Biology Exam Questions Practice

function of CRISPR in Prokaryotes

•  immune defense to protect bacteria from reinfection from bacteriophage

• Spacer - created using viral genome & integrated into the CRISPRE genome

• Repeats - used to separate each viral genome (spacer)

• CRISPR: short repeated segments of DNA separated by spacer sequences within the bacterial genome. The spacer sequences are ‘copied’ from a viral invaders genome. Acts as a ‘memory’ of past infection.

types of bonds

Hydrogen bonds	b/w complementary nitrogenous base of 2 secondary structure (b/w amine & carboxyl group of diff AA) what primers in PCR anneal with between R groups for tertiary strcutre
Phosphodiester (covalent)	join nucleotides (sugar of one & phosphate group of another) = strong what endonuclease cuts & ligase restores
peptide	Primary structure (b/w amino acids) rna catalyzes the formation of peptide bonds between amino acids
Disulfide	between cysteine amino acids (tertiary strcutre)

radiocarbon dating

• known that Carbon 14 decays to form nitrogen 14 with a half-life of 5730 years.

• Radiocarbon dating is a technique in which scientists compare the proportion of parent (C14) to daughter (N14) isotopes to calculate how many half lives have passed

After death, the organism stops taking in C-14, which radioactively decays into nitrogen-14 at a known rate. Carbon dating determines the approximate age of remains by measuring the ratio of stable carbon-12 to carbon-14 remaining; and using its half-life of approximately 5730 years (number of half-lives that have passed) 

ETC steps

NADH and FADH2 move to the intermembrane space and unload their H+

H+ builds up - creating a concentration gradient

H+ travels through ATP synthase - causing it to spin,

The kinetic energy allows for ADP + Pi to become ATP

H+ are accepted, bond to oxygen (final electron acceptor) - forming water which maintains the concentration gradient

fossilisation

1. Rapid burial after death = organisms dies and is buried quickly (low oxygen and hidden from scavengers)

2. Undisturbed = so that remains are intact and not broken up

   1. From scavenging animals/weather

3. Decomposition prevented = conditions must be such that bacteria (and fungi) that normally decompose dead tissue cannot survive

   1. Include: constant cold temperatures, dehydration, high acidity, lack of oxygen, darkness

4. Downward pressure = from layers of sediments above

Plants physical defenses

• waxy cuticle forms a waterproof physical barrier over the leaf surface, preventing pathogens from entering the plant

• Thick bark is an external layer of dead cells preventing the entry of pathogens

• stomata may be closed to prevent pathogens entering; they may also be sunken and sit lower down

plants chemical defenses

• Defensins are antimicrobial proteins produced by plants that interfere with fungal cell membranes, inhibiting fungal growth

• Saponins are plant proteins that disrupt bacterial and fungal cell membranes, inhibiting their growth

symptoms of inflammation

redness - vasodilation of blood vessels, leading to red blood cells released into tissue

pain - swelling causes pressure on the surrounding tissue, which stimulates pain receptors and contributes to the pain

heat - increased blood flow

swelling - increased movement of fluid (blood & lymph) into tissues (due to increased capillary permeability) after vasodilation

allergic reaction steps

• Damaged or infected cells release cytokines to attract immune cells

• Mast cells bind to release histamine, this triggers:

  • Vasodilation = increased blood flow

    • Causing redness and heat

  • Increased permeability of capillary walls = migration of phagocytes to site of infection

    • Causing swelling and pain

• Return to pre-infection conditions

function of antibodies

Agglutionation: form antigen-antibody complexes, causing the antigens to clump together and make them more recognisable to phagocytes

Neutralization: prevent binding of pathogen to self-cells to neutralise harmful effects

Opsonisation: tag pathogens for destruction (by binding to surface antigens on pathogens to form antigen-antibody complexes), activating phagocytes and complement proteins - leading the destruction of the pathogen

Zoonotic disease

Infectious diseases that are transmitted from animals to humans

Epidemic

sudden increase in occurrence of a disease among a specific population in a given area at a particular time

Pandemic

an epidemic that has spread across multiple countries in different regions of the world

production of mAbs?

1. identify & isolate an antigen present on the target cell (e.g. cancer cell)

2. vaccinate an animal (mice) w/ isolated antigen, stimulating an immune response in the mouse; B cells induced to produce antibodies specific to the antigen & these are then extracted from the spleen of the animal

3. extracted B cells fused w/ rapidly-dividing cancerous human plasma cells (myeloma cells); results in hybridised cells (hybridomas)

• Usually, B cells cannot divide, but by fusing it w/ a tumor cells allows it to divide indefinitely

4. hybridomas screened so that only those producing the desired, relevant, specific antibody remain.

5. Grown in lab/cloned

• Spleen contains a mixture of B cells - only come for antibodies against antigen X --> get rid of other cells (

• The hybridomas that produce the specific antibody are cloned, which results in the mass production of these antibodies. 

6. The antibodies are then collected and purified before being administered to patients

• ensuring the monoclonal antibody preparation is pure and safe, particularly for immunocompromised patients.

relative dating

dates relative to the position of the fossil or relative to an index fossil of known age

Based on statigraphy; states that the oldest stratum is at the bottom and younger layers lie above can also be used.

Faunal selection = fossils contained in sedimentary rock strata succeed one another in a predictable order (with lower fossils being older than younger fossils), even when they are found in different places

• same sequence of fossils is found at another location, it is likely that the rock strata containing them are from the same geological time

1. fossils are arranged in the sedimentary rock in a vertical order

Limb Structure - bipedalism

• Bipedalism (selective advantage) = bipedal gait became more efficient when not climbing in trees

  • lengths of the legs become longer in comparison to their arms

    • better assists bipedal motion, preventing knuckle dragging

  • Pelvis shape becomes shorter & more bowl shaper

    • more support for the upper body whilst standing and walking upright

  • Leg attaches to the pelvis at an angle

    • walk upright more easily

    • Angle of the femur – knees angled inwards, placing feet under the body;

Consequences-based approach

central importance on the consideration of the consequences/effects of an action, aim to achieve maximization of positive outcomes/benefits and minimization of negative effects

• may allow an individual to break the rules to achieve the greatest good

duty/rule based approach

concerned with how people act; some actions are essentially good/bad, dependent on their nature and a clear set of rules

• humans have an obligation/duty to follow these ethical rules regardless of consequences that may be produced

virtue-based approach

reference to virtues (good, honest, caring)

- individual should be driven by their character, rather than by any fundamental rules or consequences; action can be justified simply for its virtues

- consideration is given to the virtue/moral character of the person carrying out the action, providing guidance about the characteristics and behaviors a good person would seek to achieve to then be able to act in the right way

- which action would a good person choose (is it of moral character to be…)

integrity

honest reporting of all sources of information and communication of results, whether favorable or unfavorable

Justice

ensure that there is fair consideration of competing claims, no unfair burden on a particular group from an action & fair distribution and access to the benefits of an action

Beneficence:

commitment to maximizing benefits and minimizing the risks/harms involved in taking a particular position or course of action.

Non-maleficence:

involves avoiding the causations of harm so that the harm resulting from any position or course of action should not be disproportionate to the benefits from any position or course of action

Respect

consideration of the extent to which living things have an (inherent/functional worth) intrinsic value and/or instrumental value;

• valuing the differences between people in terms of their beliefs, values and freedoms.

• consideration of the capacity of living things to make their own decisions; and when living things have diminished capacity to make their own decisions ensuring that they are empowered where possible and protected as necessary

CO2 affect on pH + alkaline enviorement?

lowers pH by increasing acidity

Alkaline environment = high pH (low acidity)

Cas9 vs restriction enzymes

Cas9 is guided by a gRNA (or sgRNA), which determines the target sequence, whereas a restriction endonuclease cuts at a specific, fixed DNA sequence known as a restriction site.

biochemical pathway:

a series of linked biochemical reactions where the product of one reaction is the reactant of the next

uses enzymes

allows for the efficeint & controlled production of complex molecules (ATP)

enzymes

biological catalyst, that lowers activation energy to increase the rate of reaction within living cells without being consumed in the process

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allotrostic site

a binding site (outside of the active site) on the enzyme where OTHER molecules that are not the substrate can bind

coenzyme & examples

non-protein molecules that contribute to the activity and stability of enzymes.

• Type of organic cofactor

• ATP - energy transfer (carries energy from one site to another)

  NADH/FADH2 - transfer of electrons and protons (carries energy from one site to another)

enzyme avalibility for PS/CR…how changed?

amount of enzyme can be raised or lowered through gene regulation

affect of inhibitors? on graph

LI stage of PS

1. CO2 is taken in (powered by ATP)

2. ATP breaks apart CO2 and NADPH unloads H+ ions

3. C’s, O’s, and H’s recombine into C6H12O6 (Glucose)

1. additional oxygen molecules from CO2 and hydrogen ions from NADPH bind together to create water

• Doesn’t require light, but requires light-dependent stage

case study

Investigating a real or hypothetical situation that reflects what would be expected to happen in a real-world scenario

classification and identification

Classification involves the arrangement of objects, events or phenomena into specific sets. Identification involves the exploring of objects, events or phenomena belonging to particular sets or a new set.

correlation study

Conducting investigations to understand the associations that exist between variables without manipulation by the investigator

fieldwork

Making observations external to a classroom environment through the use of sampling, observations and surveys

literature review

Exploration and analysis of secondary data that usually relate to the findings and viewpoints of others

modelling

Constructing a model (physical, conceptual or mathematical) to help represent a phenomena or idea

product/process/system development

Designing an object or system that has technological applications

simulation

Using a model to study a real or theoretical concept