Biology Exam Sem 1 Content

What is the purpose of Cell Replication (GRPH)

1. Growth - organisms need to grow
2.Repair - old cells need to be replaced
3. Procreation - survival of species
4. Hereditary - passing on genetic information

Binary Fission (prokaryote procreation)

1. Replication of circular DNA
2. 2 circular chromosome moves to opposite ends
3. Cell membrane pinches a new septum

Eukaryotic cell cycle

G1 phase - Cell prepares new proteins, carries out normal tasks, ends when DNA replicates
S phase - DNA replication occurs (chromosomes duplicate
G2 phase - Preparation for cell division
M phase - mitosis
Interphase is considered all but M phase

What is G0 phase

If the cell does not receive the go ahead for G1, it goes to G0 where it does not replicate.

What happens in S phase

Yes DNA replicates, but it does this through division of chromosomes forming two long chains joined by a centromere. Each copy of this chain is called a chromatid

Prophase

- Nuclear membrane dissolves
- Chromatid tightly coil and become chromosomes, joined by a centromere
- Centrioles move away from the nucleus in opposite directions

Anaphase

- Spindle fibres contract, as a result, chromatids of each chromosome are pulled to either end of the cell
- Once separated, they are each considered chromosomes

Metaphase

Chromosomes line up and down the centre of the cell, each attach to spindle fibres

Telophase

Once at the end of cell, Chromosomes transform back into chromatin. Nuclear membrane reinforces arround each nucleus

Cytokenesis

Occurs following mitosis
- In animal cells, cytoplasm divides through 'cleavage' process, cell membrane draws together to form cleavage furrow
- In plant cells - A new cell wall must form around each daughter cell

Cell growth checkpoints

At each checkpoint of the Eukaryotic cell cycle, cyclins and cyclin-dependent kinases (CDK) act as gatekeepers and check cells at the G1 and G2 checkpoints. If conditions are not met, CDK's will stop cell growth until DNA is repaired

What is checked at the G1 checkpoint?

cell size, nutrients, growth factors, DNA damage

What is checked at the G2 checkpoint?

DNA damage, DNA replication completeness

Mitotic checkpoint

Checks for Chromosome misalignment and separation

Cyclin molecule

Promotes cell growth and allows cell to continue growing in cell cycle

CDK molceule

- Some CDK's promote cell growth
- Some inhibit if irregular growth occurs

What do proto-oncogenes do?

code for proteins that
- stimulate cell division
- stop cellular differentiation
- stop apoptosis
Excessive amounts can cause a tumour

What do tumor suppressor genes do?

Code for proteins that
- slow down cell growth
- Repair DNA damage
- Initiate apoptosis

Steps of apoptosis (programmed cell death)

1. Enzymes are shred into DNA fragments
2. Nucleus is dismantled and membrane inflates creating blebs :)
3. Apoptopic blebs are consumed by phagocytic cells using endocytosis

What does the p53 gene do?

When damaged DNA is found, it either
a) pauses the cell cycle to fix the DNA
b) Apoptosis damaged cell
Either way, genetic stability is ensured

The BRCA genes

ARE TUMOR suppressor genes that inhibit tumor growth \-- so when they mutate they lose their ability to suppress tumors\--- this leads to tumors....
If is inherited, DNA cannot be repaired leading to abnormal cell growth

What are mutations?

Change in DNA within chromosomes that can have great effect on production of correct proteins

What are mutagens?

- An agent/ substance that can cause mutation. A mutagen directly changes DNA code that codes for required proteins

Consequences of Chemical mutagens e.g carcinogens

Chemical directly changes DNA code, altering protein production

Consequences of physical mutagens e.g UV light, X-ray

causes alterations to DNA code

Consequences of biological mutagens e.g viruses

Viral DNA is inserted directly into host cell DNA Code, changing the cells gene and function

Cell Differentiation!

- Creation of a new organism always begins with once cell
- From this zygote, many mitotic divisions occur to specialise and differentiate cells

What stem cells are produced in days 1-5 of differentiation

Totipotent cells - can be all types of cells (In Zygote)

What stem cells are produced in days 5 of differentiation

Pluripotent cells - can differentiate into all but embryonic membrane cells (In blasocyst)

What stem cells are produced up to 2 months into differentiation

Multipotent cells - can differentiate into many cell types but not all (In embryo)

At formation of the blasocyst, three distinct cell germ layers are designated

Ectoderm - skin cells, brain neurons, hair follicles
Mesoderm - All muscle cell, cartilge and connective tissue
Endoderm - Digestice tract cells, urinary and bladder cells

Stem cell therapy

Umbilical cord stem cell + Adult stem cells (bone marrow) are multipotent, Embryonic stem cells are pluripotent.
Bone marrow can treat leukaemia

Cell Theory

1. All organisms are composed of cells
2. The cell is the most basic unit of structure within organisms
3. All cells come from pre-existing cells

Features with Prokaryotic and Eukaryotic cells

Size of cell, prokaryotic 1-2µm, Eukaryotic 10-100µm
Chromosomes prokaryotic, singular, Eukaryotic in paris

Differences between animal and plant cells

Only plants cells have chloroplasts
Both have vacuoles but animals have one big oen and animals have many small ones
Plant cells have a cell wall

Diffusion

net movement of particles from an area of higher concentration to an area of lower concentration

What is an optimal SA:V ratio

high Surface area \= more points for diffusion
low volume \= less distance travelled by nutrients

What factors can influence SA:V

Changing shape - folds/long skinny shapes increase SA
Organelles - can press other organelles close to membrane e.g plant cell vacuole

Which organelles synthesise protein?

Ribosomes! made up of two subunits and allow information to be used to synthesise proteins. Only organelle found in prokaryotes

What are proteins?

Made up of sequence of amino acids
Needed for growth, repair, carrying molecules, communication

The Nucleus

Contains DNA
Porous double layered nuclear membrane
Nucleolus contains RNA

Mitochondria

Site of cellular respiration where glucose is converted to ATP for energy
- Has its own DNA
- consists of cristae (folds of the mitchondria)

What is the key organelles that facilitates protein transport, how generally does it do this

Endoplasmic Recticulum, facilitates protein synthesis, Can pinch off membrane to create sacs to move protein out of cell

Rough Endoplasmic Reticulum (RER)

- Involved in transport of proteins, ribosomes are attached to it
- Proteins synthesised by ribosomes are modified and transported here

Smooth Endoplasmic Reticulum (SER)

- site of lipid, (fat) synthesis and transport
- Makes product that is used inside the cell, also detoxifies harmful product

What are the organelles involved in enzyme storage and packaging

Golgi aparatus, vesicles, lysosomes, peroxisomes

What is the role of the Golgi apparatus?

Modifies, sorts, and packages proteins. Vesicles pinch off and exit cell

What are vesicles

membranous sacs that are used to transport materials in the cell

What is the role of lysosomes?

They contain digestive enzymes to break down larger materials such as proteins, lipids
These enzymes can break down excess macromolecules and non-functioning organelles

What are three cell structure and support mechanisms within a cell

Microtubules - scaffold a cell, hollow tubes
Centrioles - Attach to spindle fibres in mitosis
Microfilaments - Found in tight bundles, contract and change the shape of a cell.

What is the role of Chloroplast

- Contains green chlorophyll which helps absorb energy from the sun
- Photosynthesis takes place in the liquid stroma and the thylakoid membranes in the chloroplast
- Stacks of thylakoid membranes called grana means lots of SA for photosynthesis to occur

What are chromoplasts

Contain coloured pigments other than green.]
Carotid - red green colour

What does the vacuole do in a plant cell?

- Because of its size, it provides structural support
- Used as storage place for minerals and vitamins

Cell Wall

provides another layer of protection and structural support. In plant cells, made out of cellulose

Purpose of the Plasma Membrane (PMCT)

- Protects the cell from foreign bodies
- Maintains intracellular environment
- Communicates with the external environment
- Facilitates Transport between intra and extra cellular environments.

What is the phospholipid bilayer?

Two layers of phospholipids with hydrophilic heads on the outside and hydrophobic tails on the inside

What is the role of Cholestrol in the Bilayer

- maintains space between fatty tail acids
- Prevents phosphlipids from moving too far or binding too tight; keeps layer flexible

Transport proteins

Involved in moving substances through the membrane
- Channel proteins for ions and small molecules (passive)
- Carrier proteins for larger molecules o against concentration gradient (active)

Semipermeability of the membrane

Small, non-polar ions can pass through the layer without proteins i.e oxygen, CO2
Charged Ions and large molecules (proteins and glucose) require transport proteins

Active vs Passive transport

active needs energy; passive does not need energy (diffusion).
Active moves against concentration gradient, passiev goes with it

What is facilitated diffusion?

Channel Proteins - Allows specific ions to pass through. Forms a pore to enable fast transport
Carrier Proteins - Involved of large transport such as sugars or amino acids

What is osmosis?

The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration (passive)

What is osmotic potential?

A measure of the potential of water to move between two regions of different concentration.

What are hypertonic solutions

- Solute concentration is greater outside
- Water concentration is greater inside cell

What are isotonic solutions?

Solute and hence water concentrations are equal

What are hypotonic solutions

- Solute concentration is lower outside
- Water concentration is lower inside

bulk transport

The process by which large particles and macromolecules are transported through plasma membranes through exocytosis and endocytosis

Vascular Plants Topic

Either shoot (above ground) or root (below ground)

merismatic tissue

- Actively growing root and shoot tips
- Increases length
- Cells are able to undergo mitotic division

Permanent Tissues

Cells no longer able to divide e.g
- Dermal tissue (skin protecting plant from water loss)
- Ground tissue (for photosynthesis support)
- Vascular tissue (for trasnport xylem, phloem)

What is parenchyma?

Functional, living tissue, which is thin walled and makes up photosynthetic cells in leaves and starch storage in roots

What is sclerenchyma tissue?

Tissue thickened with woody, hard cell walls to provide strength

What is collenchyma tissue?

Tissue thickened with cellulose cell walls to provide support & structure, living, and elongated

The Root System

All of the roots of a plant, responsible for anchoring and absorption of water. Roots are surface for absorption with root hairs increasing SA:V

How water is taken up through the root system

1. Root hair penetrates between soil particles and are immersed in water
2. Water moves through epidermal cell wall and plasma membrane
3. Water & dissolved minerals enters by osmosis, diffusion and active transport
4. The water then moved to parenchyma cells under the epidermis which makes up the main root body.(Vascular Bundle)

role of xylem and phloem

Xylem transports water, nutrients and minerals with tubular, elongated walls
Phloem has thin walls which transports sugars and hormones

What are tracheids? (Xylem)

long, thin, tapered cells found in the xylem of all vascular plants. Have pits to allow lateral movement of water

What are vessels (Xylem)

In flowering plants only
Dead, pipe-like structues that have perforation plates between vessel and pits like in tracheids where water can leave xylem

Epithelial Tissue

- Sheets of cells that cover internal/ external surfaces i.e skin, tube linings

What does muscle tissue do?

Contract and enable movement. Skeletal: in arms and legs. Smooth: in gut

Connective Tissue

Provide strutural support
E.g cartilage + bone

Nervous tissue

Responsible for involuntary movement, made of neurons. e.g nerves along the spine

What are the four main roles of the digestive system?

Ingestion, Digestion, Absorption of nutrients, Excretion

Ingestion

Food enters somewhere i.e through the mouth

Digestion

The breakdown of complex organic molecules into smaller components via mechanical means. Begins immediately once food enters the mouth

What digestion happens in the mouth

Mechanical - mastiation (chewing), teeth and tongue grind food to smaller pieces
Chemical - Amylase released in saliva and turns complex carbs into maltose.

What does chewed up food and saliva create and what happens to it

It creates bolus which is then pushed down oesophagus by tongue through swallowing reflex. Epiglottus prevents bolus from entering respiratory tract

What is the process of the oesophagus

Peristalsis - Involuntary contractions of circular muscle tissue relax and contract to move bolus down.

What are sphincters?

Large bands of circular muscle tissue that regulate movement of food and other substances
- mostly involuntary

What is the function and location of the Upper Oesophageal Sphincter?

It prevents air from entering the oesophagus
It prevents reflux of oesophageal contents
Location: Guards entrance of oesophagus

Lower oesophageal sphincter (LOS)

Stops acidic contents from travelling up oesophagus
Location: between oesophagus and stomach

pyloric sphincter

Controls chyme into the small intestine
Location: between stomach and small intestine

What are the processes of mechanical and chemical digestion within the stomach

Mechanical: stomach walls relax and contract to break down food by increasing SA creates CHYME
Chemical: gastric juice breaks down bolus. Made from Mucus, water, HCl, Pepsin and protease enzymes.

What is absorbed in the stomach?

Nothing except panadol and alcohol

Parts of the small intestine + brief function summary

Duodenum - Site of most digestive action, helped by pancreas, liver and gallbladder
Jejunum - finishes chemical digestion
Ileum " "

What are the four pancreatic secretions (BLAT)

Bicarbonate - Neutralises activity of chyme as it enters small intestine (counteracts pepsin)
Lipase - Fats --\> Glycerol + Fatty acids
Amylase - Complex carbs --\> maltose
Trypsin - Long Peptide chains --\> short pep. chains

Jejunum + Ileum secretions

Maltase - Maltose --\> glucose
Petidase - short pep. chains into amino acids

How do villi increase the efficiency of absorption?

More SA \= more absorption
thin lining, blood vessels close by allows quick uptake
microvilli ++SA

Capilary Networks + lacteals and what do they absorb

Every villi has one which is then intertwined around a lacteal (lymph vessel)
Glucose + Amino Acids are absorbed by capilaries
Fatty Acids + Glycerol absorbed by lacteals

Large Intesine

Consist of colon and rectum but only colon absobs stuff