Cell Biology - Body Systems and Biology

Week 1

What are the 3 Domains of life?

Bacteria, Archaea, Eukayota

Are Bacteria Prokaryotic or Eukaryotic?

Prokaryotic

What is the bacterial cell wall made of?

Murein

How is bacterial DNA organised?

A single loop of DNA without histones (Protein that provides structural support support and helps organize long strands of DNA inside a cell's.

What makes Archaea different from Bacteria?

Their genes/protein synthesis resemble eukaryotes, and they lack murein.

What type of membrane linkage do Archaea have?

Ether linkages between fatty acids and glycerol.

What is special about archaeal RNA polymerase?

It is more complex than bacterial RNA polymerase

What organelles are found in eukaryotic cells?

Membrane-bound organelles such as mitochondria and chloroplasts

What type of membrane linkage do Eukaryota have?

Ester linkages between fatty acids and glycerol.

Do all eukaryotic cells have a cell wall?

No. When present, it contains no murein.

Compare the 3 Domains of life

Bacteria: 70S ribosomes + murein cell wall + DNA loop
Archaea: 70S ribosomes + NO murein + ether-linked membranes
Eukaryota: 80S ribosomes + membrane-bound organelles + ester-linked membranes

How large are prokaryotic cells?

About 0.5–5 μm, smaller than animal cells.

How is DNA arranged in a prokaryotic cell?

Circular DNA in the nucleoid, plus plasmids.

What is the prokaryotic cell wall made of?

Murein

What are the key features of a prokaryotic cell?

Small, no membrane-bound organelles, circular DNA, 70S ribosomes, murein wall, and often capsule/flagellum.

Why are plant cells usually more regular/rectangular than animal cells?

The rigid cell wall gives them a fixed shape.

Why do plant cells need a cell wall and chloroplasts?

Plants need to stay rigid and produce their own food.

What is the fungal cell wall made of?

Chitin.

Do fungal cells have chloroplasts?

No. Fungi are not photosynthetic.

How do fungi obtain nutrients?

They absorb nutrients from other sources.

What is the function of the large vacuole in fungal cells?

Storage and regulation of internal conditions.

What are fungal buds?

New cells formed by asexual reproduction.

What is the size of a prokaryotic cell?

→ 0.5–5 μm

What is the size of a eukaryotic cell?

10 -30mμ.

What is the main difference in organelles?

Prokaryotes have no membrane-bound organelles eukaryotes do.

How does the DNA differ?

Prokaryotes: circular DNA. Eukaryotes: linear DNA inside a nucleus.

What is the prokaryotic cell wall made of?

Murein.

Which eukaryotic cells have a cell wall?

Plant cells.

What structures can some animal cells have for movement?

Cilia.

How are animal cells different from plant cells in terms of vacuoles?

Animal cells have numerous small vacuoles; plants have one large central vacuole.

Do plant cells have lysosomes?

No; they use other mechanisms for breaking down materials.

Do plant cells have centrioles?

No; they use another mechanism for cell division.

Do fungi have lysosomes?

Yes.

Do fungi have centrioles?

No; they use another mechanism.

What is osmotic lysis?

Cell shrinking or bursting due to loss or gain of water.

What type of substances can cross the cell membrane by simple diffusion?

Lipid-soluble substances.

What is facilitated diffusion?

Movement of substances across the membrane using transmembrane proteins.

What is active transport?

Movement of substances across the membrane using carrier proteins and requiring energy.

What is osmosis?

Movement of water across the membrane through aquaporins.

What are aquaporins?

Membrane proteins that allow water to cross the cell membrane.

What other functions does the cell membrane have besides controlling transport?

Provides structural support and allows cell signalling.

Which membrane components are involved in cell signalling?

Glycoproteins and glycolipids.

What is the cytosol?

The fluid component of the cytoplasm in which biochemical reactions occur.

What organic compounds can be stored in the cytoplasm?

Glycogen and triglyceride (fat) droplets.

What types of inorganic substances are found in the cytoplasm?

Inorganic ions.

What genetic material is stored in the nucleus?

DNA, organised into chromosomes.

How does the nucleus control protein synthesis?

DNA is used to produce mRNA, which carries the instructions for protein synthesis.

What does the nucleus produce that is needed to make ribosomes?

Ribosomal RNA (rRNA) and ribosomes.

What is special about the outer nuclear membrane?

It is continuous with the endoplasmic reticulum and often has ribosomes on its surface.

What is the function of nuclear pores?

Allow large molecules, such as mRNA, to pass into and out of the nucleus.

What is nucleoplasm?

The granular, jelly-like material that makes up most of the nucleus.

What is chromatin?

DNA associated with histone proteins within the nucleoplasm, forming chromosomes.

What is ATP?

The main energy-carrying molecule used by cells.

Why do high-metabolic cells have more mitochondria and cristae?

To increase their capacity to produce enough ATP.

Give examples of cells with high numbers of mitochondria.

Muscle cells and epithelial cells of the digestive tract.

What are cristae and why are they important?

Shelf-like folds of the inner mitochondrial membrane

They increase surface area for enzymes involved in respiration, allowing greater ATP production.

Why can mitochondria produce some of their own proteins?

They contain their own DNA and protein-making machinery.

What do chloroplasts use to carry out photosynthesis?

Light energy, water (H₂O), and carbon dioxide (CO₂).

What does photosynthesis produce?

Glucose and oxygen (O₂).

Where does the first stage of photosynthesis occur?

In the thylakoid membranes/grana.

What is the main structural difference between rough and smooth ER?

Smooth ER lacks ribosomes on its surface.

Which cells have extensive endoplasmic reticulum?

Cells that synthesise and store large amounts of carbohydrates, proteins or lipids.

Give examples of cells with extensive ER.

Liver cells and secretory cells, such as epithelial cells of the small intestine.

Where do peroxisomes originate from and what enzyme found in them?

They stem from the smooth endoplasmic reticulum.

Catalase.

What are the main functions of peroxisomes?

Break down fatty acids and detoxify harmful substances.

What harmful substance can peroxisomes detoxify?

Hydrogen peroxide (H₂O₂).

What does catalase do?

Breaks down hydrogen peroxide into harmless products

What does the Golgi add to proteins to form glycoproteins?

Carbohydrates

What organelles does the Golgi help form?

Lysosomes, which contain digestive enzymes for breakdown and recycling.

In which cells is the Golgi especially prominent?

Secretory cells, such as cells in the small intestine.

Where are lysosomes formed?

From vesicles produced by the Golgi apparatus.

What enzymes are found in lysosomes?

Digestive enzymes such as lipases and proteases.

How do plant and animal cell vacuoles differ?

Plants have one large vacuole; animals have small, temporary vacuoles.

What is the organisation hierarchy in living beings?

→ Cell → tissue → organ → organ system → organism.

What defines each level of organisation?

• Cells – the basic structural and functional units of life.

• Tissues – groups of similar cells working together to perform a particular function.

• Organs – structures made of different tissues working together to carry out specific functions.

• Organ systems – groups of organs working together to perform major physiological processes.

• Organism – the complete living individual.

Why do cells become specialised?

To have structures and organelles suited to their specific function.

How do cells become specialised during development?

Initially similar embryonic cells differentiate into specialised cell types.

Where do the cells of a multicellular organism originate?

From mitotic divisions of the fertilised egg.

What are housekeeping genes?

Genes expressed in all cell types for essential cellular processes.

What do housekeeping genes code for?

Proteins needed for processes such as DNA replication and respiration

Are viruses cellular or acellular?

Acellular; they lack normal cellular structures.

What genetic material can viruses contain?

Either DNA or RNA.

Why can viruses only replicate inside host cells?

They rely on host-cell machinery to replicate.

How do viruses enter and adapt to host cells?

Attachment proteins enable entry; mutations can alter these proteins.

What are the core processes a cell must carry out?

Replication, transport, energy production and protein synthesis.

What is cellular homeostasis?

Maintaining stable internal conditions, e.g. water balance and pH.

What is cell signalling?

Cells communicate using signals such as neurotransmitters or hormones acting on receptors.

What are the three stages of interphase?

G1, S phase and G2.

What happens during G1, S and G2?

G1: cell growth. S: DNA replication. G2: growth, chromosome checking and repair.

Define chromosomes

A structure of DNA wrapped around histone proteins that carries genetic information.

What are somatic cells?

Body cells, excluding sex cells.

What are sister chromatids?

Two identical copies of a replicated chromosome joined at a centromere

What are the four stages of mitosis?

→ Prophase → Metaphase → Anaphase → Telophase.

What happens to sister chromatids during mitosis?

They separate and are evenly distributed into two daughter cells.

What is Mitosis?

Mitosis is the division of diploid somatic (body) cells to produce two genetically identical daughter cells with the same number of chromosomes. Each chromosome consists of two sister chromatids joined at a centromere, which separate during mitosis. Mitosis is essential for growth, tissue repair and asexual reproduction. It has four stages: prophase, metaphase, anaphase and telophase (PMAT).

What happens during Prophase?

Chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at a centromere.

The mitotic spindle begins to form as centrosomes move towards opposite poles.

The nucleolus disappears, and the nuclear envelope breaks down as mitosis progresses.

What happens during interphase?

Chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at a centromere.

The mitotic spindle begins to form as centrosomes move towards opposite poles.

The nucleolus disappears, and the nuclear envelope breaks down as mitosis progresses.

What happens during Metaphase?

Chromosomes are thick and condensed, each consisting of two identical sister chromatids joined at a centromere. Spindle fibres align the chromosomes along the equator of the cell, called the metaphase plate.

What happens during Anaphase?

Centromeres divide, separating sister chromatids, which are pulled by spindle fibres towards opposite poles of the cell. Mitochondria provide energy for this process.Each pole receives one complete set of chromosomes.

What happens during Telophase?

Chromosomes reach opposite poles and uncoil into chromatin. Spindle fibres break down, the nucleolus and nuclear envelopes reform, and cytokinesis divides the cytoplasm to produce two genetically identical daughter cells.