Module 2: Cells Flashcards
explain kingdoms
5 kingdoms
animal and plant are multicellular
bacteria, fungi and protoctista are microorganisms
all made from cells
properties of all cells
DNA, ribosomes, cytoplasm, cell membrane
what are the 5 kingdoms?
animal plant bacteria fungi protoctista
why are viruses not defined as living organisms?
don’t have standard cell components
can’t perform living processes without a host cell
eukaryotic cells
animal/plant cell that has a membrane bound nucleus and membrane bound organelles
examples of membrane bound organelles
nucleus endoplasmic reticulum golgi lysosome mitochondria
prokaryotic cells
bacteria, has no membrane bound nucleus or membrane bound organelles
2 forms of reproduction
sexual
asexual
sexual reproduction
animals and some plants
uses 2 parents
each parent provides a gamete which fuses to form a zygote, zygote develops into an organism
asexual reproduction
microorganisms and some plants
uses 1 parent
genetically identical offspring
how does a zygote develop into an organism
zygote is a stem cell
divides by mitosis to make several stem cells
all stem cells differentiates into specialised cells
specialised cell divides by mitosis
different tissues form organs
organs form organ systems
surrounded by the body
define a tissue
a group of specialised cells
define an organ
made of different tissues working together
define an organ system
different organs working together
Organelles in an animal cell
Nucleus Endoplasmic reticulum Golgi Lysosomes Mitochondria Ribosomes Cytoplasm Cell membrane
Cytoplasm
Site of chemical reactions
Cell membrane
Controls what enters/leaves the cell
Holds cell contents together
Cell signalling
Structure of nucleus
Contains DNA
DNA wrapped around histones to form Chromatin
Nucleus has double membrane called nuclear envelope which contains nuclear pores
Centre is nucleolus which produces mRNA
Nucleoplasm which contains DNA/chromatin
2 types of Endoplasmic reticulum
Rough
Smooth
Rough endoplasmic reticulum
Ribosomes on surface
Makes proteins
Smooth endoplasmic reticulum
No ribosomes
Makes lipids/ carbohydrates
Golgi
Modifies and packages proteins
Packages into vesicles for transport
Digestive enzymes placed into lysosomes (vesicles with membranes around them)
Mitochondria
Site of aerobic respiration Releases energy Produces ATP Double membrane: -inner membrane=cristae (increases SA for enzymes of respiration) -middle section is matrix
Ribosomes
Attacted to RER
Site of protein synthesis
70S- smaller, found in bacteria
80s- bigger, found in eukaryotes
What’s a plant cell made of
Nucleus Endoplasmic reticulum Golgi Lysosomes Mitochondria Chloroplast Vacuole Ribosomes Cytoplasm Cell membrane Cell wall
Cell wall
Made of cellulose
Prevents cell from bursting or shrinking
Structure of chloroplast
Organelle for photosynthesis Double membrane Discs called thylakoid Which contain chlorophyll Stacks of thylakoid called granum Fluid called stroma
Vacuole
Surrounded by tonoplast membrane
Contains cell sap
What is bacteria made of
No nucleus- loose DNA in form of single loop and plasmid
No membrane bound organelles- smaller ribosomes, mesosomes
Cytosol
Cell membrane/cell wall (made of glycoprotein murein)
Some have a capsule and flagella
Capsule
Protect
Water loss prevention
Flagella
Movement
What is a virus made up of?
DNA or RNA (if RNA then will have RNA transcriptase to convert)
Capsid (protein coat)
Attachment proteins
Viral enzymes
Attachment proteins
Infects host cells by attaching using attachment protein
Send in DNA which uses cell to make viruses components and uses the cell membrane to make viral lipid coat
Produces copies of the virus and destroys host cell
What is a chromosome
DNA in coiled form
Formed during interphase of cell division (mitosis/meiosis) in animals/plants
Made of 2 identical/sister chromatids joined by a centromere
Carries 2 copies of the same DNA molecule
Homologous pair of chromosomes
A pair of chromosomes
1 maternal
1 paternal
Same genes but different alleles
Cell division
Formation of new cells in multicellular organisms
Mitosis and meiosis
Mitosis
Produces genetically identical cells for growth and repair of tissues
Meiosis
Produces genetically different haploid cells as gametes for sexual reproduction
What does mitosis produce
2 genetically identical cells
Diploid
Full set of chromosomes/DNA
Benefits of mitosis
Growth and repair of tissues
Stages of mitosis
Interphase
Mitosis
Cytokinesis
Three phases of interphase
G1: protein synthesis
S: DNA replication
G2: organelle synthesis
Mitosis process
Prophase: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
Metaphase: chromosomes line up in the middle of the cell, attach to spindle fibre via centromere
Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
Telophase: chromatids uncoil, nucleus reforms, leaves 2 genetically identical nuclei
Cytokinesis
Separates cell into 2
Each receives a nucleus and organelles/cytoplasm
What happens to DNA mass in mitosis
Halves
What happens to number of chromosomes in mitosis
Stays same
What is cancer
Formation of tumour due to uncontrolled cell division
How does uncontrolled cell division occur
Mutation of DNA/cells forming cancer cells
Mutation can occur randomly or due to mutagens
Cancer cells are rapidly dividing cells that spend less time in interphase and more time in other stages (mitosis)
Treatments for cancer
Surgery
Chemotherapy
Radiotherapy
Surgery
Aim is to remove tumour
Chemotherapy
Uses drugs that inhibit mitosis
But can also affect normal healthy cells causing side effects
Treatment given as regular doses to allow time for normal healthy cells to recover in number
Radiotherapy
Radiation used to destroy cancer cells
What does meiosis produce
4 genetically different cells
Haploid
Half amount of chromosome DNA
Benefits of meiosis
Produces gametes which will be used in sexual reproduction in animals and plants
2 gametes fuse to form a zygote, zygote develops into organisms
Stages of meiosis
Interphase
Meiosis 1
Meiosis 2
Cytokinesis
Meiosis 1
Prophase 1: DNA coils forming chromosomes, nucleus breaks down, spindle fibres form, crossing over occurs
Metaphase 1: homologous pairs of chromosomes line up at equator and attach to spindle fibre via centromere by random assortment
Anaphase 1: spindle fibres pull, homolgous pairs of chromosomes separate to opposite sides by independent segregation
Telophase 1: chromosomes uncoil, nucleus reforms (2 nuclei)
Meiosis 2
Prophase 2: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
Metaphase 2: chromosomes line up at equator, attach to spindle fibres via centromere randomly
Anaphase 2: spindle fibres pull, centromere splits, sister chromatids move to opposite ends by independent segregation
Telophase 2: chromatids uncoil, nucleus reforms (4 genetically different nuclei)
Cytokinesis in meiosis
Each cell into 4
How does meiosis produce variation
Crossing over
Independent segregation
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 combination of alleles
Independent segregation
Anaphase 1 of meiosis 1- homologous pairs of chromosomes separate
Anaphase 2 of meiosis 2- chromatids separate
Independent segregation produces a mix of alleles from paternal and maternal chromosomes in gamete
What happens to DNA mass in meiosis
Quarters
What happens to chromosome number in meiosis
Halves
Haploid
Bacteria cell division
Binary fission Copy DNA (single loop and plasmid) and separate into 2 new genetically identical bacteria (asexual reproduction)
3 types of microscopes
Light
Transmission electron
Scanning electron
Magnification
Englarging the physical appearance of an object
Highest magnification microscopes
TEM
SEM
LM
How to calculate magnification
Image= actual x magnification
1mm to micrometer
1000
1mm to nanometre
1,000,000
Why can organelles appear different in images
Viewed from different angles and different depths
Definition of resolution
Minimum distance apart two objects can be so they are still distinguished separately
Which microscope has highest resolution
TEM
SEM
LM
Why do electron microscopes have a higher resolution
Electrons have a shorter wavelength than light
Difference between TEM and SEM
TEM the electrons pass through the specimen
SEM the electrons bounce off the surface of the specimen
Advantage and disadvantage of TEM
+highest magnification and resolution
- works in a vacuum so can only observe dead specimen, specimen must be thin, 2d black and white image is produced
Advantage and disadvantage of SEM
+produces 3D image
- works in a vacuum so can only observe dead specimen, black and white image
Process of cell fractionation
breakdown tissues into cells using pestle and mortar
Add cold isotonic buffer solution
Homogenize using a blender to release organelles
Centrifuges and increasing speeds, intensities and time
Supernatant respan
Pellets are formed (nucleus, chloroplast,mitochondria, endoplasmic reticulum golgi and lysosomes, ribosomes
Reason for conditions of buffer solution
Cold- reduce enzyme activity
Isotonic-sane water potential so organelle doesn’t shrink or burst
Buffer- maintains constant ph Incase lysosomes burst and release enzymes
Order of pellet formation in cell fractionation
Nucleus Chloroplasts Mitochondria Endoplasmic reticulum, golgi, lysosomes Ribosomes
Simple vs facilitated diffusion
Simple- molecules move directly through the phospholipid bilayer
Facilitated-molecules pass through transport proteins (large use carrier and charged use channel)
Factors affecting the rate of diffusion
Surface area (increase=increase the rat3 o& diffusion) Concentration gradient (increase= increase rate) Thickness( decrease=decrease diffusion distance=increased rate of diffusion) Temperature(increase=increase kinetic energy= molecules move faster= increased rate of diffusion) Size of molecules (smaller molecules=increased rate of diffusion)
Ficks law
Rate of diffusion is proportional to (surface area x concentration gradient)/ thickness
Osmosis definition
Movement of water molecules from an area of high water potential to an area of lower water potential across a partially permeable membrane
Which liquid has the highest water potential
Distilled/pure water
Value of 0kPa
Lower water potential by adding solutes
Water moves from less negative water potential to more negative water potential
Surround animal cell with pure water?
Swells and bursts
Osmotic lysis
Surround plant cell with pure water?
Swells but doesn’t burst
Cell wall prevents it from bursting
Made of cellulose
Cell is turgid
Surround animal cell with conc sugar/salt solution
Shrinks
Water leaves by osmosis
Surround plant cell with conc salt/sugar solution
Water leaves by osmosis
Cell wall prevents shrinkage so cell stays rigid
Protoplast shrinks
Cell is plasmolysed
Active transport definition
Movement of molecules from an area of low concentration to an area of high concentration against the concentration gradient using ATP and carrier proteins
Process of active transport
Molecules in an area of low concentration bind to carrier protein
ATP breaks down to ADP and Pi and energy
Pi and energy cause the carrier protein to change shape when Pi binds to it
Carrier protein releases molecules on opposite side in the area of high concentration
Carrier proteins releases attached Pi to return to its original shape
Enzymes of carbohydrate digestion and their products
Starch glycogen (salivary amylase in mouth,pancreatic amylase in small intestine) into maltose Maltose (maltase on lining of small intestine)into glucose Lactose(lactase on lining of small intestine) into glucose and galactose Sucrose (sucrose on lining of small intestine) into glucose and fructose
Enzymes of protein digestion
Endopeptidase (in stomach) hydrolysis peptide bonds in the middle of the polypeptide chain into many smaller chains
Exopeptidase (in small intestine) hydrolysis peptide bonds at the end of the chain into dipeptides
Dipeptidase (lining of the small intestine) hydrolyses dipeptides into amino acids
Enzymes of lipid digestion
Lipase in small intestine leaves monoglyceride and two fatty acids
Adaptations of the small intestine for absorption
Folded to form villus for increased surface area
Cells lining the small intestine have microvilli to increase surface area
Walls of small intestine is thin for short diffusion distance
Rich blood supply to maintain the concentration gradient
Cells lining the small intestine have transport proteins, enzymes (Maltase,lactase,sucrase,dipeptidase) and many mitochondria
Absorption of glucose and amino acids in small intestine
Sodium ions are actively transported from the cells lining the small intestine into the blood
Lowers the sodium ion concentration in the cell
Sodium ions move from lumen of small intestine into the cell
Pulls in glucose and amino acids via a co transport protein
Glucose and Amino acids build up in the cell and move into the blood via diffusion
Absorption of monglycerides and fatty acids
Lipids initially emulsified by bile into micelles
Micelles digested by lipase into monglycerides and two fatty acids
Monoglycerides and fatty acids absorbed by cells lining small intestine by simple diffusion
Form a chylomicron (lipid+cholesterol+lipoprotein)
Enters lymph as lacteal then enters blood
What is lactose intolerance
Person doesn’t make lactase
Lactose remains undigested
Undigested lactose in lumen of intestine lowers its water potential so water enters the lumen by osmosis leading to water faeces
Undigested lactose breakdown by microorganisms in large intestine giving off gas
Pathogen definition
Microorganism that causes disease
Body’s three defenses against pathogens
Barriers (prevent pathogens entering the body)
Phagocytes (phagocytosis and stimulate specific response)
Specific response (uses lymphocytes to produce memory cells and antibodies)
What are the barriers in pathogen defense
Skin-impermeable barrier of keratin
Cilia and mucus in the lungs
Stomach acid-denatures and breaks down pathogens
Process of phagocytosis
Pathogen releases chemoattractants
Attracts the phagocyte
Phagocyte binds to the pathogens cell surface proteins non specifically
Phagocyte engulfs the pathogen
Forms a phagosome around the pathogen
Lysosomes inside the phagocyte release lysozymes into the phagosome
Breaks down the pathogen by hydrolysis
Phagocyte presents antigens on its own cell surface membrane
Process of the specific immune response
Phagocytes perform phagocytosis and present antigens on their own cell surface membrane
T cells bind to the antigens and become stimulated
They divide by mitosis to form: t helper cells, cytotoxic T cells and memory T cells
T helper cells stimulate B cells
Cytotoxic T cells destroy cells infected by virus as they release performing to make holes in the membrane
T memory cells provide long term immunity
B cells engulf and present antigens on their surface and the t helper cells bind to this
Stimulates B cells to divide by mitosis to form plasma cells and memory cells
Plasma cells make antibodies and memory cells provide long term immunity
Antigen definition
Protein on the surface of a pathogen that stimulates an immune response
How does the immune response lead to production of antibodies
Phagocytes stimulate T cells T cell form t helper cells T helper cells stimulate B cells B cells form plasma cells Plasma cells make antibodies
What is an antibody
Globular protein
Made by plasma cells
Has 3 regions: variable region, hinge region, constant region
What are the three regions of an antibody
Variable
Hinge
Constant
What do the three regions of an antibody do?
Variable- different shape in each antibody, contains antigen binding sites, Bind to complementary antigens on a pathogen to form an antigen antibody complex to destroy the pathogen
Hinge-give antibody flexibility
Constant- same shape in all antibodies, binds to phagocytes to help with phagocytosis
How do memory cells work
Made during the specific immune response after a new infection by a pathogen (primary infection)
B and T cells remain in the blood
Upon secondary infection the memory cells will recognize the pathogen and produce antibodies rapidly to a large amount
Pathogen is killed before it can harm
Immunity
How does a vaccine programmer produce immunity
Involves giving an injection that contains dead/weakened form of a pathogen that carry antigens which stimulates the immune response leading to the production of antibodies and memory cells
Active immunity
Individual has memory cells
Make their own antibodies
Provides long term immunity
Passive immunity
Person given antibodies
These work then die
No long term immunity
No memory cells
How does active immunity occur
Naturally-primary infection
Artificially-vaccination
How does passive immunity occur
Naturally-mother to baby via placenta or breast milk
Artificially- by injection
Successful vaccination programme
Produce suitable vaccine (effective by making memory cells, doesn’t cause disease, no major side effects, low cost, easy administration)
Herd immunity
What is herd immunity
When a large population of the population is vaccinated therefore most people will be immune, increases chances of a non-immune person coming into contact with immune person so the pathogen has no where to go and will die out
Problems with vaccination programmes
Vaccine doesn’t work Vaccine isn’t safe Many strains of a pathogen Can’t achieve herd immunity Antigenic variability
Antigenic variability
The pathogen mutates Antigen changes shape Memory cells no longer complementary Doesn’t recognize the pathogen Therefore the pathogen can re harm
What is HIV/AIDS
HIV is pathogen
AIDS is infectious disease
HIV spreads by fluid
Damages t helper cells so person has no defense against pathogens leading to aids
