Once a pathway of development has begun, it is usually fixed
Why cells differentiate?
Cells need different genes to develop in different ways;
each cell has a full set of genes but expresses only those it needs to follow a certain pathway of development
Stem cells (2)
1) have the capacity to self-renew by cell division - can divide and replicate
2) can differentiate along different pathways (but once committed to a given pathway, a cell can only differentiate accordingly)
Outline the therapeutic use of stem cells
Stem cells can be derived from embryos or from the placenta / umbilical cord
This process requires:
- Chemicals to trigger differentiation
- Surgical implantation into patient’s tissue
- Suppression of immune system to prevent rejection
- Monitoring new cells to ensure they don’t become cancerous
1) embryonic stem cells may successfully be implanted in patients to treat Alzheimer’s, Parkinson’s or Type I diabetes
2) Grafting new skin cells in burns victims
3) Replacing nerve cells in spinal injuries
4) people with cystic fibrosis may be treated with their own stem cells, removed and genetically engineered with the cystic fibrosis gene; when planted back, these could lead to a formation of healthy cells lining the airways of their lungs
In general if stem cells are implemented the risk of tissue rejection is eliminated
Parts of E. coli bacterium (9)
1) PILI - attachment to surfaces and other bacteria
2) FLAGELLA - movement
3) CELL WALL - protects from rupture caused by osmosis and harm by other bacteria
4) PLASMA MEMBRANE - a barrier across which all nutrients and wastes must pass
5) NUCLEOID - genetic material; single circular chromosome
6) RIBOSOME - site of protein synthesis
7) FOOD GARNULE
8) MESOSOME
9) PLASMID
How do prokaryotic cells differentiate?
By binary fission
Parts of liver cell (7)
1) ROUGH ENDOPLASMIC RETICULUM - synthesis of proteins that will be exported from the cell
2) RIBOSOME - synthesis of proteins that will remain in the cell
3) GOLGI APPARATUS - site of synthesis of chemicals required by the cell; packaged into vesicles
4) LYSOSOMES - membrane-bound vesicles, contain enzymes
5) MITOCHONDRION - carries out aerobic respiration
6) NUCLEUS - controls and directs activities of a cell, stores genetic material (strands of DNA associated with protein, stored inside a double nuclear membrane)
7) PLASMA MEMBRANE
State three differences between plant and animal cells
- Cell wall
Plant cells have a cell wall (cellulose)
Animal cells do not have a cell wall - Chloroplasts
Plant cells may have chloroplasts
Animal cells do not have chloroplasts - Large, central vacuoles
Plant cells have a large, central vacuole
Animal cells have small, temporary vacuoles (if any) - Glucose storage
Plant cells store glucose as starch
Animal cells store glucose as glycogen
Extracellular components and their roles
1) Plant cell wall
- Provides support and mechanical strength (holds the plant against gravity)
- Maintains shape
- Provides a barrier against infection
2) Animal Extracellular matrix
- Formed by glycoproteins secreted by animal cells
- Provides support and anchorage for cells
- Segregates tissues from one another
Explain how phospholipid properties help to maintain membrane structure
Structure of Phospholipids:
- polar head (hydrophilic) made of phosphate and glycerol
- non-polar tail (hydrophobic) made of two fatty acid chains
Arrangement in Membrane:
Phospholipids spontaneously arrange in a bilayer
Hydrophobic tail regions face inwards (shielded from fluid)
Hydrophilic head regions face outwards towards the surrounding fluids
Structural Properties of Membrane
- Bilayer held together by hydrophobic interactions (weak associations)
- Weak associations allow for membrane fluidity / flexibility
- Fluidity allows membrane to break and reform (exocytosis / endocytosis)
- Hydrophilic / hydrophobic layers restrict entry of certain substances
Functions of membrane proteins (6)
Transport: Protein channels for active transport and pumps for passive transport
Receptors: Hormone recognition sites
Cell adhesion(przyczepność): Cytoskeletal attachments
Cell recognition: MHC proteins / Cell-to cell communication
Intercellular joining: Tight junctions
Enzymatic activity: Metabolic reactions
Diffusion
Passive movement of particles from a region of higher concentration to a region of lower concentration, (along the gradient);
Can occur only across membranes which are permeable to the particle and only if there’s a concentration gradient
Osmosis
Passive movement of WATER MOLECULES from a region of lower solute concentration to a region of higher solute concentration across a PARTIALLY PERMEABLE membrane
Simple diffusion
PASSIVE TRANSPORT - do not require ATP
Small or non-polar (lipophilic) molecules can freely diffuse across the membrane
1) the plasma membrane must be fully permeable to the solute
2) the pores in the membrane must be large enough for a solute to pass through
Facilitated diffusion
PASSIVE TRANSPORT
Large or polar / charged substances cannot freely cross the membrane
They require the assistance of transport proteins (carrier proteins or channels) to passively diffuse across the membrane
A substance that is otherwise unable to diffuse across the plasma membrane does so as a result of its effect on particular molecules present in the membrane;
In the presence of that substance, globular membrane proteins form into pores large enough to allow diffusion (they close up again when the substance is no longer present)
Active transport
Movement of substances across membranes using energy from ATP
can be against concentration gradient
uses protein pumps
each pump only transports specific substances so cell can control what’s absorbed and what’s expelled
Pumps work in a specific direction: the substance can only enter the pump on one side and exit only on the other
Bulk transport
Movement of vesicles by process generally known as cytosis
Endocytosis = uptake
Exocytosis = export
Phagocytosis = uptake of large particles
Explain transport between rough endoplasmic reticulum and Golgi apparatus
- Proteins are synthesized by ribosomes and enter rER
- Vesicles bud off from rER and carry proteins to Golgi apparatus
- Golgi apparatus modifies proteins
- Vesicles bud off from the Golgi apparatus and carry modified proteins to the plasma membrane
Interphase
- the longest phase (90% of life)
- chromosomes (DNA) replicate in prep for cell division
- number of mitochondria and/or chloroplasts increases
G1 - first phase of growth
S - synthesis of DNA
G2 - second phase of growth
Phases of mitosis
PMAT + cytokinesis
