Basic Biology Flashcards
Enzymology, Cell Organelles, Membrane Structures and Components, Biomolecules, Nutrients and Vitamins, Meiosis, Cell Proliferation and Mitosis, Cell Specification.
What is metabolism and what is the purpose of it?
Chemical reactions that occur in a living organism. The purpose is to produce energy, biosynthesis and excretion.
Define anabolism.
Synthesis of larger molecules from smaller ones (requires energy).
Define catabolism.
Synthesis of smaller molecules from larger ones (releases energy).
What are the 5 types of electron carriers?
Flavoproteins (NADH/NAD+) Cytochromes (haeme in haemoglobin) Copper atoms in mitochondrial membrane Uniquinane/Co-enzyme Q Iron-sulfur proteins (Fe3+/Fe2+)
Purpose of ATP.
Used as an energy intermediate. Produces 7.3kJ of free energy when hydrolysed.
Purpose of Enzymes.
Biological catalysts.
6 Types of Enzymes.
Transferase Ligase Oxidoreductase Isomerase Hydrolase Lysases
Characteristics of Enzymes.
- Globular Proteins
- Control metabolic reactions rate
- Lower activation energy
- Not consumed (re-usable)
- Substrate specific
- Shape of active site determines substrate
Define substrate.
The reactant.
Define active site
Region where substrate binds + undergoes chemical reactions.
Define co-factor.
Inorganic ions (Ca2+) which may be charged during the reaction.
Define co-enzyme.
Organic non-protein molecule (NAD+) that are a subset of co-factors.
Define prosthetic group.
A co-factor permanently attached to an enzyme.
Define apoenzyme.
Enzyme with a co-factor removed (inactive catalytically).
Define haloenzyme.
Enzyme with co-factor attached.
Describe the Lock-and-Key model.
- Active site is rigid shape
- Substrate needs to be matching shape
- No change in the active site shape
Describe the Induced fit model.
- Active site is flexible
- Shape of enzyme, active site + substrate adjust (improves catalytically)
- Greater range of substrate specificity
How does temperature effect enzyme activity.
Increases until reach optimum temperature where the enzyme begins to denature causing a decrease in activity.
How does pH effect enzyme activity.
Enzymes need to be around optimum pH decreases otherwise -> Specific to each enzyme.
How does substrate concentration impact enzyme activity.
Maximum activity occurs when all enzymes are saturated so it will reach maximum reaction velocity.
How do competitive inhibitors effect enzyme activity.
They are a similar shape to substrate so they bind to the active site meaning substrate can no longer bind.
How do non-competitive inhibitors effect enzyme activity.
Different shape to substrate but bind to enzyme in a allosteric place which alters shape of the active site meaning substrate no longer complimentary.
Describe allosteric modulators.
Can be inhibitors or activators but are different shaped to the substrate and are involved in feedback inhibition (switches process off when not needed).
Importance of enzymes.
Can be:
- Diagnostic markers of diseases
- Biochemical estimations + detections
Characteristics of Prokaryotic Cells.
-> Bacteria and Archaea
- Single-celled with DNA being circular
- Lack organelles
- DNA in nucleiod, no separation
- Rigid cell walls
- Functional structures in cytoplasm
Have Pili or Fimbriae and some have flagella
Characteristics of Eukaryotic Cells.
- > Animals and Plants
- Single of multicellular
- Contain organelles - which are specialised for their function
- DNA organised into chromosomes in the nucleus
- Nucleus surrounded by cytoplasm
Types of Cytosol organelles.
Mitochondria, Endoplasmic Reticulum (ER), Golgi apparatus, Lysosomes, Peroxisomes
Types of Inclusions.
Lipid droplets, Glycogen granules, Ribosomes
Types of Protein Fibres.
Cytoskeleton, Centrioles, Cilia, Flagella
Describe Sub-Cellular Fractionation.
- Disruption of plasma membrane
- Ultracentrifugation
- Cell compartments separate based on size and density
- Further density-gradient centrifugation can separate individual components from each fraction.
Describe Cell Membrane.
Phospholipid bilayer Physical isolation Regulation of exchange Communication Structural support
Describe Cytoplasm.
Semi-fluid material surrounding organelles
Site of many cellular activities
Offers cell support
Medium for internal cellular transport
Describe Nucleus.
Cells control centre
Regulates all cellular activity
Contains DNA (hereditary information)
Consists of nucleoplasm bounded by nuclear envelope (Two membranes - Inner/Outer/Pores)
Nucleolus - Transcribes and assembles rRNA
Chromatin - DNA looped around histone proteins
Nuclear pores - Allows communication between nucleus and cytosol, Ions + small molecules pass freely, Allows cell to restrict DNA to nucles
Describe Endoplasmic Reticulum (ER).
A system of folded, interconnected membrane vesicles.
- Large flattened sac-like structures (cisternae)
- Internal space = Lumen
Describe Smooth ER.
No ribosomes
Biosynthetic + Biotransformational activities (Lipids/Steroids/Steroidal hormones) - in liver/kidney
Describe Rough ER.
Ribosomes on cytosolic side
Site of protein synthesis -> Protein transported to lumen for modification
Describe Golgi Apparatus.
Large sac-like membrane vesicles, associated vesicles + tubules
Processing station
- Package + distribute cell products (for internal/external use)
- Vesicles budding off ER travel and are accepted by Golgi
- Vesicles budding off Golgi travel to other organelles/cell surface
Describe Vesicles.
Similar membrane to plasma membrane
Internal conditions different to cytosolic environment
Describe Vacuoles.
Component for storage + transport (often temporarily)
Largest in plants
Describe Lysosomes.
Membrane bound vesicles used in intra/extracellular digestion of biomolecules + old cells.
Characteristics: 0.5-1um, Contain lysozymes, Lumen has low pH, Acid hydrolases (active at low pHs).
Special carbohydrate to prevent self-destruction
Larger amount in white blood cells
Describe Peroxisomes.
Membrane bound from ER
Characteristics: 0.1-1um, Contain oxidase + catalase, Detoxify + decompose harmful substances
Lots in the liver
Describe Vesicles Transport.
Move molecules in a cell
Recognise + fuse with target membranes
Describe Secretary Vesicles.
Contains materials to be excreted from the cell
- Removal of waste
- Release chemical signs (hormones)
Vesicle fusion (Full/Kiss-and-run - reusable)
Describe Mitochondria.
Site of aerobic respiration + energy production
Double membrane:
- Inner = Folded forming cristae
- Area within cristae = matrix
- Gap = Inter-membrane space
Membrane in inter-membrane space allow for cell death (apoptosis)
Distribution in cells + tissue depend on function (muscles = high)
Matrix - Contains enzymes, ribosomes, granules, DNA, machinery to form ATP
Describe Cytoskeleton.
3D structure that fills the cytoplasm Roles: - Cell Movement - Cytokinesis (cell division) - Organisation of organelles
Composed of:
- Microfilaments = 3-6nm, threadlike, mainly actin, carry out movement
- Microtubules = 20-25nm, cylindrical tubes, a + B tublin subunits, determine cell shape, used for flagella + cilia movement
- Intermediate filaments = 10nm, overlapping + twisted conformation, provide tensile strength, anchor organelle + nucleus, form junctions between cells + matrix
Describe the Structure of the Cell Membrane Lipids.
Most membrane lipids are amphipathic
Many are phospholipids (glycerophospholipids/sphingolipids)
Sterols have stabilising roles
Proteins are associated to surface/span membrane
Describe Glycerophospholipids.
Glycerol as polar head
Attached to a phosphate ion and an R-group
Helps to fine tune membrane properties
Describe the two types of Sphingolipids.
Sphingomyelin = Phosphocoline head group Glycosphingolipids = Mono/oligo-saccharide head group
Explain the Main Constituents of a Cell Membrane.
Phospholipids = Membrane formation Glycolipids = Antigen recognition Sterols = Membrane fluidity Proteins = Signalling
State the 7 types of Amphipathic Phospholipids.
Phosphatidylcholine (PC) Phosphatidylethanolamine (PE) Phosphatidylglycerol (PG) Phosphatidylinositol (PI) Phosphatidylserine (PS) Diphosphatidylglycerol (DPG) Sphingomyelin (SP) - Animals
State the 2 types of Gylcolipids.
Cerebrosides (mono)
Gangliosides (oligo - inc sialic acid -ve charged)
State the type of Sterol in Humans and its Properties.
Cholesterol
Properties
- Amphipathic
- Intercalates into bilayer
- Influences membrane fluidity + decrease ion permeability + small polar molecules
Describe the Phospholipid Bilayer.
Hydrophobic core stabilised by Van Der Waals forces
Hydrophilic head groups interact by ionic interaction
Movement between layers stabilised by flippases
Only functions in fluid state
Lateral diffusion is fast/Transverse is slow
At low temperatures it solidifies = gel phase
Explain the Factors that Affecting Membrane Fluidity.
Longer fatty acid chains - Reduce Fluidity
-> Increased Van Der Waals forces
Unsaturated fatty acid chains - Increased Fluidity
-> Chains no longer linear - Decreased forces - Desaturate enzymes re-tailor chain
Sterols in fluid - Decrease Fluidity
-> Restrict movement of compounds
Sterols in gel phase - Increase Fluidity
-> Facilitate movement of other membrane compounds
State the 3 Membrane Proteins.
Integral
Lipid-Anchored
Peripheral
Explain the Integral Membrane Proteins.
Amphipathic Span the membrane (integral polytopic) Partially embedded (integral monotopic)
Explain the Peripheral Membrane Proteins.
Lack hydrophobic regions
Do not interact with fatty acid ends of membrane lipids
Associated with membrane structure
- Electrostatic attraction
- Hydrogen bonding (to protein or polar head groups)
Explain the Lipid-Anchored Membrane Proteins.
Found in both membrane surfaces
- Protein located on membrane surface
Anchored via covalent bonds to lipid molecules within membrane
- Fatty-acid anchored membrane proteins
- Synthesised + attached to a lipid in membrane
Isoprenylated membrane proteins
- Synthesised + modified by addition of multiples of the isoprenylgroup
State the Functions of Membrane Proteins.
Transport ATP Production Biotransformations (metabolism) Receptors Cell-cell recognition
Explain Lipid Rafts.
Phospholipids + proteins distributed asymmetrically in membrane
- Highly organised membrane structures
- Thicker
- Rich in cholesterol and sphingomyelin
Accumulate molecules (ie transmembrane proteins, lipid-anchored proteins + glycoproteins)
State the Roles of the Cell Membrane.
Physical isolation Regulate exchange with environment Communication between cell + environment Structural support Cellular identification
Explain the 4 Transport Mechanisms.
Simple diffusion
- High -> Low conc. gradient
- Small + hydrophobic molecules (O2,CO2)
Osmosis
- Water diffusion High -> Low water potential
Facilitated Diffusion
- High -> Low conc. gradient
- Require transport protein
- Ions (K+,Na+), Monosaccharides, Amino Acids
Active Transport
- Low -> High conc. gradient
- Ions, Glucose, Amino Acids
- Requires energy (ATP, Electrochemical gradient)
State the Process that occur over a Mobile Membrane.
Endocytosis Exocytosis Pinocytosis Phagocytosis Receptor-Mediated Endocytosis Exocytosis
State the formula for Carbohydrates.
(CH2O)n
Describe the Functions of Carbohydrates.
Primary - Short-term immediate energy generation
Secondary - Immediate-term energy storage (glycogen)
Tertiary - Structural components (cellulose)
State the bond between Monosaccharides.
Glycosidic
State the Products Formed by Condensation Bonds between Monosaccharides.
Disaccharides (sucrose)
Oligosaccharides (ABO glycolipids)
Polysaccharides (cellulose)
Describe the difference between Alpha and Beta Glucose.
Alpha = OH bonds on same side on carbon 1 + 6 Beta = OH bonds on opposite sides on carbon 1 + 6
State the main Functions of Lipids.
Energy Storage
Heat/Insulation
Structural components of cell membranes
Communication
Describe the Characteristics of Lipids.
Non-Polar
Not very soluble in water, Soluble in non-polar/weakly polar organic solvents
Saturated = Single C-C bonds, linear appearance, solid at RTP
Unsaturated = 1+ C=C bond, C=C gives distinct bend, reduces melting point liquid at RTP
Carboxyl Head - Non-polar + Hydrophilic
Fatty Acid Chain - Hydrophobic
Describe Triglycerides.
Glycerol + 3 Fatty Acid Chains
Stored as cytoplasmic ‘lipid droplets’
Main storage for energy: Long term + high in energy
Describe Phospholipids.
Glycerol + 2 Fatty Acid Chains + Phosphorylated Alcohol
Describe Eicosenoids.
Consists of: Prostaglandins (PG’s), Thromaxones (TX’s), Prostacyclins (PGI’s), Leukstrienes (LT’s)
Derived from arachidonic acid
Describe Isoprenoids - Steroids.
Built around 4-ringed hydrocarbon skeleton
Cholesterol is the base of all steroid hormones
- Glucocorticoids
- Mineralocorticoids
- Androgens
- Oestrogens
- Progesterones
Describe Isoprenoids - Sterols.
Cholesterol
- Mammalian cell membranes
- Precursor of steroid hormones + bile salts
Ergosterol
- Cell membrane component in fungi
Phytosterol
- Plant sterol (suggested cholesterol-lowering effect)
State the Roles of Proteins.
Enzymes Structural Motility Regulatory Transport Hormone Receptor Defensive Storage
State the Structure of Amino Acids.
NH2CHRCOOH
State the 4 Groups of Amino Acids.
Group I - Non-Polar
Group II - Polar
Group III - Acidic
Group IV - Basic
State the Name of the Bond between Amino Acids.
Peptide bonds formed from condensation reactions.
Forms an N-C-C backbone
Describe the 4 Polypeptide Structures.
Primary: Amino acid sequence
Secondary: H-bonds between polypeptide backbone at regular intervals forms a-helix (coils) and b-sheets (folds)
Tertiary: Interaction between R-groups + backbone from ionic, disulphide bridges and H-bonds
Quaternary: Interaction between 2+ polypeptide chains (Haemoglobin has 4)
Explain the Function of Nucleotides.
Allow living organisms to pass information to future generations and carries metabolic energy.
State the 2 types of Nucleotides.
Purines - Adenine + Guanine
Pyramidines - Thymine, Cytosine + Uracil
Describe Deoxyribose nucleoties (DNA).
Four nucleotides: A + T, C + G
Sugar = D-deoxyribose
Describe Ribose nucleotides (RNA).
Four nucleotides: A + U, C + G
Sugar = D-ribose
Explain the DNA Double Helix.
Base pairing between two complementary strands (5’ to 3’ vs 3’ to 5’ strands) which forms right handed helix with a sugar phosphate backbone.
Describe Meiosis in simple terms.
Gametes (haploid cells) fuse which allows organisms to reproduce, creating genetically different offspring to their parents.
Describe the 2 types of Reproduction.
Sexual
- Combination of haploid sex cells (gametes)
- Fertilisation forms zygote
- Change in genetic information so genetic differences
- Restores diploid number from gamete fusion
Asexual
- Via Mitosis ONLY
- Genetically identical offspring
State all the Stages Involved in Meiosis.
DNA Replication Meiosis I Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II
Describe Meiosis I.
Duplicated maternal + paternal homologous chromosomes pair up alongside each other
-> Genetic recombination
Line up at equator of meiotic spindle
Homologous are pulled apart and separated into 2 daughter cells.
Describe Prophase I - Meiosis.
Chromosomes duplicated
Chromosomes condense + become visible
Synapsis + crossing over occurs
-> Increases genetic variation
Describe Metaphase I - Meiosis.
Homologous chromosomes align at the metaphase plate
Centromeres of homologous chromosomes are oriented towards opposite poles.
Describe Anaphase I - Meiosis.
Mircotubules attaches to the kinetochores shorten
Homologous chromosomes move to opposite cell poles
Centromeres don’t break (chromatids don’t separate).
Describe Telophase I - Meiosis.
Spindle fibres disintegrate and cytokinesis occurs
Each daughter cell has half the number of chromosomes.
Explain the Importance of Genetic Variations.
Generates haploid cells genetically different from each other
Produces individuals with novel genetic combinations
- Can survive + reproduce in variable environments
- Removes harmful mutations from a population.
Explain Proliferation.
The physical process of cell division Main Type in Eukaryotes = Mitosis Increases somatic cell number Occurs in most tissues Critical in maintaining homeostasis Begins in embryogenesis continues throughout lifespan
Describe the different Proliferate Abilities.
Unable to:
Cardiac myocytes, Neurones
Can resume proliferation from G0:
Skin fibroblasts, Smooth muscles cells, Epithelial cells of internal organs
Continual proliferation:
Blood cells, Skin epithelial cells
Describe the Regulation of Cell Proliferation.
Environment - Nutrients, Temperature, pH, O2
Positive/Negative - Cell adhesion, Growth factors
Intracellular - p53, Cytochrome C, Bcl proteins
Describe Mitosis in simple terms.
The copy of an existing cell to produce genetically identical cells usually for growth and repair.
Describe the Stages involved in Mitosis.
S-Phase: DNA Synthesis
M-Phase: Nuclear division (mitosis) + Cytokinesis
G1 Phase: Gap phase 1
S-Phase: Period of cell growth + proteins and organelles doubled
G2 Phase: Gap phase 2
M-Phase: Cell divides into two
Explain the Importance of Gap Phases in Mitosis.
To grow and monitor internal + external conditions.
Describe G1 Phase - Mitosis.
Takes approx. 9.5 hours
Ensures:
Cell large enough to enter S-Phase
Describe G2 Phase - Mitosis.
Takes approx. 2.5 hours Ensures: Cell completely replicated Replication errors corrected Cell large enough to divide
Explain how Mitosis is Regulated.
Information from: Cell cycle events (nutrients, cell-density, growth factors)
External environment: Cyclins, Cyclin-dependent kinases (CDK)
Regulatory proteins bind to CDKs causing phosphorylation and activation
Describe S Phase - Mitosis.
Chromosomes replicate
New DNA synthesised -> Duplicate chromosome constructed
Chromosome visible during division
After replication:
Each chromosome forms 2 identical chromatids
Chromatids joined at the centromere
State the Stages of M-Phase - Mitosis.
Prophase Prometaphase Metaphase Anaphase Telophase + Cytokinesis
Describe Prophase - Mitosis.
Chromosomes condense
- Nuclear membrane and nucleoli disappear
Outside nucleus
- Mitotic spindle begins to form (centromeres, aster + microtubules)
- Centromeres move away from each other
Describe Prometaphase - Mitosis.
Nuclear envelope forms
Microtubules attach to the chromatids at the kinetochores
Describe Metaphase - Mitosis.
Centromeres are at opposite poles
Chromosomes line up at the metaphase pole
All chromosomes are attached to each of the pole
Describe Anaphase - Mitosis.
Connection between chromatids at the centromeres is cleaved
- Each chromatid is now a daughter chromosome
Chromosomes are pulled to opposite poles as cell elongates
Describe Telophase + Cytokinesis - Mitosis.
Two daughter cell nuclei form - Nuclear envelope forms, cytoplasm divides Chromosomes become less dense Contractile ring assembles - Actin + Myosin filaments - Cytoplasms divided in 2
State the Importance of Mitosis.
Regulates development
- Maintains size, morphology + organ function
- Involved in ageing, oncogenesis + regenerative medicine
Describe the effect of Abnormal Proliferation.
Uncontrolled cell division/death which is the cause of most metastasis -> cancer
Describe Cell Specialisation/Differentiation.
Cell changes from one type to another
Usually results in a more specialised cell type
Determines role of the cell
State the main types of Stem Cells.
Embryonic stem cells
Adult stem cells
Induced pluripotent stem cells
Describe Embryonic Stem Cells (Blastocysts).
Isolated from the inner cell mass of blastocysts
Can differentiate into all specialised cell types
Division results in ‘self-renewal’
Totipotent and Pluripotent
Describe Adult Stem Cells (Bone Marrow).
Found in various tissues
- Obtained after birth
- Large number in umbilical cord blood + bone marrow
Act as repair systems
Progenitor cells
- Make cells to renew cells (maintains cells)
- Divided into 2 different cells (precursor + progenitor)
Describe Induced Pluripotent Stem Cells (iPSC).
Lab generated - Reprogrammed differentiated adult cells
Used for research
Self-renewing (like embryonic stem cells)
State and Describe the Potents of Stem Cells.
Totipotent - Any cell type
Pluripotent - Any cell type, except placenta
Multipotent - Limited cell differentiation types
Oligopotent - Few cell differentiation types
Unipotent - One cell differentiation type
Progenitor cell - Decedents of stem cells that can further differentiate
Describe Blood Cells.
Formed in bone marrow from multipoint haematopeoietic stem cells
Erythrocytes (Red blood cells)
Leukocytes (White blood cells)
Platelets
Describe Neurones (Cells).
Self-renewing multipoint stem cells
-> Located in subventricular zone + hippocampus
Purpose: Transmit information, oldest + longest cells, lack centrioles
Astrocytes
Oligoadendrocytes
Describe Sperm Cells.
Purpose: Form organelles Spermatogenesis - Haploid spermatozoa develop from germ cells in seminiferous tubules - Totipotent stem cells Specialisations: - Head (acrosome - enzyme + nucleus) - Tail (undulipodium - movement) - Small + thin
Describe Tissues.
Organised communities of cells
Work together to carry out specific tissues
Role determined by cell types
Categories: Connective, Epithelial, Muscle, Nervous
Describe Epithelial Tissues.
Found: - Outer layer of skin - Lining of body cavities - Blood + lymph vessels Protects exposed + internal surfaces from abrasion, dehydration + destruction
Describe Connective Tissues.
Cells + extracellular matrix (ECM)
Function: Protection, Support + Integration
Connective tissue proper, Loose + Dense irregular
Dense regular, Adipose tissue, Cartilage, Blood, Bone + Haemapoietic tissue
Describe Muscle Tissues.
Contract + Produce movement
Skeletal (voluntary) muscle
Smooth muscle (involuntary)
Cardiac muscle -> heart (involuntary)
Describe Nervous Tissues.
Specialised for propagation of electrical signals
98% of tissue in brain + spinal cord
Functions: Sensory input, Integration, Control of muscles, Glands, Homeostasis + Mental activity
Describe an Organ.
Collection of tissues joined in a structural unit for a common function
Made of many tissue + several cell types
Example: Heart
Describe an Organ System.
Group of organs that work together as a biological system to perform one or more function.
