Biology SACE Stage 2 Topic 2 Revision Guide Flashcards

What are the three principles of Cell Theory?

• All living organisms are composed of one or more cells

• The cell is the basic structural and functional unit of life

• All cells arise from pre-existing cells

What are the principles of MODERN Cell Theory?

• Energy flow occurs within cells.

• DNA is passed from cell to cell.

• Cells share a similar chemical composition

Why is Cell Theory considered a unifying concept in biology?

All living organisms are linked because they all:

• are made up of cells

• use cells to perform life processes

• inherit DNA through cell division

• Share common cellular structures, suggesting a common evolutionary origin

What are the functions of the cell membrane?

• separates the cell from its environment

• controls the movement of substances in and out

• maintains homeostasis

• enables cell communication

• provides protection and structural support

Describe the fluidity of the Fluid Mosaic Model.

• phospholipids move laterally

• membrane is flexible and dynamic

Describe the mosaic of the Fluid Mosaic Model.

• proteins embedded throughout membrane

• cholesterol molecules regulate fluidity

• glycoproteins and glycolipids enable cell recognition, signalling, and adhesion

Describe the hydrophobic structure of a phospholipid.

• two non-polar tails

• water-repelling fatty acids

• binded by carbon-hydrogen chains

Describe the hydrophilic structure of a phospholipid.

• a polar head

• water-attracting region

• minded by hydrogen bonding

Why does the phospholipid bilayer form?

• it is the most thermodynamically stable arrangement for phospholipids

• phospholipids arrange themselves into a bilayer so that hydrophobic tails face inwards and hydrophilic heads face outwards

• this enables the heads to form hydrogen bonds with water

Where are chromosomes found in prokaryotes?

circular chromosome located in the nucleoid region

Where are chromosomes found in eukaryotes?

linear chromosome located inside the nucleus

Why do prokaryotic and eukaryotic cells support common ancestry?

both contain:

• DNA

• cytoplasm

• ribosomes

• plasma membrane

these similarities suggest they evolved from a common ancestor

Structure of nucleus

• double membrane nuclear envelope

• nuclear pores

• contains chromatin

Function of nucleus

• stores DNA

• controls cellular activity

• site of transcription

Structure of nucleolus

• dense region inside of nucleus

Function of nucleolus

• site of rRNA synthesis

• assembles ribosomal subunits

Structure of mitochondria

• double membrane

• inner membrane filed into cristae to maximise SA:V for ATP synthesis

• matrix gel contains enzymes and DNA

Function of mitochondria

• aerobic respiration

• ATP production

Aerobic respiration

• cellular process of breaking down glucose

• occurs in the presence of oxygen

• produces ATP energy

Aerobic respiration

C₆H₁₂O₆ + 6O₂ —> 6CO₂ + 6H₂O

1st Stage of Aerobic Respiration

glycolysis

Describe Glycolysis

• glucose molecule is split into two pyruvate molecules

• does not require oxygen

• occurs in cytoplasm

2nd stage of Aerobic Respiration

The Link Reaction

Describe the Link Reaction

• two pyruvate molecules are transported to mitochondria

• pyruvate is converted into Acetyl-CoA

• this releases CO₂ and forms electron-carrying molecules

3rd Stage of Aerobic Respiration

the Kreb’s cycle

Describe the Kreb’s cycle

• Acetyl-CoA undergoes a series of chemical reactions

• this produces 2 ATP molecules, CO₂ and electron-carrying molecules

4th stage of Aerobic Respiration

Oxidative Phosphorylation

Describe oxidative phosphorylation

• electron-carrying molecules deliver electrons to electron transport chain in cristae

• ATP synthase produces ~32-34 ATP

• uses oxygen to form water

Structure of chloroplasts

• double membrane

• thylakoids stacked into grana to increase SA:V for optimised light absorption

• stroma contains enzymes and DNA

Function of vacuoles in plant cells

• stores water

• maintains turgor pressure

function of vacuoles in animal cells

• temporary structures

• stores and transports water, nutrients, and sugars

• stores and transports waste products and toxins

function of vesicles

• transports substances around cell

• performs endocytosis and exocytosis

• stores proteins, lipids, enzymes, hormones, and neurotransmitters

Structure of Golgi apparatus

• flattened membrane sacs

function of Golgi apparatus

• modifies proteins

• sorts proteins

• packages proteins

• produces vesicles

Components unique to rough endoplasmic reticulum

• ribosomes embedded to the outer surface

• primary site of protein synthesis (because it contains ribosomes)

components unique to smooth endoplasmic reticulum

• no ribosomes

• stores calcium

• detoxification

• responsible for membrane formation

• hosts the enzymes necessary to construct essential fat-based molecules

function of ribosomes

• site of protein synthesis

• translates mRNA into amino acid chains

function of lysosomes

• contains digestive enzymes

  • breaks down pathogens

  • recycles organelles

  • digests waste materials

function of cytoskeleton

• maintains cell shape

• supports organelle movement and structure

• assists intracellular transport

Structures unique to plant cells.

• cell wall

• chloroplasts

• large central vacuole

Structures common to plant AND animal cells

• cell membrane

• ribosomes

• mitochondria

• cytoplasm

• nucleus

• Golgi apparatus

• ER

Autotrophs

• produce organic substances from inorganic sources

• this organic substance is food

• undergo photosynthesis

heterotrophs

• acquire food by consuming other animals (could be both autotrophs and other heterotrophs)

photosynthesis equation

6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂

Why is photosynthesis important?

• converts light energy to chemical energy

• produces glucose

• produces oxygen

• forms the basis of all food chains

Aerobic respiration equation

C₆H₁₂O₆ + 6O₂ —> 6CO₂ + 6H₂O + ATP

where does aerobic respiration occur?

• glycolysis = cytoplasm

• Kreb’s Cycle = mitochondrial matrix gel

• Electron Transport chain: cristae (inner mitochondrial membrane)

Unique to Aerobic respiration

• occurs in the presence of oxygen

• yields 36-38 ATP

• highly efficient

• produces CO₂ and H₂O

Unique to anaerobic respriration

• occurs in the absence of oxygen

• yields 2 ATP

• low efficiency

• produces lactate or ethanol

Fermentation in plants and yeast

C₆H₁₂O₆ —> C₂H₅OH + CO₂ + ATP

Fermentation in animals

C₆H₁₂O₆ —> C₃H₆O₃ + ATP

Components of ATP

• adenine

• ribose

• three phosphate groups

Formation of ATP equation

ADP + Pi + Energy —> ATP

• energy is stored in phosphate bond

Why is ATP called the energy currency of cells?

it transfers energy from respiration to metabolic reactions

Define diffusion

• the passive transport of particles from an area of higher concentration to an area of lower concentration.

• It continues until the particles are evenly distributed, requiring no external energy input

Define facilitated diffusion

• the passive movement of molecules across a cell membrane from an area of higher concentration to an area of lower concentration

• with the assistance of specific membrane proteins

• channel and carrier proteins deliver molecules

Define osmosis

• movement of water across a selectively permeable membrane from a area of high water concentration to an area of low water concentration

Define active transport

• the movement of molecules or ions across a cell membrane from an area of low concentration to an area of high concentration

key characteristics of active transport

• requires ATP

• moves against the gradient

• relies on specialised pumps

• maintains precise internal concentration of molecules

endocytosis

• an active transport process where a cell engulfs external materials by wrapping its cell membrane around them to form a pocket

• this pocket pinches off inside the cell to create a vesicle

Define exocytosis

• an active transport process where a cell expels materials by fusing a membrane-bound vesicle with the outer cell membrane

• This fusion opens the vesicle, releasing its contents into the surrounding extracellular space

What are channel proteins?

• proteins that form pores

• these pores allow ions or water to pass through

What are carrier proteins?

• proteins that change shape

• this enables them to transport substances through the membrane

What is a concentration gradient?

• difference in concentration between two regions

• greater gradient = faster diffusion

Why is SA:V important?

• faster exchange of materials

• enables for more efficient diffusion

How does molecule size affect membrane transport?

• small/non-polar particles diffuse easily

• large/charged particles do not diffuse easily and need carrier and channel proteins

What is a metabolic pathway?

• a sequence of enzyme-controlled reactions that converts substances into products

What are characteristics of metabolic pathways?

• many regulated steps

• requires specific enzymes

• intermediate products are forms

• some energy is lost as heat

How do mitochondria facilitate metabolism?

cristae increase membrane surface area for electron transport and ATP production

How do chloroplasts facilitate metabolism?

thylakoid membranes provide large surface area for light-dependent reactions

How do environmental factors affect metabolism?

• disrupts regulation of hormones

• interferes with production of energy

• triggers epigenetic modifications

What environmental factors affect metabolism?

• temperature

• pH

• substrate concentration

• oxygen availability

Why must DNA replicate before cell division?

ensures each daughter cell receives a complete set of genetic information

Describe binary fission

• a method of asexual reproduction

• single parent cell splits into two identical daughter cells

Describe DNA replication in Binary Fission

• the single circular bacterial chromosome uncoils

• the cell copies its entire strand of DNA

• this creates two genetically identical daughter cells

Describe cell elongation in Binary fission

• the cell grows longer to prepare for division

• the two identical DNA loops move towards opposite poles of the cell

• the cytoplasmic membrane begins to expand

Describe septum formation in Binary Fission

• a pinching occurs at the cell’s midpoint

• a division wall begins to grow inwards

Describe cell wall development in Binary Fission

• the division wall fully matures across the centre

• new cell wall and plasma membrane material deposit along the division wall

• the cytoplasm becomes completely partitioned into two distinct zones

Describe cytokinesis in Binary Fission

• the parent cell splits down the middle of the division wall

• two independent, genetically identical daughter cells are released

• each new cell functions as an individual organism

What is mitosis?

Nuclear division producing two genetically identical diploid daughter cells

Stages of mitosis

PMAT

Describe prophase in mitosis

• linear chromatin condenses into distinct sister chromatids

• constructs a microtubule spindle within a dissolving nucleus

Describe metaphase in mitosis

• highly condensed sister chromatids line up along the cell’s equator

• they are securely tethered to opposite spindle poles via kinetochores

Describe anaphase in mitosis

• cohesion proteins are cleaved

• shortening kinetochore microtubules and sliding polar microtubules pull identical chromatid sisters to opposite poles of the cell

Describe telophase in mitosis

• identical chromosomes uncoil back into loose chromatin at opposite poles

• new nuclear envelopes and nucleoli reform around the identical chromosomes

• mitotic spindle deconstructs

Products of mitosis

• 2 genetically identical diploid daughter cells

What is meiosis?

• two stage division

• produces four genetically unique haploid cells

Products of meiosis

• 4 genetically unique haploid gametes

Define diploid

• two chromosome sets

Define haploid

• one chromosome set

Why is crossing over important during prophase 1?

• exchange of DNA between homologous chromosomes creates genetic variation

What is independent assortment?

• random orientation of homologous chromosome pairs during metaphase 1

• produces unique gametes

Why is fertilisation important?

• restores diploid chromosome number and increases genetic variation

Stages of interphase in the cell cycle

• G1

• S

• G2

Stages of M phase in the cell cycle

• mitosis

• cytokinesis

What happens during G1?

• cell growth and protein synthesis

What happens during S phase?

• DNA replication occurs

What happens during G2?

• further growth and preparation for mitosis

What is the purpose of cell cycle checkpoints?

ensures:

• DNA integrity

• proper chromosome replication

• correct spindle attachment

How can hormones regulate cell division?

• hormones act as signalling molecules that stimulate or inhibit cell division