SECTION 2

What extra organelles do plants have?

Cellulose cell wall / vacuole / chloroplasts

What are the ‘channels’ (for exchanging substances) in cellulose cell walls called?

Plasmodesmata

What do plants use to store excess sugars?

Starch grains

What are the 2 key differences between plant cells and fungal cells?

Cell walls are made of chitin / Do not have chloroplasts

What is the function of cell-surface membrane?

Regulates the movement of substances in and out of the cell

What is the function of the nucleus?

Control cell activities / hold genetic information

What are the 4 parts of the nucleus?

Nuclear envelope / nucleolus / nuclear pore / chromatin

What is the function of the mitochondria?

Site of aerobic respiration where ATP is produced.

What is the function of the golgi apparatus?

Process and packages new lipids and proteins / make lysosomes

What is the function of ribosomes?

A site where proteins are made

What is the function of rough endoplasmic reticulum?

Fold and processes proteins

What is the function of smooth endoplasmic reticulum?

Synthesis and processes lipids

What is the function of the cell wall?

Supports cells and prevent them from changing shape

What is the function of the vacuole? (there’s 4 😁)

Maintain pressure inside cells / keep cells rigid / stops wilting / isolate unwanted chemicals.

What are the finger-like projections on epithelial cells called?

Villi

Define tissues

A group of cells working together to perform a particular function

Define organ

Different tissues work together to form organs

What part of a bacterial cell can carry the genes for antibiotic resistance?

The plasmids

Describe the process of binary fission

Circular DNA and plasmids replicate / move to opposite poles / cell gets bigger / cytoplasm divides and new cell wall forms

What is magnification?

How much bigger the image is than the specimen

What is the equation for magnification?

Size of image / size of real object

What is resolution?

How well a microscope distinguish between two points that are close together

What are the 2 types of microscopes?

Optical and electron

What do electron microscopes use to form an image?

Electrons

What is the maximum resolution for electron microscopes?

0.0002 micrometres

What is the maximum useful magnification of an electron microscope?

x 1500000

What organelles can you see with an optical microscope?

Nucleus / mitochondria

What are the 2 types of electron microscope?

Scanning and Transmission

What do TEMs do to form an image?

Use electromagnets to focus a beam of electrons, which is then transmitted through the specimen

What do SEMs do to form an image?

Scan a beam of electrons across the specimen, knocking off electrons from the specimen which is then gathered in a cathode ray tube to form an image.

How do you prepare a ‘temporary mount’?

Pipette small drop of water on slide / place thin section of specimen on water drop / add stain / add cover slip using mounted needle

What stain could you add to highlight the cytoplasm of a cell?

Eosin

What stain could you add to highlight the starch grains of a cell?

Iodine in potassium iodide solution

Describe how you can place a cover slip on the slide

Stand cover slip upright next to water droplet / tilt and lower onto the water droplet without forming any air bubbles

Suggest how may you remove air bubbles in water?

Boil the water

What are the key 3 steps of cell fractionation? (in order)

Homogenisation / filtration / ultracentrifugation

What does homogenisation mean?

Breaking up the cells

Suggest 2 methods of homogenisation

Vibrating the cells / grind cells up in a blender

What are the 3 conditions in homogenisation?

Solution must be isotonic / kept ice cold / buffered

What does isotonic mean?

Have the same concentration of chemicals as the cells being broken down

Why should the solution be isotonic during homogenisation?

Prevent damage to organelles through osmosis

Why should the solution be ice-cold during homogenisation?

Reduce enzyme activity that may break down organelles

How are homogenised cell solutions filtered?

Through a gauze

What is removed when a homogenised cell solution is filtered?

Large cell debris / tissue debris

What are the names of the 2 layers formed by ultracentrifugation? (specify top / bottom)

Top= supernatant / bottom= pellet

What does genetically identical mean?

Have an exact copy of the DNA of the parent cell

What is the period of cell growth and DNA replication called?

Interphase

What are the 3 parts of interphase? (in order)

Gap phase 1 / synthesis / gap phase 2

What happens in gap phase 1 in interphase?

Cell grows and new organelles and proteins are made

What happens in gap phase 2 in interphase?

Cell keeps growing and proteins needed for cell division are made

What happens in synthesis in interphase?

Cell replicates its DNA ready to divide by mitosis

What are the 3 main things that happen in interphase?

DNA unravel & replicated / organelles replicated / ATP content increased

What happens in prophase?

Chromosomes condenses & gets shorter / appear as 2 sister chromatids joined at the centromere

What happens in metaphase?

Chromosomes line up along the equator / attaches to spindle fibres by their centromere

What happens in anaphase?

Centromere divides / spindles contract / sister chromatids are pulled to opposite poles of the cell / appear v shaped

What happens in telophase?

Chromosomes uncoil / become long again / nuclear envelope forms around each group of chromosomes / cytoplasm divides

What is the name of cytoplasm dividing?

Cytokinesis

What are mitosis and cell cycle controlled by?

Genes

How could [stopping the synthesis of enzymes] stop tumours from dividing?

Cell would be unable to enter the synthesis phase, disrupting cell cycle and forcing cell to kill itself

What is the equation for mitotic index?

Number of cells with visible chromosomes / total number of cells observed

Why was the membrane bilayer considered ‘fluid’?

Phospholipids are constantly moving

What are lipids with polysaccharide chains called?

Glycolipids

What does cholesterol do for phospholipid membrane?

Make membrane less fluid and more rigid / help maintain shape of animal cells

How does cholesterol make membranes less fluid / more rigid?

They bind to hydrophobic tails of the phospholipids, causing them to pack more closely together which restricts movement of phospholipids

What happens to membrane permeability when temperature below 0?

Membrane becomes rigid / closely packed together / may cause transport proteins to deform which increase permeability / ice crystals may form & pierce membrane

What happens to membrane permeability when temperature between 0-45?

Membrane is partially permeable / as temp increase, permeability decreases as theres more kinetic energy

What happens to membrane permeability when temperature is above 45?

Bilayer starts to melt (breakdown) / water inside cell expands, putting pressure on membrane / transport proteins denature, cannot control movement / permeability increases

What are antigens?

Molecules that can generate an immune response

What are the 2 things phagocytes can do?

Engulf pathogens / Activate T-cells

What is the bubble containing a pathogen in the cytoplasm of a phagocyte called?

Phagocytic vacuole

How does the phagocyte destruct the phagocytic vacuole?

A lysosome contained lysozymes fuse with phagocytic vacuole / breaking the pathogen down.

How does a phagocyte initially engulf a pathogen?

The cytoplasm of the phagocyte moves round the pathogen

How does a phagocyte know when to engulf an antigen?

Recognition of foreign antigens on the pathogen