Flashcards in Life at the Cellular level Deck (30):
What is a cell and why are they small?
A cell is the basic unit of all life
Cells are small to:
- help with the efficiency of the cell's absorption and waste expulsion processes
- allows fast communication from the nucleus to other organelles
- the cell can be regulated while the conditions for diffusion are still ideal
- are easier to replicate and replace when damaged
Explain the major differences between prokaryotes and eukaryotes
– Lack Nuclear membrane
– No Mitochondria
– No membrane bound structures
– Human cells
– Multicellular animals and plants
– Nucleus with membrane
– Membrane bound structures
Describe cell differentiation and its role in cancer
Cellular differentiation is the process where a cell changes from one cell type to another. Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover.
In cancer cells:
- Divide with out any control, able to pass through various checkpoints in the cell cycle.
- Fail to coordinate with normal cells
- Fail to differentiate into specialized cells
- Displace and replace the normal cells if not stopped
Describe the structures found in all cells
Cells are divided into 2 compartments
- Cytoplasm - contains cytosol and organelles
Define the role of the nucleus
Nucleus contains DNA, Nucleoprotein and some RNA
Define the role of the nucleolus
The Nucleoli serve as sites for ribosomal RNA synthesis and ribosomal assembly.
Define the role of the endoplasmic reticulum
Interconnecting network of membranous tubules, vesicles and flattened sacs (cisternae)
• Rough ER (Studded appearance due to ribosomes)
• Smooth ER
Rough ER synthesises and secretes/packages proteins
Smooth ER is responsible for lipid biosynthesis, membrane synthesis and repair
Define the role of the ribosome
Protein factories of the cells
Minute cytoplasmic organelles with 2 subunits.
Define the role of the golgi apparatus
• Stack of flattened vesicles which package and process secretory proteins.
• Also synthesise complex polysaccharides
Define the role of the lysosome
• Membrane bound organelles
• Act as cellular stomachs
• Contain amorphous granular materials which are used to break down bacteria and debris.
Define the role of the peroxisome
Small membrane bound organelles
• Catalase – Regulates hydrogen peroxide conc.
• Oxidases – Involved in Beta-oxidation of long chain fatty acids
Define the role of the mitochondrion
Mobile, cigar shaped organelles
• Permeable outer membrane containing porin
• Folded inner membrane – Cristae
• Filled with amorphous matrix
• Needed for oxidation + Krebs Cycle
Define the role of the flagellum and cilia
Cilia and eukaryotic flagella are both made of microtubules
o Cilia—short, usually many present, move with stiff power stroke and flexible recovery stroke. For example, cilia line the bronchus to remove microbes and debris from the lungs.
o Flagella—longer, usually one or two present, movement is snakelike. E.g. enables motility in sperm.
Describe the structure and function of the plasma membrane
The cell membrane is made up of a phospholipid bilayer.
o They are Dynamic (constantly formed and maintained, or dismantled and metabolised depending on needs of cell.
o Very flexible due to fatty acids (may rupture if over stretched)
o Insulators (hydrophobic hydrocarbon tails)
• Selective barrier
• Detects chemical messengers and signalling molecules from surrounding cells or other organs
• Contains membrane proteins (some span the membrane, others are embedded in the membrane) e.g. integral or peripheral
Define the role and constituents of the cytoskeleton
This provides strength and support, while also allowing for cell motility.
o Microfilaments – Fine strands of actin ( G and F actin subunits also found in non-contractile cells). In small intestine, Microfilaments form Microvilli.
o Microtubules - Larger than microfilaments, can form cilia (9 pairs of microtubules)
Define the 10 major elements used to construct human biomolecules.
O, H, C, N, Na, Cl, K, Ca, S, P
State the importance of chemical functional groups and molecular configuration and conformation in determining biomolecular function
Functional groups can affect how the molecule acts around others. E.g. OH groups allow for H bonds and soulubility in water. S groups allow di-sulphide bridges.
Configuration – The fixed arrangement of atoms in a molecule eg. Cis/Trans
Conformation – The precise arrangement of atoms in a molecule (free rotation etc.)
List and give examples of the five kinds of chemical reaction occurring in living organisms.
1) Redox Reactions – Usually 2 electrons are gained or lost.
Eg. Glycolysis in muscles – Glucose -> Pyruvate -> Lactate
2) Making/breaking C-C bonds
Eg. Cleavage of Glucose in Glycolysis
3) Internal Rearrangements
Eg. Glucose-6-Phosphate -> Fructose-6-Phosphate in Glycolysis
4) Group Transfers
Eg. Transfer of phosphate groups in glycolysis
Eg. Formation and breaking of nucleic acids and proteins by condensation and hydrolysis reactions respectively.
Describe the general structures of nucleic acids
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are polymers of nucleotides linked in a chain through 3',5' phosphodiester bonds.
A nucloetide = base + sugar + phosphate
There are 2 kinds of base in nucleic acids
– Pyrimidines (flat, single rings) – CTU
– Purines (flat, double rings) – AG
Briefly describe life processes in terms of the Laws of Thermodynamics.
Energy can be converted from one form to another, but not created or destroyed.
All energy transformations ultimately lead to more entropy in the universe.
This is true for living organisms, even though the processes create more order, the heat created is released into the universe, creating more entropy
Define metabolism, catabolism and anabolism, and describe, in outline, how they are interdependent.
Metabolism – The chemical processes in a living organism that allows food to be used for tissue growth. It is a mix of summative and degradative reactions (anabolism and catabolism respectively.)
Catabolism – Occur with -ve free energy, are spontaneous.
Anabolism- Occur with +ve free energy, are not spontaneous.
Energy obtained from catabolic reactions, is used up in anabolic reactions to produce more highly ordered compounds.
Describe, in general terms, the structures and contributions to metabolic flow of ATP, ADP, NADP, NAD, FAD.
ATP/ADP acts as a free energy carrier, coupling anabolic and catabolic reactions using phosphate group transfers.
NADP/NAD and FAD are used in redox reactions as electron carriers.
Define the general structures of polysaccharides
These are polymers of sugar monomers linked by glycosidic bonds (1-6 for straight, 1-4 for branches). Following all made from D-glucose:
Cellulose - very straight
Starch - branched
Glycogen - highly branched
Define the general structure of lipids
Usually contain one or more long-chain fatty acid, which can either be saturated or non-saturated (ratios determine viscosity)
There are several classes of lipids, including:
• Storage lipids, “fat”
• 3 fatty acid chains linked to glycerol
• Similar to triglycerides,
• Have ‘head’ group attached to glycerol
Describe different types of stem cells
Multipoint - Cells that can differentiate into many cell types
Pluripotent - can differentiate into all cell types of the body
Totipotent - can make cells found in all the body, plus embryonic or placental cells.
Inner cell mass of blastocysts is also a source of embryonic stem cells. The blastocyst is a structure formed in the early development of mammal
Programmed cell death
Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, chromosomal DNA fragmentation, and global mRNA decay.
Describe 6 plasma membrane functions
Site for receptors
Attach to cytoskeleton and ECM
Describe endocytosis and exocytosis
Endocytosis is a form of active transport in which a cell transports molecules (such as proteins) into the cell. Endocytosis and its counterpart, exocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane by passive means.
Exocytosis is a form of active transport in which a cell transports molecules (such as proteins) out of the cell
Describe some cell adhesion molecules and their functions
Tight junctions - create a physical barrier to diffusion across layers of cells, seals gaps between cells to make an impermeable barrier
Gap junctions - channels linking the cytoplasm of two cells together to allow cell communication or signal transduction e.g. connexins
Adhesive junctions – includes adherens junctions, desimsomes and hemidesmisomes, which transmit stress through tethering to cytoskeleton are cell–cell or cell–matrix. Adherens junctions are defined as a cell junction where the cytoplasmic face is linked to the actin cytoskeleton