Biology HSC exam Flashcards
Transcription
The process of turning genetic information stored in the DNA into an intermediary molecule mRNA.
- RNA polymerase binds to a ‘promoter’, which signals the DNA to unwind, and allows the enzyme to read the bases.
- Thew mRNA molecule is built, using complementary bases.
- mRNA detaches from the DNA strand.
Translation
The process of turning information encoded as mRNA into a polypeptide chain.
- mRNA attaches to a ribosome.
- The ribosome matches the codon and anticodons together.
- A polypeptide bond is formed, and continues to grow as amino acids are added
- Once a stop sequence is reached, the chain detaches and then folds.
DNA replication
DNA replication is the process by which an existing DNA molecule is copied to produce 2 identical DNA molecules.
· The enzyme topoisomerase relaxes the DNA from its coiled structure.
· The enzyme helicase unwinds & unzips the DNA molecule at a particular point (an origin of replication) making two template strands of DNA available.
· The hydrogen bonds between the nitrogenous base’s breaks.
· The enzyme primase synthesizes short RNA primers to start each new DNA strand or fragment. One of the strands is in the 3’ to 5’ direction, which is called the leading strand; the other is in the 5’ to 3’ direction and is called the lagging strand.
· The enzyme DNA polymerase catalyses the synthesis of the new DNA strands.
· DNA Polymerase helps the DNA nucleotides (which are readily available in the cell) match up with their complementary base on the template DNA (A&T, C&G). DNA polymerase continues to bond free nucleotides to the exposed bases according to the complementary base pairing rule until there are no more exposed bases.
· DNA ligase (enzyme) seals the two strands of DNA into double strands.
The result of DNA replication is two identical DNA molecules, made up of one old and one new strand which automatically coil back into a double helix.
Internal vs external fertilisation
Internal fertilisation involves the fusion of male and female gametes within a parent’s body. Internal fertilisation tends to occur between terrestrial animals.
External fertilisation involves the fusion of male and female gametes outside a parent’s body. External fertilisation tends to occur between aquatic animals.
Sexual vs asexual reproduction
Sexual reproduction, such as meiosis, is the process of forming a new organism from the fusion of the offspring’s parents’ gametes. Comparatively, asexual reproduction, such as mitosis, is the process of producing offspring from just one parent through cell division or mitosis.
The offspring as a result of sexual reproduction does not have genetic material that is identical to its parents. The offspring from asexual reproduction is a clone of its parent, meaning it has the same allele combinations as its parent.
components of the first line of defence
Skin: Tightly pack cells that form a protective layer.
Mucous membrane: Cells lining the opening of the body (respiratory tract, urinary and reproductive system) secrete a protective layer of mucous. It traps pathogens and foreign particles
Cilia: Hair-like projections which line the air-passages (nose and throat). Movement of the structures pushes pathogens away.
Chemical barriers: Substances such as stomach acid, the conditions in the small intestine and enzymes in the mouth all act to destroy pathogens.
Secretions: Fluids are routinely secreted from sweat glands, hair follicles and open passages in the body.
Phagocytes
These are leukocytes that engulf and break down pathogens in a process known as phagocytosis. Phagocytes include: • Neutrophils • Macrophages • Monocytes • Dendritic cells
phagocytosis
In phagocytosis, the phagocyte engulfs the foreign material, forming a phagosome. A lysosome fuses with the phagosome forming a phagolysosome. Within the phagolysosome the enzyme breaks down the foreign material into smaller pieces. The enzyme fragments are expelled from the phagocyte by exocytosis.
Natural Killer Cells
Natural Killer Cells are cells that attack viral-infected body cells. They are able to recognize cell surface markers (antigens) on body cells and destroy them by producing chemicals called perfins which are able to bind with foreign cell antigens on the surface and form pores (holes) that cause the cell to lyse (release cell contents). After the NK cell detects an infected or tumour cell, it induces programmed cell death, or apoptosis. Phagocytic cells then come along and digest the cell debris left behind.
The complement system
The complement system is a set of more than 30 different proteins which float around in the blood that assist other defence molecules in destroying pathogens. The complement proteins can stimulate phagocytes to become more active, attract phagocytes to the site of infection or destroy the membranes of invading pathogens.
inflammatory response
The inflammatory response is responsible for releasing several types of chemicals that enable the activation of phagocytes and other white blood cells to fight foreign substances. The body sends blood and fluid to the site of injury or infection, making it red, hot and swollen., allowing more blood flow to the site of infection and increasing access for phagocytes to enter.
naive B cells
After formation and maturing in the bone marrow, naive B cells move into the lymphatic system to circulate throughout the body. When a naive B cell encounters an antigen that fits its membrane-bound antibody, it quickly divides in order to become either a plasma B cell or a memory B cell.
naive T cells
Once formed in the bone marrow, naïve T cells migrate to the thymus (hence the name “T cell”) to mature. Each T-cell has a unique receptor that can fit with only one kind of antigen like a lock that can fit with only one shape of key. The antigens are bound to certain receptor molecules, called Major Histocompatibility Complex class 1 (MHCI) “SELF” and class 2 (MHCII) “NON-SELF”.
Cytotoxic T
Destroy cells that are recognised as foreign
Attach to a cell surface and release chemicals
Helper T
Stimulate the production of plasma cells by activating B lymphocytes and T cells to divide
Suppressor T
Turn off the immune response and suppress the production of antibodies
Memory T
Responsible for the secondary response
Clone when activated by an antigen after re-exposure
Plasma B
Presence of antigen stimulates cells to differentiate into plasma cells
Plasma cells produce immunoglobulins called antibodies that bind with a specific antigen
Memory B
Remain in the body after infection to recognise later infection
Produce secondary response that is faster
Pathogen
- When a pathogen enters the body, it is detected as foreign due to the presence of non-self-antigens on its surface
- Inflammation allows increased blood flow to the site. Increased permeability of blood vessels allow WBCs to migrate from the blood to infected tissue
- Non-specific responses, including phagocytosis, occur. Macrophages engulf pathogens and release cytokines to call other immune cells to infection.
- The macrophages present foreign antigens on their surface for recognition by B cells and helper T cells which are recruited to the site by interleukins (type of cytokine)
- B and T cells specific to the pathogen are selected by the antigens (clonal selection)
- B cells differentiate into plasma cells and secrete pathogen-specific antibodies to immobilise the foreign cells.
- Cytotoxic killer T cells attack pathogenic cells by releasing cytotoxins
- Memory B and T cells are produced
- Pathogen is cleared from the site
- Suppressor T cells dampen response and suppress killer T cells once the infection has passed
- Memory B and T cells remain circulating in the blood to provide long term immunity
Pathogen
- When a pathogen enters the body, it is detected as foreign due to the presence of non-self-antigens on its surface
- Inflammation allows increased blood flow to the site. Increased permeability of blood vessels allow WBCs to migrate from the blood to infected tissue
- Non-specific responses, including phagocytosis, occur. Macrophages engulf pathogens and release cytokines to call other immune cells to infection.
- The macrophages present foreign antigens on their surface for recognition by B cells and helper T cells which are recruited to the site by interleukins (type of cytokine)
- B and T cells specific to the pathogen are selected by the antigens (clonal selection)
- B cells differentiate into plasma cells and secrete pathogen-specific antibodies to immobilise the foreign cells.
- Cytotoxic killer T cells attack pathogenic cells by releasing cytotoxins
- Memory B and T cells are produced
- Pathogen is cleared from the site
- Suppressor T cells dampen response and suppress killer T cells once the infection has passed
- Memory B and T cells remain circulating in the blood to provide long term immunity
Bacteria example
Bacteria – Vibrio cholerae
Disease: cholera (a diarrheal infection)
Symptoms: diarrhea, vomiting, leg cramps, dehydration
Treatment: Oral Rehydration Solution (ORS) mixture of salt and sugar with 1 litre of water and drunk in large amounts. Other treatments include intravenous fluid replacement and antibiotics.
Vaccine: Vaxchora
Prevention: drink and use safe water; wash hands often with safe water; cook food well, peel fruits and vegetables.
Fungi example
Bacteria name: dermatophytosis
Disease: Tinea
Symptoms: darkening of the skin, peeling, red rashes, or scaly patches, blisters, cracking of the skin
Treatment: The treatment for ringworm is an antifungal medication
Vaccine: Ringvac
Prevention: maintain hygiene, keep skin dry, avoid sharing towels, avoid public swimming pools
Mode of transmission = direct contact, skin to skin contact, surfaces e.g. shower floor
Examples of types of tinea include athlete’s foot, ringworm
Protozoa example
Protozoa – Plasmodium falciparum
Disease: Malaria (transmitted via Anopheles mosquito)
Symptoms: fever, headache, chills, sweating; gastrointestinal (diarrhea, vomiting, nausea); pain in abdomen and muscles.
Treatment: prescription drugs to kill the parasite; antimalarial drugs are currently being researched and developed.
Vaccine: Mosquirix vaccine (RTS,S)
Prevention: avoid mosquito bites by using insect repellant; use mosquito net.
Protozoa example
Protozoa – Plasmodium falciparum
Disease: Malaria (transmitted via Anopheles mosquito)
Symptoms: fever, headache, chills, sweating; gastrointestinal (diarrhea, vomiting, nausea); pain in abdomen and muscles.
Treatment: prescription drugs to kill the parasite; antimalarial drugs are currently being researched and developed.
Vaccine: Mosquirix vaccine (RTS,S)
Prevention: avoid mosquito bites by using insect repellant; use mosquito net.
parasite example
Bovicola ovis
Disease: sheep lice
Symptoms: excessive itching and unwarranted wool loss, damaged wool.
Treatment: shearing fleece to remove lice
Prevention: stock-proof fences to prevent sheep from straying and catching lice (known as biosecurity); isolating infected sheep; stock introduced in farm should be quarantined and inspected for lice.
virus example
Virus – Severe Acute Respiratory Syndrome Coronavirus 2
Disease: coronavirus disease (COVID-19)
Symptoms: fever, dry cough, tiredness, conjunctivitis, diarrhea, aches and pains, shortness of breath
Treatment: rest, drink lots of fluids, and eat nutritious foods; self-isolate and visit the doctor.
Prevention: wear mask, sanatise, cough into elbow, maintain safe distance, stay home if feeling unwell.
Vaccine: Moderna, Pfizer
Prevention: quarantine, PPE
prion example
Prions – Bovine spongiform encephalopathy (BSE)
Disease: Mad cow disease (also Variant Creutzfeldt-Jakob disease through contaminated food – zoonotic disease in humans)
Symptoms: dementia, problems with coordination, psychosis, unresponsiveness, weight loss and drop in milk (for cattle), behavioural changes, trembling.
Treatment: no cure; treatment focuses on keeping patients as comfortable as possible.
Prevention: avoid feeding cattle rendered material from slaughtered animals and to isolate and destroy all infected animals.
Virus structure
Virus is classified as a non-cellular pathogen as they have living and non-living features. They are not made up of cells but rather they have a protein coat containing genetic information in the form of DNA or RNA. This means that they are able to pass on their genetic information via DNA/RNA replication and produce more virus via protein synthesis.
bacteria structure
Bacteria are unicellular, microscopic organisms without membrane-bound organelles. This means that they are prokaryotes and do not have cell membrane. They undergo asexual reproduction via the binary fission process.
Protozoan structure
Protozoans are unicellular, eukaryotic organisms. They mean that they have cell membranes although they don’t have cell wall. Similar to bacteria, they asexually reproduce via binary fission and have DNA as their genetic material.
fungi structure
Although fungi can be unicellular (e.g. yeast) or multicellular (e.g. mushroom), they are all eukaryotes. This means that they have membrane-bound organelles. They also have a rigid cell wall made from chitin. Unlike bacteria and protozoan, they are not motile (non-mobile). They reproduce via spores and spores rely on wind for transportation which germinates upon landing on a surface in a favourable environment such as presence of moisture and preferably cool temperatures. Fungi can either be living on dead tissue (known as saprophyte) or be parasites (thrive on living tissue).
prion structure
Prions are classified as non-cellular pathogen as they do not contain any DNA or RNA
Design and conduct a practical investigation relating to the microbial testing of water OR food samples
Equipment:
• Food sample (e.g. bread, yogurt and cheese)
• 6x Agar plates
• 1x Incoulating loop
• 1x Bunsen Burner
• sanitiser
• 3x Test tubes
• Pen & Labels
• Sticky tape
Procedure:
Step 1: Sterilise table surfaces using sanitizer
Step 2: Sterilise your inoculating loop by heating it in the flame of bunsen burner. (making sure it turns orange)
Step 3: Transfer small quantities of three different food sample into three test tubes with 2mL of distilled water and gently mash up the food samples.
Step 4: Dip your sterilised inoculating loop into the food sample in one of your test tube and wipe the food gently on the surface of your agar.
Step 5: Put on the agar plate lid and seal the plate using the sticky tape then label the food type on the lid.
Step 6: Heat your inoculating loop again and repeat
Step 7: Leave sealed agar plates as your control.
Step 8: Observe the number of microbial colonies that are formed in each agar plate and record observations.
Safety:
• Wear gloves to avoid being infection by bacteria.
• When you have sealed the agar plate, do not open it again.
• Take care of using the bunsen burner and hot inoculating loop.
• Wash your hands thoroughly using water and hand-wash solution before leaving the laboratory.
How do ears work:
When sound waves in the ear canal reach the ear drum, it vibrates at the same frequency. It passes these vibrations on to the middle ear bones. The ossicles receive vibrations from the ear drum. They amplify these vibrations and pass them on to the fluid in the inner ear. The organ of Corti in the inner ear contains hair cells that can detect vibrations. The movement of the hair cells causes their cilia to vibrate. These vibrations are converted into electrical nerve impulses that can be sent along the cochlear nerve to the brain to be interpreted as sound.
Hair cells in the inner ear can be damaged by exposure to noise. The hair cells for higher pitches are the first to encounter sound waves, and so experience more stress over time from noise exposure. This causes them to degenerate earlier than hairs for lower pitches.
hearing aids
Hearing aids receive sound through a microphone, which then converts the sound energy to electrical energy. The amplifier increases the loudness of the signals and then converts the electrical energy back to sound. This sound leaves the hearing aid through a speaker which directs the sound down the auditory canal.
Cochlear implant
A cochlea implant is an electronic device used for conductive hearing loss. Sound is detected by a microphone and transferred to a speech processor which sends a digital signal to the implant via the transmitter. The implant transforms the signal into electrical impulses. Electrodes stimulate the nerves in the cochlea, by passing the damaged hair cells and messages are sent along the auditory nerve.
Bone conduction implants
A bone conduction system consists of a small titanium implant, abutment and sound processor. Sound is transmitted as vibrations from the sound processor to the implant, through the bone to the inner ear.
How do the eyes work
- Light enters eye and passes through thin conjunctiva.
- Light passes through cornea, which refracts (bends) the light
- Light passes through pupil
- Optic nerve carries electrical impulses from retina to brain
- Retina detects and converts light impulses into electrical stimuli
- Light passes through lens, which refracts (bends) light to focus it on the retina
- Brain interprets electrical impulses to create an image
Myopia vs Hyperopia
Myopia – the eyeball is too long, and the light focuses in front of the retina, causing the image seen to be blurred/ not sharp.
Hyperopia – either the eyeball is too short, or the lens is not able to retract light sufficiently and the focal point of light entering the eye is behind the retina, again causing the image seen to be blurred/ not sharp
glasses and contact lenses
glasses and contact lenses correct vision by changing the angle at which light hits the cornea which adjusts for misshapen corneas that cause the focal point to deviate from the norm.
