semester 1: biology exam revision

prokaryotes

• lack membrane bound organelles: ribosomes

• only membrane is plasma membrane

• uni cellular

• bacteria and archeans

villi

• villi found in the small intestine has a large SA:V to maximise absorption of nutrients

• damaged villi = malnutrition

eukaryotes

• membrane bound organelle

• nucleus

• mini compartments

• animals, plants, fungi

• plasma membrane: controls what enters and exits (DNA, ribosomes)

label digestive system

similarities + differences in eukaryotes and prokaryotes

SA:V ratio

• big = decrease SA:V - slower rate of exchange for nutrients and waste

• small = increase SA:V - faster rate of nutrients and waste

golgi complex + process

• membranes sacs that package proteins out of the cells via vesicles - has a high SA: V for faster exchange

  1. proteins are made at the rough ER (pepsin) that moves to the goldi complex where proteins are modified and packaged for secretory

  2. secretory vesicle moves to the membrane, binds and is released via exocytosis

  3. exports substances out of the cell - no Golgi = no modification of packaging for removal

chloroplasts

only found in plants

• photosynthesis is the conversion of sunlight energy to chemical energy

• has 2 jobs: catch the sunlight, green colouration

• has more than 1 membrane: each membrane has an outer membrane, inner membrane stacks called grana with large SA: V —> more sunlight absorbed —> more glucose stacks = more photosynthesis

plasma membrane

entry and exit of dissolved substances in and out of the cell

• partially permeable = only allows certain dissolved materials to pass through

phospholipid

• hydrophobic = scared of water (fats, lipids and steroids) and goes straight through the membrane

• hydrophilic = likes water (glucose and amino acids) and uses a protein channel to repel them

draw a phospholipid

simple diffusion

net movement of particles from a high solute concentration to a low solute concentration

• does not require energy

facilitated diffusion

movement of some substances aided by a carrier protein

• no energy required

• low solute concentration —> high solute concentration with assisted protein channel

carrier proteins

open on only one side

protein channels

open to both sides

osmosis

movement of water across a partially permeable membrane without an input of energy

• low solute concentration —> high solute concentration

osmosis in plant cells

1. hypertonic solution: water leaves —> high solute outside —> cell decreases in size (plasmolyzed)

2. isotonic solution: balance

3. hypotonic: water enters —> high solute inside —> turgid and chonk

active transport

net movement of substances in/out of cell against concentration gradient

• needs energy (ATP)

• draw diagram

binary fission

sexual reproduction where one parent organism produces offspring genetically identical to it

• daughter cell = identical

• no gametes (sex cells) involved

• in prokaryotes and protists meaning no mitosis = no stages

• faster than eukaryote process as simpler

mitosis

the longest process where the division of a cell produces 2 daughter cells that are identical to the parent cell

• in eukaryotes

• chromosomes are single-stranded but when mitosis occurs it becomes double-stranded

• centromere - spindle fibres attach and split chromosomes

interphase

chromosomes are not visible but are duplicated

prophase

nuclear disappears, chromosomes become visible and thicken + double-stranded and centrosome visible

metaphase

chromosomes line up in the middle of the cell with spindle fibres attached to either side of the cell

anaphase

spindle fibres contract and pull chromosomes to either side to divide and separate with duplicated chromosomes on each side

telophase

spindle fibres disappear and chromosomes are less visible + new nuclear membranes form around each group of membranes

• cell plate and firm cell wall in plant cell, cleavage furrow in animal cell

cytokinesis (not included)

cytoplasm divides and new membrane forms, enclosing and forming 2 separate cells

mitosis - cell cycle

time taken for a new cell to mature and give rise to 2 new cells

• ensured DNA is passed from parent to daughter cells with no errors

• 2 checkpoints:

1. G2: check to see if there is an error in DNA or damage

2. metaphase (checkpoint 2 before chromosomes splt): where chromosomes line up and attached to spindles to make sure it can split evenly

• if anything goes wrong, apoptosis occurs

G1 phase

where cell contents duplicate

S phase

46 chromosomes in the cell are duplicated by replication

G2 phase

checks to see if there are any mistakes and corrects any damages or repairs

label cell cycle

apoptosis

natural programmed death

• remove damage or non-functioning cells

• more cells than needed: energy wasted to maintain

• necrosis: unplanned cell death

apoptosis stages

cell responds to death signal and internal contents start to be digested

1. cell shrinks as cell volume decreases

2. plasma membrane starts to bleb due to plasma membrane detaching from cytoskeleton because of enzymes

3. nucleus and cell contents condense, fragments and cell brakes to form apoptotic bodies

4. apoptotic cells are engulfed by phagocytes via phagocytosis (draw)

stem cells

undifferentiated cells that have the ability to differentiate into organ or tissue specific cells with specialised functions

1. totipotent: any cell type e.g. zygotes

2. pluripotent: many cell types and form inner layer of blastocyst e.g. embryonic stem cells

3. multipotent: any family related group of cells

• multipotent blood marrow stem cells can develop into a rbs, wbc or platelet

mechanical digestion

large pieces broken down into smaller pieces through chewing via teeth and muscular movements: mouth and stomach

• if stomach is cut in half there is less room meaning less food can be eaten

chemical digestion

digestive enzymes speeding up breaking complex polymers (big) into simple monomers (small)

enzymes are involved to speed up the rate of reaction

intestines

small intestine is where most digestive enzymes and absorption of nutrients from food takes place: villi involved in only absorption

• liver is involved to make bile that breaks down fat = bile is stored in gallbladder

• no gall bladder = recommended less fatty foods as it cannot be broken down

osmoregulation

process of controlling water and solute (urea) concentration in the body

• if dehydrated:

  • osmoreceptors in hypothalamus detect and ADH is released which increases permeability of tubule to absorb more water

  • produces a small volume of dark yellow (high conc. urea) urine

  • osmotic pressure falls

hypotonic

a solution with a higher solute concentration inside the cell than the outside of the cell. therefore water moves in (lysed ot turgid)

hypertonic

a solution with a lower solute concentration inside the cell than the outside of the cell so water moves out (shrivelled in animal, plasmolyzed in plant)

isotonic

where there is no gain/loss by the cell as there is the same concentration

negative feedback

reverses a stimuli —> back to normal

positive feedback

enhances stimuli —> keeps ongoing

glucose

source of energy in organisms

insulin

controls the uptake by cells of glucose from blood

• decrease BGL via beta cells

glucagon

acts on the liver to release more glucose into the blood

• increases BGL via alpha cells

thyroid hormone

released from the thyroid and affect cellular differentiation growth and metabolism

• if thyroid is damaged or removed =reduction in thyroxine

• hypothyroidism (underactive) = hormone replacement tablets

• hyperthyroidism (overactive) = anti-thyroid drug, surgery

exercise and heat loss

evaporation: conversion of liquid water to vapour using heat

• evaporation of water via sweat from moist skin cools the flow near the surface

• reduce metabolic rate = reduce heat production (digestion)

vascular plants

xylem:

• transports water and dissolved minerals/ions upwards

phloem:

• transports sucrose are thin walled living cells

transpiration

transpiration is water loss from the stomata

• stops at night or when it is too hot because no light for stomata to open and to not lose water

• bad because it can lose too much water

• good because it causes h2o to evaporate which causes water to pull up (moves from root up)

• cohesion of water molecules allows movement up the xylem

valid

you get the results you’re supposed to get

precision

how close measurements of the same item are to each other

• repeat or average

non-maleficience

encourages people to minimise harm which needs to be considered if dealing with living org.

homeostasis

maintaining a relatively stable internal environment within narrow ranges despite changes in external environment

loop of henle

1. The ascending limb secretes ions into the surrounding tissue to create a hypertonic environment

2. Water moves from the ascending limb into the tissue via osmosis

3. Less filtrate produced as more water is reabsorbed into tissue

how are thyroxine levels regulated by negative feedback when too high and too low

• the anterior pituitary will not produce TSH which will stop the production of thyroxine and decrease levels

• The hypothalamus will not release TRH to stimulate the anterior pituitary, resulting in no further TSH to stimulate the thyroid gland, stopping the production of thyroxine.

why there is a constant production in thyroxine even when the production of TRH and TSH is regulated

• The thyroid gland does not need TSH to produce thyroxine

• Even when TSH reduces because of an increase of thyroxine, the thyroid gland will still be stimulated

advantage of eukaryotes

• can specialise in its own conditions

• carry out complex tasks

advantage of small prokaryote

• increase in SA: V for faster transport