Module 2 Flashcards
Eukaryotic cell
Animal/ plant cell has membrane bound organelles ( eg nucleus, rer, Golgi )
Prokaryotic cells
Bacteria, has no membrane bound organelles
Sexual reproduction
In animal and some plants. Uses 2 parents( each provides a gamete which fusses to form a zygote, zygote develops into organism
Asexual reproduction
In microorganisms and some plants. Uses 1 parent to produce genetically identical offspring
How does a zygote develop into an organism
Zygote is a stem cell
Zygote divides by mitosis to make many stem cells
Each stem cel differentiates into specialised cell
Each specialised cell divides by mitosis to make many copies and form a tissue.
Different tissues join to form an organ, different organs join to form an organ system. This is surrounded by the body
Stem cell
Undifferentiated/unspecialised cell, can form any type of cell
Tissue
A group of specialised cells
Organ
Made of different tissues
Organ system
Different organs working together
Do ribosomes have a membrane
No
Structure of nucleus
Contains dna ( made of genes, genes code for making proteins).
Dna wrapped around histones to form chromatin
Double membrane, called nuclear envelope, which contains pores
At centre there’s nucleolus- produces mRNA
Rest of nucleus made of nucleoplasm( contains the dna/chromatin
Structure of chloroplast
Organelle for photosynthesis, double membrane, discs called thylakoids, thylakoids contain chlorophyll, stack of thylakoids called granum, thylakoids surrounded by fluid called stroma
Vacuole
Surrounded by a membrane called a tonoplast, contains cell sap ( water,sugar,minerals)
What’s bacteria made of
No nucleus so loose dna in form of single loop plasmids.
No membrane bound organelles
Cytoplasm
Cell membrane and cell wall ( made of murein/ peptidoglycan)
Some have a capsule and flagella
What is a virus made of
DNA or rna( if rna, it contains reverse transcriptase to turn rna into dna )
Protein coat called capsid and lipid coat
Attachment proteins on outside
How do viruses infect host cells
Infect host cells by attaching using their attachment protein, send in their dna which uses the cell to make the viruses components and uses the cell membrane to make the viruses lipid coat, hence, producing copies of the virus and destroying the host cell
What is a chromosome
DNA coiled form
Formed during interphase of cell division( mitosis/meiosis)in animal/plants
Made of 2 identical/sister chromatids joined by a centromere
Carries 2 copies of the same dna molecule
What’s a homologous pair of chromosomes
A pair of chromosomes ( 1 from mother the other from father)
Carries same genes but different alleles - there are 23 pairs in humans
Mitosis definition
Produces genetically identical cells for growth and repair of tissues
Meiosis definition
Produces genetically different haploid cells as gametes for sexual reproduction
Prophase
DNA coils to form chromosomes, nucleus breakdown, spindle fibre’s form
Metaphase
Chromosomes line up in middles of cell and attach to spindle fibres via centromere
Anaphase
Spindle Fibres pull, centromere splits, sister chromatids move to opposite sides
Telophase
Chromatids uncoil, nucleus reforms ( left with 2 genetically identical nuclei )
Cytokinesis
Separating into 2 cells
What happens to mass in mitosis
Halves
What happens to chromosomes number in mitosis
Stays the same ( diploid )
What does meiosis produce
4 genetically different cells, haploid ( half the amount of chromosomes/dna)
Meiosis 1- prophase
DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
Crossing. Over occurs
Meiosis 1 - metaphase
Homologous pair of chromosomes line up in middle of cell and attach spindle fibres via centromere by random assortment
Meiosis 1 - anaphase
Spindle fibres pull, homologous pair of chromosomes separate to opposite sides by independent segregation
Meiosis 1 - telophase
Chromosomes uncoil, nucleus reforms ( left with 2 nuclei )
Meiosis 11- prophase
DNA coils to form chromosomes, nucleus breaks down , spindle fibres form
Meiosis 11- metaphase
Chromosomes line up in middle of cell and attach to spindle fibre via centromere by random assortment
Meiosis 11- anaphase
Spindle fibres pull, centromere splits , sister chromatids move to opposite sides by independent segregation
Meiosis 11- telophase
Chromatids uncoil, nucleus reforms ( left with 4 genetically different nuclei )
How does meiosis produce variation
Crossing over and independent segregation
What’s independent segregation
In anaphase 1 and meiosis 1 - the homologous pairs of chromosomes separate
In anaphase 11 and meiosis 11- the chromatids separate
Independent segregation produces a mis of alleles from paternal and maternal chromosomes in gametes
What’s crossing over
Occurs in prophase 1 of meiosis 1
Homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids- produces new combinations of alleles
How do bacteria do cell division
Binary fission
Copy their dna ( single loop and plasmids ) and then separte into 2 new genetically identical bacteria ( asexual reproductive)
2 types of microscopes
Light and electron( transmit ion and scanning )
Magnification
How much larger the image side is compared to the actual size
Magnification = image size /actual size
Which microscope has higher magnification
TEM > SEM > LM
Which microscope has higher resolution
TEM > SEM > LM
Advantages / disadvantage of SEM
produces 3D image
Only works in a vacuum so can only observe dead specimens, black and white image
, artefacts
Simple diffusion
Molecules move directly through the phospholipid bilayer
Facilitated diffusion
Molecules pass through transport proteins ( large use carrier, charged use channel)
Factors that affects rate of diffusion
Surface area ( increase = increase rate of diffusion ) Concentration gradient ( increase = increase diffusion ) Thickness ( decreases= decrease in diffusion distance = increase diffusion) Temperature ( increase = increase kinetic energy = molecules move faster = increase rate of diffusion) Size of molecule ( smaller molecules = increase rate of diffusion )
What’s ficks law
( Surface area x conc gradient) / Thickness
What happens if you surround animal cell with pure water
Swells and bursts ( water enter via osmos )
What happens when you surround plant cells with pure water
Swells but does not burst
Cell wall prevents it from bursting , made of cellulose - strong material
The cells is turgid
What happens when you surround animal cell with conc sugar/salt solution
Shrinks ( water leaves by osmosis )
What happens when you surround plant cell with conc sugar/salt solution
Water leaves via osmosis
Cell wall prevents cell from shrinking, keeps it rigid
The protoplast ( cell membrane plus contents ) shrink
The cell is plasmolysed
Describe process of active transport
Molecules ( in low conc) bind to carrrier protein
ATP breakdown down to adp, pi and energy ,
the pi and energy cause carrier protein to change shape
Carrier proteins release molecules on opposite side ( in area of high conc )
The carrier protein releases the attached pic to return to its original shape
Enzymes of protein digestion
Endopeptidase( in stomach ), hydrolyses peptide bonds in middle of polypeptide chain into many smaller chains
Exopeptidase( in small intestines ) hydrolyses peptide bonds at end of chains to leave dipeptides
Deipeptidase ( on lining of SI ) hydrolyse dipeptides into amino acids
Enzymes of lipid digestion
Lipase in small intestine leaves monoglycerides and 2 fatty acids
Adaptions of SI for absorption
Folded to form villus ( large SA)
cells lining SI have microvilli. ( large SA )
wall of SI is thin ( short diffusion pathway)
Rich blood supply ( maintains conc gradient )
What’s a pathogen
A disease causing micro-organism , eg bacteria, virus , fungi
Bacteria cause disease by producing toxins
Virus causes disease by producing toxins
Virus cause disease by dividing in cells causing them to burst
Body defences against pathogens
Barriers - prevents pathogens entering the body
Phagocytes - perform phagocytosis and stimulate specific response
Specific response - uses lymphocytes to produce memory cells and antibodies
What are the barriers against pathogens
Skin- an impermeable barrier made of keratin
Cilia and mucus in lungs
Stomach acid - denatures / breakdown pathogens
Describe the process of phagocytosis
Pathogen releases chemicals, this attracts the phagocyte, the phagocyte binds to the pathogen and engulfs it , forms a phagosome around pathogen , Lysosomes inside the phagocyte releases digestive enzymes into the phagosome , breaking down the pathogen by hydrolysis
Describe the specific response
Phagocytes perform phagocytosis without destroying the antigen, they place antigens on their surface, presenting the. T cells bind to the antigen and become stimulated , they divide by mitosis to form 3 types of cells ( t helper , t killer and t memory )
T helper stimulate B cells , t killer kill infected cells , t memory provide long term immunity
B cells
Engulf and present antigens on their surface, the t helper cells bind to this
The B cells become stimulated and divide by mitosis to make plasm cells and b memory cells.
Plasma cells make antibodies
B memory cells provide long term immunity
What is an antigen
A protein on the surface of a pathogen that stimulates an immune response
What is an antibody
A globular protein, made by plasma cells , has 3 regions
Variable region on an antibody
Has a different shape in each antibody, contains the antigen binding sites, these bind to complimentary antigens ( on a pathogen ) to form an antigen- antibody complex , destroying the pathogen
Hinge region on an antibody
Gives the antibody flexibility
Constant region on an antibody
The same shoe in all antibodies, binds to phagocytes to help with phagocytosis
Active immunity
Individual has memory cells - can make their own antibodies and provides long term immunity
Passive immunity
Person given antibodies, these work then die, no long term immunity, so no memory cells
How does active immunity occur
Naturally= by primary infection Artificially = by vaccination
How does passive immunity occur
Nationally = from mother to baby ( placenta or breast milk) Artificially = by injection
Successful vaccination programme
Produces suitable vaccine ( effective , doesn’t cause disease , no major side effects, low cost, easily produced/transported/stored/administered)
Herd immunity
What is herd immunity
When a large proportion of the population is vaccinated, therefore most people will be immune, only a few will not be immune, increases chance of non-immune person
Problems with vaccination programmes
Vaccine doesn’t work Vaccine not safe Many strains of pathogens Cannot achieve herd immunity Antigenic variability
What is antigenic variability
The pathogen mutates, the antigen changes shape, so the memory cells no longer complimentary- do no recognise the pathogen, therefore the pathogen can re harm
What is hiv/ aids
HIV = human immunodeficiency virus , AIDS = acquired immunodeficiency syndrome
HIV is the pathogen , AIDS is the infectious disease
HIV is spread by fluid to fluid contact ( unprotected sex, needle , mother to child)
What does HIV destroy
HIV damages and destroys T helper cells, therefore person no longer produces immune response and has no defence against pathogens/ infections ( AIDS )
Which AIDS individuals at risk from all sorts of pathogens/infections called opportunistic infections
