Unit 2: Cells Flashcards
Name 2 differences between prokaryotes and eukaryotes.
Eukaryotes are larger than prokaryotes.
Eukaryotes contain a nucleus, prokaryotes have free strands of DNA.
Name 3 differences between plant and animal cells.
Plant cells have a permanent vacuole.
Plant cells have chloroplasts.
Plant cells have a cellulose cell wall.
What is the role of the nucleus?
Contains genetic information which controls the activities of the cell.
What does the nuclear envelope do? (Nucleus)
It connects the outer membrane to the Endoplasmic Reticulum.
What do nuclear pores do? (Nucleus)
They allow large molecules to enter the nucleus.
What is the nucleoplasm? (Nucleus)
The cytoplasm contained in the nucleus.
What are the chromatin? (Nucleus)
They are unwound, free chromosomes within the nucleus.
What does the nucleolus do? (Nucleus)
It creates ribosomes and ribonucleic acid (RNA).
What is the role of mitochondria?
Where aerobic respiration occurs.
What is the double membrane? (Mitochondria)
The outer layer controls what goes in and out of the mitochondria, and the inner layer is folded into the cristae.
What is the cristae? (Mitochondria)
An extension of the inner membrane to increase surface area.
What is the matrix? (Mitochondria)
Found between the cristae, where enzymes for respiration are contained.
What is the role of ribosomes?
They create proteins.
What are the subunits of a ribosome?
The large unit and the small unit, both containing RNA and protein.
What are the two types of ribosome?
80S and 70S
What is the role of the Rough Endoplasmic Reticulum?
For protein synthesis. Its’ folds process proteins and offer a pathway for the transport of materials throughout cells.
What is the RER made of?
Sheet-like membranes that spread out throughout the cytoplasm, providing a large surface area for ribosomes to attach to during protein synthesis.
What is the role of lysosomes?
Intracellular digestion of materials.
What is the role of centrioles?
Organisation of the spindle.
What is the role of the golgi apparatus?
It is involved with the modification of proteins. Also creates lysosomes.
What are microtubules and what is their role?
Fine, hollow structures composed of the protein tublulin. They contribute to the cykoskeleton and the centrioles, as well as making up the spindle.
What is the Fluid-Mosaic model?
The phospholipid bilayer has a mosaic pattern between each end of the phospholipid - they were also able to move about, resulting in the name Fluid-Mosaic.
What is the role of the cell wall?
Provides structure for plant cells.
What is the role of the cell surface membrane?
Regulates movement of substances in and out of the cell.
What is the role of microvilli?
Found on cells involved in processes such as absorption.
What is the role of a vescicle?
Transports substances in and out of a cell.
What is the role of a chloroplast?
The site where photosynthesis takes place, contains chlorophyll and absorbs light.
What is the definition of:
Diplococci
Streptococci
Sarcinae
Staphlococci
Pairs
Chains
Packets
Clusters
What are the key features of prokaryotes?
- blue green algae is photosynthetic
- DNA processes singular circular thread of DNA
- plasmids only carry few genes, antibiotic resistance, special metabolic pathways
- shapes = cocci, bacilli, spirilli
Importance of bacteria:
- decomposers in carbon cycle
- nitrogen fixing bacteria in nitrogen cycle
- pathogens (disease)
- gut flora help with digestion
What is viral replication?
A vines cannot reproduce itself, it weest invade a host cell and take over the cell activities, eventually causing destruction of the cell, and killing it.
What is the organisational hierarchy of a cell?
- Biological molecules
- Organelle
- Cell
- Tissue
- Organ
- Organ system
- Organism
Structure and function of the central vacuole.
- Any fluid filled space in a cell with a membrane
- Filled with cell sap (provides osmotic pressure).
- Animal cells may have temporary vacuoles.
- Important in controlling osmosis
- Used as a storage vessel
Structure of chloroplasts
They are large
Contain DNA and ribosomes
Surrounded by an outer membrane.
Membrane with a large sa.
Contain chlorophyll
Cell specialisation
Egg g+ sperm → zygote → mitotic division, day 5-6 turns into stem cells.
Embryonic stem cells are pluripotent.
On day 5-6, all cells are the same. The gene is switched on and will produce a protein and an enzyme to allow the cell to become specialised = gene expression.
Plasmids in prokaryotes notes
- help with antibiotic resistance
- they are molecules peoduced by pathogens that specifically influence a hosts function to allow the pathogen to thrive
- promote bacterial conjugation
What is the cytoplasm (protoplasm in prokaryotes)
- gel-like matrix of warer, enzymes, nutrients, wastes, gases and contains cell structures
-location of growth, metabolism and replication - a bacterias way of storing nutrients in granules
What is cellular scaffolding
- a backbone or skeleton for cells, within the cytoplasm
What is the prokaryotic cell wall made of
- murein, which is a huge polymer of interlocking chains of peptidoglycan monomers
Two major classes of bacteria
- gram positive, with 90% peptidoglycan in cell walls
- gram negative, with 5-20% peptidoglycan in cell walls
Three types of bacterial shape
- bacilli
- cocci
- spirilli
Four formations of bacteria
- pairs = diplococci
- chains = streptococci
- packets = sarcinae
- clusters = staphlococci
Central vacuole notes
- fluid filled space in a cell with a membrne
- cell sap, which provides osmotic pressure
- animal cells may have temporary vacuoles
- controls osmosis
- storage vessel
Cell wall of planta notes
- made of carbohydrate called cellulose, contains beta glucose
- thin middle lamellae between adjacent cell walls, cementing them together
- hydrogen bonds hold layers of cellulose together, as well as microfibrils
Plant cell wall functions
- support structure
- withstand turgor pressure
- transport of water
Root hair cell functions
- take up water vis osmosis
- takes up minerals and nutrients via active transport
Xylem vessel notes
- water drawn uo transpiration stream because of cohesive forces between molecules
- caspanian strip prevents movement of water across cell wall
- lignin strengthens cell walls of xylem
Virus notes
- don’t belong to a kingdom
- acellular, non-living
- infectious agent, made of nucleic acid in a capsid
- contain enzyme called reverse-transcriptase
Virus notes
- don’t belong to a kingdom
- acellular, non-living
- infectious agent, made of nucleic acid in a capsid
- contain enzyme called reverse-transcriptase
What is electron microscopy
- a high energy beam of electrons has a wavelength if about 0.004nm, allowing for high resolution, shot at dead sample to produce an image
What is cell fractionation
- process where cells are broken up and the different organelles are separated based on their size/mass using gravity
Three stages of cell fractionation
1) homogenising - blends up tissue to break open cell membranes
2) filtration - removes large debris, which would sink to the bottom of the test tube
3) ultracentrifugation - faster the tube is spun the more debris collected at the bottom, organelles are separated into pellets
What is a chromosome
- long thread of a molecule called DNA
What is a gene
- a short section of DNA on a chromosome that codes for a specific protein
What is a karyotype
- shows all of the sets of homologous chromosomes
Full process of cell division
1) cell growth - cell grows and increases number of sub-cellular structures
2) replication - genetic material is doubled, the DNA replicates and forms two copies of each chromosome
3) mitosis - genetic material is divided
Full cell cycle
G1 - cell returns to normal size, doubles organelles, cytoplasm increases, genes are switched on or off
S - replication occurs, new pairs of DNA are known as sister chromatids
G2 - cell synthesises proteins needed for division, ATP storage increases, microtubules assemble into spindle fibres
G0 - cell leaves cycle and quits dividing, reached end stage of development
Factors affecting cell division
- availability of nutrients
- external signalling molecules
- proof reading enzymes checking mutations
Stages of mitosis
Interphase - chromosomes are nor individually distinguishable, DNA replicates
Early prophase - centrioles move to opposite poles, spindle fibres form, chromosomes condense
Late prophase - nuclear envelope begins to disintegrate
Metaphase - chromosomes line up along equator of cell, spindle fibres attach at their centromeres
Anaphase - spindle fibres pull chromatids apart, and are separated
Telophase - chromosomes uncoil, nuclear membrane forms around each set, spindle fibres disintegrate
Cytokinesis - membrane constricts and divides, forming two identical daughter cells
Cell surface membrane functions
- control entry and exit of materials in organelles
- separate organelles from cytoplasm
- provides internal transportation system
- provide surfaces on which reactions can occur
Cell surface membrane structure
- bilayer of lipids along with proteins, intrinsic and extrinsic
- phospholipids make 75% of the surface
- glycolipids make 5% of surface
- cholesterol makes 20% of surface in animal cells, rarely found in plants
Intrinsic protein functions
- act as channels, maintaining gradient
- transport
- receptors, some proteins recognise and bind to target molecules
- enzymes, ATP
Extrinsic proteins
- serve in transport of molecules
- receptors
- hold to cell membranes by weak molecular attractions, like ionic or hydrogen bomnds
Biological catalysts notes
- lower activation energy
- proteins made up by different sequences of amino acids
Induced fit theory
Active site is majority specific to the substrate, however the active site changes shape to put pressure on the substrate to make or break bonds
Cofactors that help enzymes function
Coenzymes - organic molecules often containing a vitamin
Inorganic ions - e.g Fe+ in catalase
Prosthetic groups - e.g haemoglobin
4 functions of glycoproteins
1) act as channels by maintaining concentration gradient
2) receptors on cell surface
3) enzymes, e.g ATP transcriptase
4) transporters, e.g some are able to identify and attach to specific substances
Glycolipids notes
- on external surface of cell membrane
- carbohydrate section extends between cells, called a glycocalyx
- maintains flexibility of cell
- used as markers for cell recognition, acting as antigens
- help with cell adhesion
Role of cholesterol in surface membrane
- important component of cell membrane
- rarely found in plant cells
Degree of CSM fluidity determined by:
- length of fatty acid chains, longer = less fluid
- proportion of saturated fatty acids
- steroid content, higher = less fluid
Actin microfilaments notes
- found in eukaryotic cells
- serves basis of cytoskeleton
- gives strong mechanical support if bundled together
- allows materials to be transferred in cells
Hypertonic solution meaning
A solution of higher concentration of solute than inside the cell
Isotonic solution meaning
A solution of equal concentration to the cell
Hypotonic solution meaning
A solution of lower concentration of solute than inside the cell
Co-transport of glucose into bloodstream
1) sodium ions are pumped out of the epithelial cells into the ileum, creating a concentration gradient
2) causes sodium ions to diffuse from lumen back into epithelial cells, via sodium-glucose channel proteins. This gradient pulls glucose into the cell via the channel proteins.
3) glucose diffuses out of epithelial cell into the blood, by facilitated diffusion
Factors affecting active transport rate
- speed of individual carrier proteins
- number of carrier proteins
- rate of respiration in cell
- availability of ATP
What is an antigen
Molecules that can can generate an immune response when detected by the body
What are pathogens
- organisms that cause disease.
- all pathogens have antigens on their surface, which are recognised as foreign, and attacked by the immune system
What are abnormal body cells
Cancerous or pathogen infected cells, which trigger an immune response
What are toxins
- poisons, some of which are produced by bacteria.
- the immune system can respond to toxins, as well as the pathogens that release them
Four stages of immune response
1) phagocytosis
2) T-Cells
3) B-Cells
4) Antibody production
What is phagocytosis
- a phagocyte is a type of white blood cell that carries out photosynthesis
1) phagocyte recognises a foreign antigen
2) cytoplasm engulfs the pathogen
3) pathogen is contained inside a phagocytic vacuole
4) lysosome breaks down the pathogen
5) phagocyte presents the antigens, activating other immune cells
What are T-cells and their types
- another type of white blood cell
- has receptor proteins which bind to complementary antigen presented by phagocytes
- helper T-cells release signals that activate other phagocytes, and B-cells
- cytotoxic T-cells kill abnormal and foreign cells
What are B-cells
- a B-cell is another type of white blood cell
- covered with antibodies to create an antibody-antigen complex
- process is called clonal selection, different shaped antibodies bind to complementary antigens
- B-cells divide into plasma cells
What is antibody production
- plasma cells, which are identical to the B-cell, secrete thousands of antibodies specific to the foreign antigen, called monoclonal antibodies
- an antibody has two binding sites, binding multiple pathogens together, process called agglutination
- leads to the destruction of pathogens
Antigen notes
- part of an organism or substance that is recognised as self, or foreign, which will generate an immune response
- allow immune system to recognise bacteria, viruses, fungi
- cancerous or pathogen infected cells are called antigen-presenting cells
Defence mechanisms
Specific - cell mediated response (T-Cells) or humoral response (B-Cells)
Non specific - physical barriers (skin, etc) or phagocytosis
Primary response notes
- plasma cells secrete antibodies
- 200l antibodies a second
- responsible for immediate response
Secondary response notes
- memory cells circulate in blood
- remember antibodies to fight off pathogens next time
- secondary response is from memory cells
What is antigenic variability
- when a pathogen changes its surface antigens
HIV notes
- human immunodeficiency virus
- infects and kills helpers T-cells, which act as host cells
- immune system is unable to create an effective response
- replicates rapidly, person may experience severe flu-like symptoms
AIDS symptoms
- people are classified as having AIDS when the HIV has caused their immune system to fail, it is diagnosed through symptoms of this.
Viral replication steps
1) attachment - virus attaches to surface of host cell
2) entry - viral DNA/RNA enters host cell
3) replication - viral DNA/RNA replicates and new viral proteins are made, forming new capsids
4) assembly - new viral particles are assembled
5) release - host cell bursts (lyses) releasing newly made viruses
Entry of viruses into cell
1) direct penetration of naked virus, genome enters while capsid remains on surface
2) endocytosis
3) membrane fusion - capsid is removed once inside host cells
Exit of viruses from cell
Most commonly released through cell lysis
- enzyme called endolysin is coded for in viral nucleic acid
- endolysin attacks peptidoglycan in cell wall
- infected cell is destroyed
