bio

Flashcards covering stem cell properties, potency levels, embryonic development, gene expression, stem cell niches, and induced pluripotency based on lecture notes.

Stem cell

An unspecialized cell capable of self-renewal through division and differentiation into specialized cell types.

Three main phases of the stem cell life cycle

1. Quiescence: Resting phase with no division or differentiation.\n2. Self-renewal: Dividing to produce more stem cells.\n3. Differentiation: Becoming a specialized cell type.

Main factor limiting stem cell proliferation

Telomere shortening. Repeated divisions cause chromosome telomere caps to shorten until the cell can no longer divide.

Four levels of cell potency in order of highest to lowest flexibility

1. Totipotent: Can form any cell type.\n2. Pluripotent: Can form almost any cell type.\n3. Multipotent: Can form a small range of related cell types.\n4. Unipotent: Can form only one cell type.

Progression of cell potency during embryonic development

Starts as totipotent (zygote/morula), transitions to pluripotent (inner cell mass of blastocyst), and ends as multipotent or unipotent specialized tissues.

Why fully differentiated tissues are not classified as stem cells

They are fully specialized cells that lack potency and the capacity for self-renewal.

Emergent properties

New functions or capabilities that arise from the interactions of individual cells working together in a multicellular organism.

Advantages of cell specialization in multicellular organisms

Allows cells to perform specific tasks more efficiently, save energy, and develop adapted structures and metabolic pathways.

Single nucleotide polymorphism (SNP)

A single-base variation in the DNA sequence among individuals of the same species.

Mechanism allowing cells with identical genomes to differentiate

Differential gene expression, where specific genes are selectively turned on or off in different cell types.

Differential gene expression in muscle, skin, and nerve cells

Cells share the same DNA but express unique combinations of specific genes to carry out distinct functions.

Central dogma of gene expression

The pathway of genetic information flow: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$.

Housekeeping genes

Genes expressed in almost all cells because they code for fundamental functions necessary for cellular survival.

Three variables controlling differential gene expression

Intensity (expression level), timing, and location (signal exposure).

Key stages of early embryonic development in order

Zygote $\rightarrow$ Cleavage $\rightarrow$ Blastula $\rightarrow$ Gastrula.

Stem cell niche

The local microenvironment that sends signals regulating whether a stem cell stays quiescent, self-renews, or differentiates.

Somatic stem cells

Multipotent adult stem cells in body tissues that divide to replace damaged or lost cells.

Epidermal stem cell niche location and function

Located in the bulge of hair follicles; maintains stem cells responsible for skin and hair regeneration.

Hematopoiesis

The production of blood cells and platelets from multipotent stem cells inside the bone marrow niche.

Induced pluripotent stem cells (iPSCs)

Adult somatic cells reprogrammed to behave like embryonic stem cells, avoiding ethical issues related to embryo destruction.

Effect of chemical signal gradients on embryonic gene expression

Varying signal concentrations across the embryo turn specific genes on in high-signal areas and keep them off in low-signal areas.

Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass but not others

Plasma (cell) Membrane

Protective layer external to the cell membrane, consists of cellulose in plants and chitin in fungus.  Protects the cell from bursting under turgor pressure.

Cell wall

Flattened sacs of membrane with attached ribosomes that synthesize proteins.  The proteins are packaged into transport vesicles.

Rough endoplasmic reticulum

Contains most of the DNA that control the eukaryotic cell.  Contains the nucleolus (where ribosomes are made) and chromatin (uncoiled chromosomes).

Nucleus

Site of photosynthesis; produce glucose using light energy, CO2 and H2O

Chloroplast

Consists of flattened membranMembrane bound sacs, larger than vesicles, stores water and dissolved nutrients.ous sacs; receives transport vesicles from the ER, modifies proteins made in the rER and produces secretory vesicles

Golgi apparatus

Membrane bound sacs, larger than vesicles, stores water and dissolved nutrients.

Vacuole

Sacs of digestive enzymes used to digest food and old, worn out cell parts.

Lysosome

Site of protein synthesis; suspended in the cytosol or attached to the rER.

Ribosomes

Site of aerobic cellular respiration, producing ATP from glucose.

Mitochondria

Small sac used to carry proteins made on the rER to the Golgi.

Transport vesicle

Proteins found outside an animal cell that function in support and adhesion so that the cells can connect together to form a tissue.

Extracellular matrix

Flattened sacs of membrane without attached ribosomes.  Synthesizes lipids and buds off to form transport vesicles.

Smooth Endoplasmic reticulum

Small sac used to carry proteins from the Golgi to the cell membrane for secretion.

Secretory vesicle

Whip-like structures used for cell locomotion or to create a current next to the cell.

Cilia and Flagella

classifications

domain, kingdom, phylum, class, order, family, genus, species

Carries accessory genes such as antibiotic resistance

plasmids

mr mr heng

metabolism, reproduction, movement, response, homeostasis, excretion, nutrition, growth

the science and practice of classifying and categorizing things or concepts based on shared characteristics.

taxonomy

Understand how to make and stain temporary mounts of cells and tissues.

• Put specimen on a clean mount and place a drop of water on it

• View under microscope

cell theory

• all cells must come from preexisting cells

• cells are the basic unit of life

• all living things are composed of one or more cells

eyepiece graticule

a measurement on the eyepiece to help create an increment of the cell

stage micrometer

the ruler found on the slide that helps create actual measurements out of the graticule

actual size

image size / magnification

image size

use your ruler and measure length of drawing

magnification

image size / actual size

A vesicle fuses with the cell membrane and releases its contents outside

exocytosis

endocytosis

The cell takes in large molecules (bulk) by using their cell membranes to wrap around them

tyoes of endocytosis

• phagocytosis

• pinocytosis

• receptor mediated endocytosis

isotonic

solute inside and outside are equal

hypertonic

more solute outside than inside cell

• cell loses water

bulk transport

Small molecules and water enter or leave the cell through the liquid bilayer or by transport proteins

hypotonic

more solute inside the cell

• cell gains water

net diffusion

• Only some particles go through, some come back out 

• Random movement of molecules

diffusion

particles moving from high concentration to low concentration

structures that are common in all living organisms

plasma membrane, DNA, cytoplasm, ribosomes

applications of electron microscopy

• study cell structures

• looking at detailed structure of cells

• examining organelles

• proving membrane structure

• identifying specific organelles

• medical and disease research

prokaryotic cells

single celled organisms that lack a nucleus

eukaryotic cells

more complex than prokaryotic

• have membrane bound organelles

• have nucleus

Chemical reaction happens within teh cell to release / use energy

Metabolism

• Dividing into 2 cells 

• Binary fission

Reproduction

Uses pseudopodia to move

Movement

Recognizing and reacting to environment

Response

Controls the amount of water inside cells

Homeostasis

• Removing waste products 

Excretion

• Surrounds and takes in food particles 

• Nutrition 

Uses nutrients to grow larger

Growth

red blood cells - atypical cell structure

• lacks nucleus

• lacks mitochondria

striated muscles

• have many nucleus for one membrane

  • exceptionally long

phloem tubes

• no ribosomes

• no nucleus

• no end cell walls

• no mitochondria

• Amphipathic lipid has hydrophilic head and hydrphobic tails 

• Head faces water, tails face away, tails face other tails

Describe the formation of sheet-like bilayers in water by amphipathic lipids.

passive transport

• simple diffusion

• osmosis

  • movement of water through phospholipid bilayer

• facilitated diffusion

  • diffusion through proteins

Explain the reasons behind the selective permeability of the lipid bilayer.

• The middle section between the tails are hydrophobic 

• Prevents charged polar water soluble substances from passing 

  • Only lets small uncharged particles and water are allowed 

the movement of molecules by diffusion across the lipid bilayer.

Small or non polar molecules can pass through the lipid bilayer unassisted

integral proteins

found within the hydrophobic centre

• some make it to the membrane

  • 
    

peripheral protein

bound to teh inner or outer surface of the membrane

aquaporins in transporting water

• specific protein that only allows water to enter

• found in osmosis and facilitated diffusion

  • 
    

why diffusion happens across a membrane

• Random movement 

  • Particles are always in constant movement 

• Differences in concentration 

  • High concentration to low concentration 

• Membrane permeability 

  • Membrane may allow certain particles through

structure and role of channel proteins

• Transmembrane proteins that form a channel for ions or polar molecules to exit and enter 

• Allow specific molecules to move from high -> low concentration 

• A form of facilitated diffusion -> no ATP required

importance of pump proteins in active transport

• Proteins that transfer substances against their concentration gradient 

• Move from low -> high concentration 

• Require ATP 

• Help the cell maintain different concentrations of substances inside and outside the cell

role of facilitated diffusion in the selective permeable membrane

• Uses carrier or channel proteins in the membrane  

• Because it uses certain proteins that only allows certain substances through it creates a semi permeable membrane

role of active transport in the selective permeable membrane

• Uses pump proteins 

  • Allows certain cells to choose what enters and exits from low to high gradient

glycoproteins

• Carbohydrates linked to proteins 

• Found on cell membrane 

• Helps with cell recognition and cell to cell communication 

• Act as receptors for signals

  • 
    

Glycolipids

• Carbohydrates linked to lipids 

• Contribute to membrane stability by forming hydrogen bonds with water around the cell 

• Found on the outer surface of the cell 

• Helps with cell recognition and cell-to-cell communication

know all of these

what are organelles

• Structures within a cell that perform specific function

3 organelles and their function

• Mitochondria 

  • Produces energy 

• Ribosomes 

  • Makes protein 

• Nucleus 

  • Contains DNA

  • Controls the cell 

• Explain the advantages, using phagocytic vacuoles and lysosomes as examples, of the compartmentalisation of cytoplasm.

• Prevents interference 

• Faster and more efficient reaction 

  • Allows waste to break down safely

lysosomes - compartmentalisation

• Contain digestive enzymes 

• Fuse with phagocytic vacuole  and release enzymes to break down particles

phagocytic vacuoles

• occurs when cells engukf large particles

• keeps the particles in their own compartments

  • 
    

advantages of separating cytoplasm and nucleus

• DNA stays protected while mRNA carries instructions to ribosomes 

• Allows cytoplasm to send signals to the nucleus 

• allows the post-transcriptional changes to occur before translations - eukaryotic only

cell specialization - development

• egg just specialized

• zygote

• morula

• blastocyst

• embryo

how one fertilized egg can develop into many different types of cells.

• Fertilisation -> zygote 

• Zygote divides -> many unspecialized cells

• All cells have same DNA 

• Different concentrations turn genes on and off 

• Causes specialization into different types of cells 

Outline the properties of stem cells and their different capabilities to become different cell types

• Stem cells -> unspecialized 

• Can divide into many stem cells 

• Can differentiate into any type of cell

pluripotent

• Can become almost any type of cell 

• Ex: embryonic stem cells 

totipotent

• Can become any type of cell 

• Including extra embryonic tissue 

• ex: zygotes

multipotent

• Can become a limited type of cells 

unipotent

• Very limited 

what is stem cell niche

The environment a cell is exposed to that influences the diffrentiation

• gives signals to replenish needed cells