Topic 3 Flashcards
What is a eukaryotic cell?
- A cell containing a nucleus and other membrane bound organelles
What is a prokaryotic cell?
- A cell with circular DNA and no membrane bound organelles
What is the structure and function of the nucleus?
- Structure: Double membrane perforated by pores. body in nucleus.
- Function: Control centre of cell which retains genetic info and makes proteins
What is the structure and function of the nucleolus?
- Structure: body in nucleus
- Function: makes rRNA and ribosomes
What is the structure and function of the ribosomes?
- Structure: made of RNA and proteins
- Function: site of protein synthesis and translates genetic material into proteins
What is the structure and function of the mitochondria?
- Structure: Double membrane with the inner one folded to form cristae.
- Function: site of aerobic respiration
What is the structure and function of the rough endoplasmic reticulum?
- Structure: system of interconnected flattened sacs with ribosomes attached to outer surface
- Function: Protein synthesis
What is the structure and function of the smooth endoplasmic reticulum?
- Structure: no ribosomes
- Function: makes lipids and carbs and transport when required
What is the structure and function of the cell surface membrane?
- Structure: Phospholipid bilayer containing proteins and other molecules
- Function: Controls movement as partially permeable membrane
What is the structure and function of centrioles?
- Structure: cylinders made of microtubules
- Function: Forms spindle during nuclear division
What is the structure and function of lysosomes?
- Structure: Spherical sacs of digestive enzymes formed by golgi
- Function: Involved in phagocytosis and autolysis.
What is the structure and function of the Golgi apparatus?
- Structure:
- Function: Modifies proteins and packages them into vesicles
What is the structure and function of the prokaryotic cell wall?
- Structure: Made of peptidoglycan
- Function: Cell support
What is the structure and function of the capsule?
- Structure: Sticky outer layer
- Function: Prokaryotes stick together and stop from being detected
What is the structure and function of the plasmids?
- Structure: Small loop of circular DNA
- Function: DNA separate from chromosomal DNA
What is the structure and function of the flagellum?
- Structure: tail-like structure
- Function: bacterial movement
What is the structure and function of the pili?
- Structure: Hair like structure on cell surface
- Function: adhere to surfaces
What is the structure and function of mesosomes?
- Structure: Infolding in plasma membrane
- Function: aerobic respiration and cell formation
How how proteins modified/trafficked?
- DNA to mRNA in transcription and mRNA leaves the nucleus to ribosome on rER.
- Proteins are made on the RER.
- Vesicles contain protein which is folded and processed at RER.
- Transported to Golgi apparatus where vesicles form and proteins are modified
- Vesicles pinched from Golgi apparatus and fuse with cell membrane releasing protein in exocytosis
What is the equation for magnification?
Magnification = image size/actual size
What is the difference between a light and electron microscope?
- Light: uses light to form image and has low resolution and low magnification
- Electron: uses electrons to form image and has much higher resolution and magnification
What is the difference between resolution and magnification?
- Resolution is the ability to distinguish between 2 points
- Magnification is how enlarged an image is compared to a specimen
What are tissues?
- Group of cells that work together to form the same function
What are organs?
- Group of tissues which work together to form the same function
What are organ systems?
- Organisation of organs which perform related functions
What are the 3 stages of Interphase?
- G1, cell grows
- S, synthesis of DNA + replication
- G2, proteins synthesised + reorganisation
What is mitosis?
- Two identical sister chromatids separate to produce genetically identical cells
What happens in Prophase?
- Nuclear envelope breaks down
- Chromosomes condense
- Centrioles form spindle fibres
What happens in Metaphase?
- Chromosomes align at cell equator
- Spindle fibres attach to chromosome centromeres
What happens in Anaphase?
- Spindle fibres split centromere
- One chromatid to each end
What happens in Telophase?
- Chromosomes de-condense and spindle fibres break
- Nuclear envelope reforms so two separate nuclei
What happens in cytokinesis?
- Whole cell divides
- Two identical diploid daughter cells
What is the importance of mitosis?
- Asexual reproduction
- Genetically identical
- Growth
- Repair
What happens in Meiosis I?
- Chromosomes are replicated in interphase.
- Homologous pairs of chromosomes are separated to produce 2 haploid nuclei.
What happens in meiosis II?
- Sister chromatids are separated
- 4 haploid nuclei produced
What is crossing over?
- Sections of DNA are exchanged between homologous chromosomes
- Same genes, different alleles
What is independent assortment?
- Chromosomes are randomly assorted when they line up on the cell equator.
How does meiosis produce genetic variation?
- Through non identical gametes
- Independent assortment of chromosomes
- Crossing over of alleles in chromatids
What do gamete cells fuse to form?
- One zygote
- Gametes have haploid cells and fuse to form diploid cells
What are homologous chromosomes?
- Chromosomes with same genes but different alleles
What are the adaptations of sperm cells?
- Acrosome, contains digestive enzymes to hydrolyse zona pellucida
- Flagellum, for motility towards egg
- Mitochondria, ATP for respiration and swimming
What are the adaptations of an egg cell?
- Zona pellucida hardens to prevent polyspermy
- Follicle cells provide protective coating
- Cytoplasm contains nutrients for the embryo
What happens in the acrosome reaction?
- Acrosome of sperm fuses with egg cell membrane and releases digestive enzymes
- Hydrolyses zona pellucida
- Release chromosomes
What is the locus of a gene?
- The position of a gene on a chromosome
What sex chromosomes do males have vs females?
- Males = XY
- Females = XX
When is an allele more likely to be expressed in the phenotypes of males?
- If there is a recessive allele present on the non-homologous portion of the X chromosome.
- Because they only have one X they show sex linked conditions.
What happens in the cortical reaction?
- Cortical granules are released from ovum via exocytosis
- Released into the zona pellucida which thickens and hardens
- Prevents polyspermy
What are stem cells?
- Unspecialised cells that are able to express all their genes.
- Become more specialised to their function.
What is cell differentiation?
- Where stem cells become more specialised into different cell types.
- Cells express fewer genes
How is gene expression controlled?
- By preventing DNA turning into protein
- Stopping transcription of mRNA
- Stopping translation of mRNA into protein.
What happens when a cell is totipotent?
- Cells have the ability to differentiate into any type of cell
- eg. embryonic stem cells
What happens when a cell is pluripotent?
- Cells can turn into most types of cells
- eg. blood cells
What happens when a cell us unipotent?
- Cells can only turn into one single cell
- eg. heart cell
What are epigenetic changes?
- When gene expression is regulated by chemical modification to chromosomes
What makes up the epigenome?
- All the chemical tags attached to the DNA and histones
How can chromatin be chemically modified to alter gene expression?
- Signals from the environment cause chemical tags to be added to the histones or DNA.
- Changes how tightly packed the chromatin is.
- Methylation of DNA or histone modification via acetylation
What happens if the chromatin is too tightly packed?
- RNA polymerase cannot bind to the DNA
- No transcription
- No gene expressed
What is DNA methylation?
- Methyl group is added to the DNA
- Transcription factors are unable to bind to DNA as chromatin is tightly packed
- Switches genes off
What is demethylation?
- Switches genes back on
- Methyl group is removed and transcription can happen as chromatin isn’t packed
What is histone acetylation?
- Addition of acetyl group to histone protein
- Chromatin less condensed so genes are able to be transcribed
- Switches genes on
What is deacetylation?
- Removal of histone proteins
- Chromatin is more compact so inhibits transcription
- Switches genes off
How do transcription factors (activators + repressors) control gene transcription?
- Activate the genes are called activators, they bind to the start of the gene and help RNA polymerase to bind and transcribe the gene.
- Deactivate the genes are called repressors, prevent RNA polymerase from binding.
What is an operon?
- It is a section of DNA that contains a cluster of genes which are controlled by a single promoter
What happens to Lac Operon when no lactose is present?
- Regulatory gene is transcribed and translated to produce repressor protein
- The protein binds to operator region
- RNA polymerase is unable to bind
- No lactase is produced
What happens to Lac Operon when lactose is present?
- Lactose is present to binds to repressor protein and distorts it
- Prevents it binding to operator region
- RNA polymerase is able to bind to promotor region
- Lactase is produced
What is cancer?
- The abnormal growth of mutant cells
- Derived from genes regulating cell division
- Either benign or malignant
What are proto-oncogenes?
- They code for many products including growth factors, receptor proteins and cell cycle
What happens if there is a mutation of proto-oncogenes?
- Form oncogenes which cause constant cell division
- Causes division and growth into a tumour
What are tumour suppressor genes?
- They inhibit cell growth
What happens if there is a mutation of tumour suppressor genes?
- Cells grow at an increased rate as it is not inhibited.
- Cells accumulate.
What are the genetic risks of cancer?
- Inherit mutations of oncogenes or tumour suppressor genes
What are the lifestyle risks of cancer?
- Age
- Genetics
- Smoking
- Diet
- Obesity
- Exercise levels
What is natural selection?
- Process of evolution in which the environment can apply a selective force on individuals within a population
What is the 6 steps of natural selection?
- Genetic mutations create multiple alleles of genes within a population
- Creates intraspecific competition
- Particular, advantageous alleles are able to face challenges
- These characteristics are able to survive
- Reproduce and pass on advantageous alleles
- Next generation has higher proportion of it.
