Life at a Cellular Level 1 Flashcards
What is a cell?
Functional unit of all living things
Describe a prokaryotic cell.
- Bacteria
- Lack nuclear membrane
- No mitochondria
- No membrane bound structures
Describe a eukaryotic cell
- Human cells
- Multicellular animals and plants
- Nucleus with membrane
- Membrane bound structures
What are stem cells?
- Multipotent: Cells that can differentiates into many cells
- Pluripotent: Cells that can differentiate into all cell types of the body
What are changes in gene expression reflected in?
The alteration of cell structure and behaviour
What process can some cells go through during differentiation?
Cell fusion
What are cancer cells?
- Cells that divide without any control and fail to coordinate with normal cells.
- Fail to differentiate into specialised cells
- Displace and replace the normal cells
What is apoptosis?
- A process of programmed cell death
- A central mechanism controlling multicellular development
What are tissues?
Functional arrangements of cells
What are organs?
Mixture of different tissues
What are systems?
Cells or organs with similar functional roles
What is the cell membrane?
-Selective barrier
What does the plasma membrane detect?
Chemical messengers and signalling molecules from surrounding cells or other organs
How can membrane lipids be described.
Amphipathic
-Hydrophilic head and hydrophobic tail
What are the functions of the plasma membrane?
- Transport
- Surface of enzymatic activity
- Receptors for signal transduction
- Intercellular joining
- Cell-cell recognition
- Attachment to cytoskeleton and ECM
Describe passive diffusion.
- Concentration gradient needed
- Lipid-soluble molecules pass freely (non-polar)
Describe facilitated diffusion
- Concentration gradient needed
- Requires carrier molecules
What do tight junctions do?
Seals gap between epithelial cells
What do adheren junctions do?
- Connects actin filament bundle in one cell with that in the next cell
- Link actin filaments in two different cells
What do desmosomes do?
- Connect intermediate filaments in one cell to those in the next cell
- Link keratin filaments in two different cells
What do gap junctions do?
- Allows the passage of small water soluble molecules from cell to cell
- Links two cells cytoplasm together
Where would you find tight junctions?
- Intestine
- Kidney
- Blood brain barrier
What are tight junctions dependent on?
Calcium
Where would you find gap junctions?
- Heart muscle
- Liver
- Pancreas
What are gap junctions composed of?
Connexions (6 subunit membrane spanning proteins)
What are the 4 types of cell signalling?
- Contact-dependent
- Paracrine (cell only signals local cells)
- Synaptic (specific to neurones)
- Endocrine (signal gets carried around body and has mass effect
What does fast cell signalling involve?
Adrenaline or nerves
What does slow cell signalling involve?
Genes being switched on/off
Describe the structure of a mitochondria?
- Porous outer membrane
- Inner membrane with cristae
- Matrix containing calcium binding sites and enzymes for oxidation of food molecules.
- Circular DNA
- Ribosomes
What does the nucleus contain?
- DNA
- Nucleoprotein
- RNA
What are nucleoli?
Sites of ribosomal RNA synthesis and ribosomal assembly
What 2 forms does DNA come in?
- Heterochromatin
- Euchromatin
Describe the nuclear membrane of the nucleus.
- Phospholipid bilayer
- Encloses the nucleus
- Contains pores
- Closely associated with the ER
Describe the ER.
- Membrane bound
- RER has ribosomes
What is the ER responsible for?
Protein modification and transport coordinated by the RER and Golgi body
What does the smooth ER do?
Mainly breaks down compounds such as drugs and glycogen or synthesises some compounds such as lipids
What are lysosomes used for?
- Used to separate enzymes from the rest of the cell
- Used in autophagy or digestion of engulfed particles.
What does the cytoskeleton do?
- Supports and maintains cell shape
- Holds organelles in position
- Moves organelles
- Involved in cytoplasmic streaming
- Interacts with extracellular structures to hold cell in place
What are the 3 different divisions to the cytoskeleton?
- Microfilaments
- Intermediate filaments
- Microtubules
What are microfilaments involved in?
Cell dynamics
What are intermediate filaments involved in?
Hold organelles in place
What are microtubules involved in??
Mitosis and meiosis
What are cilia and flagella made from?
Microtubules
What are cilia?
- Short
- Usually many present
- Move with stiff power stroke and flexible recovery stroke
What are flagella?
- Longer
- Usually one or two present
- Movement is snakelike
